Transcriber’s Note: Italics are enclosed in _underscores_. Additional
notes will be found near the end of this ebook.




PHILOSOPHY




                               PHILOSOPHY

                                  _By_
                            Bertrand Russell


                             [Illustration]


                                NEW YORK
                     W · W · NORTON & COMPANY, INC.
                              _Publishers_




                            Copyright, 1927,
                            BERTRAND RUSSELL

 Published in Great Britain under the title “An Outline of Philosophy”


                PRINTED IN THE UNITED STATES OF AMERICA
                FOR THE PUBLISHERS BY THE VAN REES PRESS




CONTENTS


  CHAPTER                                                           PAGE
      I.  PHILOSOPHIC DOUBTS                                           1


  PART I

  MAN FROM WITHOUT

     II.  MAN AND HIS ENVIRONMENT                                     16

    III.  THE PROCESS OF LEARNING IN ANIMALS AND INFANTS              29

     IV.  LANGUAGE                                                    43

      V.  PERCEPTION OBJECTIVELY REGARDED                             58

     VI.  MEMORY OBJECTIVELY REGARDED                                 70

    VII.  INFERENCE AS A HABIT                                        79

   VIII.  KNOWLEDGE BEHAVIOURISTICALLY CONSIDERED                     88


  PART II

  THE PHYSICAL WORLD

     IX.  THE STRUCTURE OF THE ATOM                                   97

      X.  RELATIVITY                                                 107

     XI.  CAUSAL LAWS IN PHYSICS                                     114

    XII.  PHYSICS AND PERCEPTION                                     123

   XIII.  PHYSICAL AND PERCEPTUAL SPACE                              137

    XIV.  PERCEPTION AND PHYSICAL CAUSAL LAWS                        144

     XV.  THE NATURE OF OUR KNOWLEDGE OF PHYSICS                     151


  PART III

  MAN FROM WITHIN

    XVI.  SELF-OBSERVATION                                           161

   XVII.  IMAGES                                                     176

  XVIII.  IMAGINATION AND MEMORY                                     187

    XIX.  THE INTROSPECTIVE ANALYSIS OF PERCEPTION                   201

     XX.  CONSCIOUSNESS?                                             210

    XXI.  EMOTION, DESIRE, AND WILL                                  218

   XXII.  ETHICS                                                     225


  PART IV

  THE UNIVERSE

  XXIII.  SOME GREAT PHILOSOPHIES OF THE PAST                        236

   XXIV.  TRUTH AND FALSEHOOD                                        254

    XXV.  THE VALIDITY OF INFERENCE                                  266

   XXVI.  EVENTS, MATTER, AND MIND                                   276

  XXVII.  MAN’S PLACE IN THE UNIVERSE                                292




PHILOSOPHY




CHAPTER I

PHILOSOPHIC DOUBTS


Perhaps it might be expected that I should begin with a definition
of “philosophy”, but, rightly or wrongly, I do not propose to do so.
The definition of “philosophy” will vary according to the philosophy
we adopt; all that we can say to begin with is that there are certain
problems, which certain people find interesting, and which do not, at
least at present, belong to any of the special sciences. These problems
are all such as to raise doubts concerning what commonly passes for
knowledge; and if the doubts are to be answered, it can only be by
means of a special study, to which we give the name “philosophy”.
Therefore the first step in defining “philosophy” is the indication of
these problems and doubts, which is also the first step in the actual
study of philosophy. There are some among the traditional problems of
philosophy that do not seem to me to lend themselves to intellectual
treatment, because they transcend our cognitive powers; such problems I
shall not deal with. There are others, however, as to which, even if a
final solution is not possible at present, yet much can be done to show
the direction in which a solution is to be sought, and the _kind_ of
solution that may in time prove possible.

Philosophy arises from an unusually obstinate attempt to arrive at real
knowledge. What passes for knowledge in ordinary life suffers from
three defects: it is cocksure, vague, and self-contradictory. The first
step towards philosophy consists in becoming aware of these defects,
not in order to rest content with a lazy scepticism, but in order to
substitute an amended kind of knowledge which shall be tentative,
precise, and self-consistent. There is of course another quality
which we wish our knowledge to possess, namely comprehensiveness: we
wish the area of our knowledge to be as wide as possible. But this
is the business of science rather than of philosophy. A man does
not necessarily become a better philosopher through knowing more
scientific facts; it is principles and methods and general conceptions
that he should learn from science if philosophy is what interests
him. The philosopher’s work is, so to speak, at the second remove
from crude fact. Science tries to collect facts into bundles by means
of scientific laws; these laws, rather than the original facts, are
the raw material of philosophy. Philosophy involves a criticism of
scientific knowledge, not from a point of view ultimately different
from that of science, but from a point of view less concerned with
details and more concerned with the harmony of the whole body of
special sciences.

The special sciences have all grown up by the use of notions derived
from common sense, such as things and their qualities, space, time, and
causation. Science itself has shown that none of these common-sense
notions will quite serve for the explanation of the world; but it
is hardly the province of any special science to undertake the
necessary reconstruction of fundamentals. This must be the business
of philosophy. I want to say, to begin with, that I believe it to be
a business of very great importance. I believe that the philosophical
errors in common-sense beliefs not only produce confusion in science,
but also do harm in ethics and politics, in social institutions, and
in the conduct of everyday life. It will be no part of my business, in
this volume, to point out these practical effects of a bad philosophy:
my business will be purely intellectual. But if I am right, the
intellectual adventures which lie before us have effects in many
directions which seem, at first sight, quite remote from our theme. The
effect of our passions upon our beliefs forms a favourite subject of
modern psychologists; but the converse effect, that of our beliefs upon
our passions, also exists, though it is not such as an old-fashioned
intellectualist psychology would have supposed. Although I shall not
discuss it, we shall do well to bear it in mind, in order to realise
that our discussions may have bearings upon matters lying outside the
sphere of pure intellect.

I mentioned a moment ago three defects in common beliefs, namely, that
they are cocksure, vague, and self-contradictory. It is the business of
philosophy to correct these defects so far as it can, without throwing
over knowledge altogether. To be a good philosopher, a man must have a
strong desire to know, combined with great caution in believing that
he knows; he must also have logical acumen and the habit of exact
thinking. All these, of course, are a matter of degree. Vagueness,
in particular, belongs, in some degree, to all human thinking; we
can diminish it indefinitely, but we can never abolish it wholly.
Philosophy, accordingly, is a continuing activity, not something
in which we can achieve final perfection once for all. In this
respect, philosophy has suffered from its association with theology.
Theological dogmas are fixed, and are regarded by the orthodox as
incapable of improvement. Philosophers have too often tried to produce
similarly final systems: they have not been content with the gradual
approximations that satisfied men of science. In this they seem to me
to have been mistaken. Philosophy should be piecemeal and provisional
like science; final truth belongs to heaven, not to this world.

The three defects which I have mentioned are interconnected, and by
becoming aware of any one we may be led to recognise the other two. I
will illustrate all three by a few examples.

Let us take first the belief in common objects, such as tables and
chairs and trees. We all feel quite sure about these in ordinary
life, and yet our reasons for confidence are really very inadequate.
Naive common sense supposes that they are what they appear to be, but
that is impossible, since they do not appear exactly alike to any two
simultaneous observers; at least, it is impossible if the object is
a single thing, the same for all observers. If we are going to admit
that the object is not what we see, we can no longer feel the same
assurance that there is an object; this is the first intrusion of
doubt. However, we shall speedily recover from this set-back, and say
that of course the object is “really” what physics says it is.[1] Now
physics says that a table or a chair is “really” an incredibly vast
system of electrons and protons in rapid motion, with empty space in
between. This is all very well. But the physicist, like the ordinary
man, is dependent upon his senses for the existence of the physical
world. If you go up to him solemnly and say, “would you be so kind as
to tell me, as a physicist, what a chair really is”, you will get a
learned answer. But if you say, without preamble: “Is there a chair
there?” he will say: “Of course there is; can’t you see it?” To this
you ought to reply in the negative. You ought to say, “No, I see
certain patches of colour, but I don’t see any electrons or protons,
and you tell me that they are what a chair consists of”. He may reply:
“Yes, but a large number of electrons and protons close together look
like a patch of colour”. What do you mean by “look like”? you will
then ask. He is ready with an answer. He means that light-waves start
from the electrons and protons (or, more probably, are reflected by
them from a source of light), reach the eye, have a series of effects
upon the rods and cones, the optic nerve, and the brain, and finally
produce a sensation. But he has never seen an eye or an optic nerve or
a brain, any more than he has seen a chair; he has only seen patches of
colour which, he says, are what eyes “look like.” That is to say, he
thinks that the sensation you have when (as you think) you see a chair,
has a series of causes, physical and psychological, but all of them,
on his own showing, lie essentially and forever outside experience.
Nevertheless, he pretends to base his science upon observation.
Obviously there is here a problem for the logician, a problem belonging
not to physics, but to quite another kind of study. This is a first
example of the way in which the pursuit of precision destroys certainty.

      [1] I am not thinking here of the elementary physics to be
          found in a school text-book; I am thinking of modern
          theoretical physics, more particularly as regards the
          structure of atoms, as to which I shall have more to say
          in later chapters.

The physicist believes that he infers his electrons and protons from
what he perceives. But the inference is never clearly set forth in
a logical chain, and, if it were, it might not look sufficiently
plausible to warrant much confidence. In actual fact, the whole
development from common-sense objects to electrons and protons has
been governed by certain beliefs, seldom conscious, but existing in
every natural man. These beliefs are not unalterable, but they grow
and develop like a tree. We start by thinking that a chair is as it
appears to be, and is still there when we are not looking. But we find,
by a little reflection, that these two beliefs are incompatible. If
the chair is to persist independently of being seen by us, it must
be something other than the patch of colour we see, because this is
found to depend upon conditions extraneous to the chair, such as how
the light falls, whether we are wearing blue spectacles, and so on.
This forces the man of science to regard the “real” chair as the cause
(or an indispensable part of the cause) of our sensations when we see
the chair. Thus we are committed to causation as an _a priori_ belief
without which we should have no reason for supposing that there is a
“real” chair at all. Also, for the sake of permanence we bring in the
notion of substance: the “real” chair is a substance, or collection of
substances, possessed of permanence and the power to cause sensations.
This metaphysical belief has operated, more or less unconsciously, in
the inference from sensations to electrons and protons. The philosopher
must drag such beliefs into the light of day, and see whether they
still survive. Often it will be found that they die on exposure.

Let us now take up another point. The evidence for a physical law, or
for any scientific law, always involves both memory and testimony. We
have to rely both upon what we remember to have observed on former
occasions, and on what others say they have observed. In the very
beginnings of science, it may have been possible sometimes to dispense
with testimony; but very soon every scientific investigation began
to be built upon previously ascertained results, and thus to depend
upon what others had recorded. In fact, without the corroboration of
testimony we should hardly have had much confidence in the existence
of physical objects. Sometimes people suffer from hallucinations, that
is to say, they think they perceive physical objects, but are not
confirmed in this belief by the testimony of others. In such cases,
we decide that they are mistaken. It is the similarity between the
perceptions of different people in similar situations that makes us
feel confident of the external causation of our perceptions; but for
this, whatever naive beliefs we might have had in physical objects
would have been dissipated long ago. Thus memory and testimony are
essential to science. Nevertheless, each of these is open to criticism
by the sceptic. Even if we succeed, more or less, in meeting his
criticism, we shall, if we are rational, be left with a less complete
confidence in our original beliefs than we had before. Once more, we
shall become less cocksure as we become more accurate.

Both memory and testimony lead us into the sphere of psychology. I
shall not at this stage discuss either beyond the point at which it is
clear that there are genuine philosophical problems to be solved. I
shall begin with memory.

Memory is a word which has a variety of meanings. The kind that I am
concerned with at the moment is the recollection of past occurrences.
This is so notoriously fallible that every experimenter makes a record
of the result of his experiment at the earliest possible moment: he
considers the inference from written words to past events less likely
to be mistaken than the direct beliefs which constitute memory. But
some time, though perhaps only a few seconds, must elapse between
the observation and the making of the record, unless the record is
so fragmentary that memory is needed to interpret it. Thus we do not
escape from the need of trusting memory to some degree. Moreover,
without memory we should not think of interpreting records as applying
to the past, because we should not know that there was any past. Now,
apart from arguments as to the proved fallibility of memory, there is
one awkward consideration which the sceptic may urge. Remembering,
which occurs now, cannot possibly--he may say--prove that what is
remembered occurred at some other time, because the world might have
sprung into being five minutes ago, exactly as it then was, full of
acts of remembering which were entirely misleading. Opponents of
Darwin, such as Edmund Gosse’s father, urged a very similar argument
against evolution. The world, they said, was created in 4004 B.C.,
complete with fossils, which were inserted to try our faith. The world
was created suddenly, but was made such as it would have been if it
had evolved. There is no logical impossibility about this view. And
similarly there is no logical impossibility in the view that the world
was created five minutes ago, complete with memories and records. This
may seem an improbable hypothesis, but it is not logically refutable.

Apart from this argument, which may be thought fantastic, there are
reasons of detail for being more or less distrustful of memory. It
is obvious that no _direct_ confirmation of a belief about a past
occurrence is possible, because we cannot make the past recur. We can
find confirmation of an indirect kind in the revelations of others and
in contemporary records. The latter, as we have seen, involve some
degree of memory, but they may involve very little, for instance when
a shorthand report of a conversation or speech has been made at the
time. But even then, we do not escape wholly from the need of memory
extending over a longer stretch of time. Suppose a wholly imaginary
conversation were produced for some criminal purpose, we should depend
upon the memories of witnesses to establish its fictitious character in
a law-court. And all memory which extends over a long period of time is
very apt to be mistaken; this is shown by the errors invariably found
in autobiographies. Any man who comes across letters which he wrote
many years ago can verify the manner in which his memory has falsified
past events. For these reasons, the fact that we cannot free ourselves
from dependence upon memory in building up knowledge is, _prima facie_,
a reason for regarding what passes for knowledge as not quite certain.
The whole of this subject of memory will be considered more carefully
in later chapters.

Testimony raises even more awkward problems. What makes them so awkward
is the fact that testimony is involved in building up our knowledge
of physics, and that, conversely, physics is required in establishing
the trustworthiness of testimony. Moreover, testimony raises all the
problems connected with the relation of mind and matter. Some eminent
philosophers, _e.g._ Leibniz, have constructed systems according to
which there would be no such thing as testimony, and yet have accepted
as true many things which cannot be known without it. I do not think
philosophy has quite done justice to this problem, but a few words
will, I think, show its gravity.

For our purposes, we may define testimony as noises heard, or shapes
seen, analogous to those which we should make if we wished to convey
an assertion, and believed by the hearer or seer to be due to someone
else’s desire to convey an assertion. Let us take a concrete instance:
I ask a policeman the way, and he says, “Fourth turn to the right,
third to the left.” That is to say, I hear these sounds, and perhaps I
see what I interpret as his lips moving. I assume that he has a mind
more or less like my own, and has uttered these sounds with the same
intention as I should have had if I had uttered them, namely to convey
information. In ordinary life, all this is not, in any proper sense,
an inference; it is a belief which arises in us on the appropriate
occasion. But if we are challenged, we have to substitute inference for
spontaneous belief, and the more the inference is examined the more
shaky it looks.

The inference that has to be made has two steps, one physical and one
psychological. The physical inference is of the sort we considered a
moment ago, in which we pass from a sensation to a physical occurrence.
We hear noises, and think they proceed from the policeman’s body. We
see moving shapes, and interpret them as physical motions of his
lips. This inference, as we saw earlier, is in part justified by
testimony; yet now we find that it has to be made before we can have
reason to believe that there is any such thing as testimony. And this
inference is certainly sometimes mistaken. Lunatics hear voices which
other people do not hear; instead of crediting them with abnormally
acute hearing, we lock them up. But if we sometimes hear sentences
which have not proceeded from a body, why should this not always be
the case? Perhaps our imagination has conjured up all the things that
we think others have said to us. But this is part of the general
problem of inferring physical objects from sensations, which, difficult
as it is, is not the most difficult part of the logical puzzles
concerning testimony. The most difficult part is the inference from
the policeman’s body to his mind. I do not mean any special insult to
policemen; I would say the same of politicians and even of philosophers.

The inference to the policeman’s mind certainly _may_ be wrong. It is
clear that a maker of wax-works could make a life-like policeman and
put a gramophone inside him, which would cause him periodically to
tell visitors the way to the most interesting part of the exhibition
at the entrance to which he would stand. They would have just the sort
of evidence of his being alive that is found convincing in the case of
other policemen. Descartes believed that animals have no minds, but are
merely complicated automata. Eighteenth-century materialists extended
this doctrine to men. But I am not now concerned with materialism; my
problem is a different one. Even a materialist must admit that, when he
talks, he means to convey something, that is to say, he uses words as
signs, not as mere noises. It may be difficult to decide exactly what
is meant by this statement, but it is clear that it means something,
and that it is true of one’s own remarks. The question is: Are we sure
that it is true of the remarks we hear, as well as of those we make?
Or are the remarks we hear perhaps just like other noises, merely
meaningless disturbances of the air? The chief argument against this
is analogy: the remarks we hear are so like those we make that we think
they must have similar causes. But although we cannot dispense with
analogy as a form of inference, it is by no means demonstrative, and
not infrequently leads us astray. We are therefore left, once more,
with a _prima facie_ reason for uncertainty and doubt.

This question of what we mean ourselves when we speak brings me to
another problem, that of introspection. Many philosophers have held
that introspection gave the most indubitable of all knowledge; others
have held that there is no such thing as introspection. Descartes,
after trying to doubt everything, arrived at “I think, therefore I
am”, as a basis for the rest of knowledge. Dr. John B. Watson the
behaviourist holds, on the contrary, that we do not think, but only
talk. Dr. Watson, in real life, gives as much evidence of thinking as
anyone does, so if _he_ is not convinced that he thinks, we are all
in a bad way. At any rate, the mere existence of such an opinion as
his, on the part of a competent philosopher, must suffice to show that
introspection is not so certain as some people have thought. But let us
examine this question a little more closely.

The difference between introspection and what we call perception of
external objects seems to me to be connected, not with what is primary
in our knowledge, but with what is inferred. We think, at one time,
that we are seeing a chair; at another, that we are thinking about
philosophy. The first we call perception of an external object; the
second we call introspection. Now we have already found reason to doubt
external perception, in the full-blooded sense in which common-sense
accepts it. I shall consider later what there is that is indubitable
and primitive in perception; for the moment, I shall anticipate by
saying that what is indubitable in “seeing a chair” is the occurrence
of a certain pattern of colours. But this occurrence, we shall find,
is connected with me just as much as with the chair; no one except
myself can see exactly the pattern that I see. There is thus something
subjective and private about what we take to be external perception,
but this is concealed by precarious extensions into the physical world.
I think introspection, on the contrary, involves precarious extensions
into the mental world: shorn of these, it is not very different from
external perception shorn of its extensions. To make this clear, I
shall try to show what we know to be occurring when, as we say, we
think about philosophy.

Suppose, as the result of introspection, you arrive at a belief which
you express in the words: “I am now believing that mind is different
from matter”. What do you know, apart from inferences, in such a case?
First of all, you must cut out the word “I”: the person who believes
is an inference, not part of what you know immediately. In the second
place, you must be careful about the word “believing”: I am not now
concerned with what this word should mean in logic or theory of
knowledge; I am concerned with what it can mean when used to describe
a direct experience. In such a case, it would seem that it can only
describe a certain kind of feeling. And as for the proposition you
think you are believing, namely, “mind is different from matter”,
it is very difficult to say what is really occurring when you think
you believe it. It may be mere words, pronounced, visualised, or in
auditory or motor images. It may be images of what the words “mean”,
but in that case it will not be at all an accurate representation of
the logical content of the proposition. You may have an image of a
statue of Newton “voyaging through strange seas of thought alone”, and
another image of a stone rolling downhill, combined with the words “how
different!” Or you may think of the difference between composing a
lecture and eating your dinner. It is only when you come to expressing
your thought in words that you approach logical precision.

Both in introspection and in external perception, we try to express
what we know in WORDS.

We come here, as in the question of testimony, upon the social aspect
of knowledge. The purpose of words is to give the same kind of
publicity to thought as is claimed for physical objects. A number of
people can hear a spoken word or see a written word, because each is a
physical occurrence. If I say to you, “mind is different from matter”,
there may be only a very slight resemblance between the thought that I
am trying to express and the thought which is aroused in you, but these
two thoughts have just this in common, that they can be expressed by
the same words. Similarly, there may be great differences between what
you and I see when, as we say, we look at the same chair; nevertheless
we can both express our perceptions by the same words.

A thought and a perception are thus not so very different in their own
nature. If physics is true, they are different in their correlations:
when I see a chair, others have more or less similar perceptions, and
it is thought that these are all connected with light-waves coming from
the chair, whereas, when I think a thought, others may not be thinking
anything similar. But this applies also to feeling a toothache, which
would not usually be regarded as a case of introspection. On the whole,
therefore, there seems no reason to regard introspection as a different
_kind_ of knowledge from external perception. But this whole question
will concern us again at a later stage.

As for the _trustworthiness_ of introspection, there is again a
complete parallelism with the case of external perception. The actual
datum, in each case, is unimpeachable, but the extensions which we make
instinctively are questionable. Instead of saying, “I am believing
that mind is different from matter”, you ought to say, “certain images
are occurring in a certain relation to each other, accompanied by a
certain feeling”. No words exist for describing the actual occurrence
in all its particularity; all words, even proper names, are general,
with the possible exception of “this”, which is ambiguous. When you
translate the occurrence into words, you are making generalisations and
inferences, just as you are when you say “there is a chair”. There is
really no vital difference between the two cases. In each case, what is
really a datum is unutterable, and what can be put into words involves
inferences which may be mistaken.

When I say that “inferences” are involved, I am saying something not
quite accurate unless carefully interpreted. In “seeing a chair”,
for instance, we do not first apprehend a coloured pattern, and then
proceed to infer a chair: belief in the chair arises spontaneously
when we see the coloured pattern. But this belief has causes not only
in the present physical stimulus, but also partly in past experience,
partly in reflexes. In animals, reflexes play a very large part; in
human beings, experience is more important. The infant learns slowly to
correlate touch and sight, and to expect others to see what he sees.
The habits which are thus formed are essential to our adult notion
of an object such as a chair. The perception of a chair by means of
sight has a physical stimulus which affects only sight directly, but
stimulates ideas of solidity and so on through early experience. The
inference might be called “physiological”. An inference of this sort is
evidence of past correlations, for instance between touch and sight,
but may be mistaken in the present instance; you may, for instance,
mistake a reflection in a large mirror for another room. Similarly in
dreams we make mistaken physiological inferences. We cannot therefore
feel certainty in regard to things which are in this sense inferred,
because, when we try to accept as many of them as possible, we are
nevertheless compelled to reject some for the sake of self-consistency.

We arrived a moment ago at what we called “physiological inference”
as an essential ingredient in the common-sense notion of a physical
object. Physiological inference, in its simplest form, means this:
given a stimulus S, to which, by a reflex, we react by a bodily
movement R, and a stimulus S′ with a reaction R′, if the two stimuli
are frequently experienced together, S will in time produce R′.[2]
That is to say, the body will act as if S′ were present. Physiological
inference is important in theory of knowledge, and I shall have much
to say about it at a later stage. For the present, I have mentioned it
partly to prevent it from being confused with logical inference, and
partly in order to introduce the problem of _induction_, about which we
must say a few preliminary words at this stage.

      [2] _E.g._ if you hear a sharp noise and see a bright light
          simultaneously often, in time the noise without the light
          will cause your pupils to contract.

Induction raises perhaps the most difficult problem in the whole theory
of knowledge. Every scientific law is established by its means, and yet
it is difficult to see why we should believe it to be a valid logical
process. Induction, in its bare essence, consists of the argument that,
because A and B have been often found together and never found apart,
therefore, when A is found again, B will probably also be found. This
exists first as a “physiological inference”, and as such is practised
by animals. When we first begin to reflect, we find ourselves making
inductions in the physiological sense, for instance, expecting the
food we see to have a certain kind of taste. Often we only become
aware of this expectation through having it disappointed, for instance
if we take salt thinking it is sugar. When mankind took to science,
they tried to formulate logical principles justifying this kind of
inference. I shall discuss these attempts in later chapters; for the
present, I will only say that they seem to me very unsuccessful. I
am convinced that induction must have validity of some kind in some
degree, but the problem of showing how or why it can be valid remains
unsolved. Until it is solved, the rational man will doubt whether his
food will nourish him, and whether the sun will rise tomorrow. I am not
a rational man in this sense, but for the moment I shall pretend to be.
And even if we cannot be completely rational, we should probably all
be the better for becoming somewhat more rational than we are. At the
lowest estimate, it will be an interesting adventure to see whither
reason will lead us.

The problems we have been raising are none of them new, but they
suffice to show that our everyday views of the world and of our
relations to it are unsatisfactory. We have been asking whether we
know this or that, but we have not yet asked what “knowing” is. Perhaps
we shall find that we have had wrong ideas as to knowing, and that our
difficulties grow less when we have more correct ideas on this point. I
think we shall do well to begin our philosophical journey by an attempt
to understand knowing considered as part of the relation of man to his
environment, forgetting, for the moment, the fundamental doubts with
which we have been concerned. Perhaps modern science may enable us to
see philosophical problems in a new light. In that hope, let us examine
the relation of man to his environment with a view to arriving at a
scientific view as to what constitutes knowledge.




PART I

MAN FROM WITHOUT




CHAPTER II

MAN AND HIS ENVIRONMENT


If our scientific knowledge were full and complete, we should
understand ourselves and the world and our relation to the world. As
it is, our understanding of all three is fragmentary. For the present,
it is the third question, that of our relation to the world, that I
wish to consider, because this brings us nearest to the problems of
philosophy. We shall find that it will lead us back to the other two
questions, as to the world and as to ourselves, but that we shall
understand both these better if we have considered first how the world
acts upon us and how we act upon the world.

There are a number of sciences which deal with Man. We may deal with
him in natural history, as one among the animals, having a certain
place in evolution, and related to other animals in ascertainable
ways. We may deal with him in physiology, as a structure capable of
performing certain functions, and reacting to the environment in ways
of which some, at least, can be explained by chemistry. We may study
him in sociology, as a unit in various organisms, such as the family
and the state. And we may study him, in psychology, as he appears to
himself. This last gives what we may call an internal view of man, as
opposed to the other three, which give an external view. That is to
say, in psychology we use data which can only be obtained when the
observer and the observed are the same person, whereas in the other
ways of studying Man all our data can be obtained by observing other
people. There are different ways of interpreting this distinction,
and different views of its importance, but there can be no doubt
that there is such a distinction. We can remember our own dreams,
whereas we cannot know the dreams of others unless they tell us about
them. We know when we have toothache, when our food tastes too salty,
when we are remembering some past occurrence, and so on. All these
events in our lives other people cannot know in the same direct way.
In this sense, we all have an inner life, open to our own inspection
but to no one else’s. This is no doubt the source of the traditional
distinction of mind and body: the body was supposed to be that part of
us which others could observe, and the mind that part which was private
to ourselves. The importance of the distinction has been called in
question in recent times, and I do not myself believe that it has any
fundamental philosophical significance. But historically it has played
a dominant part in determining the conceptions from which men set out
when they began to philosophise, and on this account, if on no other,
it deserves to be borne in mind.

Knowledge, traditionally, has been viewed from within, as something
which we observe in ourselves rather than as something which we can see
others displaying. When I say that it has been so viewed, I mean that
this has been the practice of philosophers; in ordinary life, people
have been more objective. In ordinary life, knowledge is something
which can be tested by examinations, that is to say, it consists in a
certain kind of response to a certain kind of stimulus. This objective
way of viewing knowledge is, to my mind, much more fruitful than the
way which has been customary in philosophy. I mean that, if we wish
to give a definition of “knowing”, we ought to define it as a manner
of reacting to the environment, not as involving something (a “state
of mind”) which only the person who has the knowledge can observe.
It is because I hold this view that I think it best to begin with
Man and his environment, rather than with those matters in which the
observer and the observed must be the same person. Knowing, as I view
it, is a characteristic which may be displayed in our reactions to our
environment; it is therefore necessary first of all to consider the
nature of these reactions as they appear in science.

Let us take some everyday situation. Suppose you are watching a race,
and at the appropriate moment you say, “they’re off”. This exclamation
is a reaction to the environment, and is taken to show knowledge if it
is made at the same time as others make it. Now let us consider what
has been really happening, according to science. The complication of
what has happened is almost incredible. It may conveniently be divided
into four stages: first, what happened in the outside world between the
runners and your eyes; secondly, what happened in your body from your
eyes to your brain; thirdly, what happened in your brain; fourthly,
what happened in your body from your brain to the movements of your
throat and tongue which constituted your exclamation. Of these four
stages, the first belongs to physics, and is dealt with in the main
by the theory of light; the second and fourth belong to physiology;
the third, though it should theoretically also belong to physiology,
belongs in fact rather to psychology, owing to our lack of knowledge
as to the brain. The third stage embodies the results of experience
and learning. It is responsible for the fact that you speak, which an
animal would not do, and that you speak English, which a Frenchman
would not do. This immensely complicated occurrence is, nevertheless,
about the simplest example of knowledge that could possibly be given.

For the moment, let us leave on one side the part of this process which
happens in the outside world and belongs to physics. I shall have much
to say about it later, but what has to be said is not altogether easy,
and we will take less abstruse matters first. I will merely observe
that the event which we are said to perceive, namely the runners
starting, is separated by a longer or shorter chain of events from the
event which happens at the surface of our eyes. It is this last that
is what is called the “stimulus”. Thus the event that we are said to
perceive when we see is not the stimulus, but an anterior event related
to it in a way that requires investigation. The same applies to hearing
and smell, but not to touch or to perception of states of our own
body. In these cases, the first of the above four stages is absent.
It is clear that, in the case of sight, hearing and smell, there must
be a certain relation between the stimulus and the event said to be
perceived, but we will not now consider what this relation must be. We
will consider, rather, the second, third, and fourth stages in an act
of perceptive knowledge. This is the more legitimate as these stages
always exist, whereas the first is confined to certain senses.

The second stage is that which proceeds from the sense-organ to the
brain. It is not necessary for our purposes to consider exactly
what goes on during this journey. A purely physical event--the
stimulus--happens at the boundary of the body, and has a series
of effects which travel along the afferent nerves to the brain.
If the stimulus is light, it must fall on the eye to produce the
characteristic effects; no doubt light falling on other parts of the
body has effects, but they are not those that distinguish vision.
Similarly, if the stimulus is sound, it must fall on the ear. A
sense-organ, like a photographic plate, is responsive to stimuli
of a certain sort: light falling on the eye has effects which are
different for different wave-lengths, intensities, and directions. When
the events in the eye due to incident light have taken place, they
are followed by events in the optic nerve, leading at last to some
occurrence in the brain--an occurrence which varies with the stimulus.
The occurrence in the brain must be different for different stimuli
in all cases where we can _perceive_ differences. Red and yellow, for
instance, are distinguishable in perception; therefore the occurrences
along the optic nerve and in the brain must have a different character
when caused by red light from what they have when caused by yellow
light. But when two shades of colour are so similar that they can only
be distinguished by delicate instruments, not by perception, we cannot
be sure that they cause occurrences of different characters in the
optic nerve and brain.

When the disturbance has reached the brain, it may or may not cause a
characteristic set of events in the brain. If it does not, we shall
not be what is called “conscious” of it. For to be “conscious” of
seeing yellow, whatever else it may be, must certainly involve some
kind of cerebral reaction to the message brought by the optic nerve.
It may be assumed that the great majority of messages brought to the
brain by the afferent nerves never secure any attention at all--they
are like letters to a government office which remain unanswered. The
things in the margin of the field of vision, unless they are in some
way interesting, are usually unnoticed; if they are noticed, they
are brought into the centre of the field of vision unless we make a
deliberate effort to prevent this from occurring. These things are
visible, in the sense that we could be aware of them if we chose,
without any change in our physical environment or in our sense-organs;
that is to say, only a cerebral change is required to enable them to
cause a reaction. But usually they do not provoke any reaction; life
would be altogether too wearing if we had to be always reacting to
everything in the field of vision. Where there is no reaction, the
second stage completes the process, and the third and fourth stages do
not arise. In that case, there has been nothing that could be called
“perception” connected with the stimulus in question.

To us, however, the interesting case is that in which the process
continues. In this case there is first a process in the brain, of
which the nature is as yet conjectural, which travels from the centre
appropriate to the sense in question to a motor centre. From these
there is a process which travels along an efferent nerve, and finally
results in a muscular event causing some bodily movement. In our
illustration of the man watching the beginning of a race, a process
travels from the part of the brain concerned with sight to the part
concerned with speech; this is what we called the third stage. Then
a process travels along the efferent nerves and brings about the
movements which constitute saying “they’re off”; this is what we called
the fourth stage.

Unless all four stages exist, there is nothing that can be called
“knowledge”. And even when they are all present, various further
conditions must be satisfied if there is to be “knowledge”. But these
observations are premature, and we must return to the analysis of our
third and fourth stages.

The third stage is of two sorts, according as we are concerned with
a reflex or with a “learned reaction”, as Dr. Watson calls it. In
the case of a reflex, if it is complete at birth, a new-born infant
or animal has a brain so constituted that, without the need of any
previous experience, there is a connection between a certain process in
the afferent nerves and a certain other process in the efferent nerves.
A good example of a reflex is sneezing. A certain kind of tickling in
the nose produces a fairly violent movement having a very definite
character, and this connection exists already in the youngest infants.
Learned reactions, on the other hand, are such as only occur because of
the effect of previous occurrences in the brain. One might illustrate
by an analogy which, however, would be misleading if pressed. Imagine
a desert in which no rain has ever fallen, and suppose that at last
a thunderstorm occurs in it; then the course taken by the water will
correspond to a reflex. But if rain continues to fall frequently, it
will form watercourses and river valleys; when this has occurred, the
water runs away along pre-formed channels, which are attributable to
the past “experience” of the region. This corresponds to “learned
reactions”. One of the most notable examples of learned reactions
is speech: we speak because we have learned a certain language, not
because our brain had originally any tendency to react in just that
way. Perhaps all knowledge, certainly nearly all, is dependent upon
learned reactions, _i.e._, upon connections in the brain which are not
part of man’s congenital equipment but are the result of events which
have happened to him.

To distinguish between learned and unlearned responses is not always an
easy task. It cannot be assumed that responses which are absent during
the first weeks of life are all learned. To take the most obvious
instance; sexual responses change their character to a greater or less
extent at puberty, as a result of changes in the ductless glands, not
as a result of experience. But this instance does not stand alone:
as the body grows and develops, new modes of response come into play,
modified, no doubt, by experience, but not wholly due to it. For
example: a new-born baby cannot run, and therefore does not run away
from what is terrifying, as an older child does. The older child has
learned to run, but has not necessarily learned to run _away_; the
stimulus in learning to run may have never been a terrifying object. It
would therefore be a fallacy to suppose that we can distinguish between
learned and unlearned responses by observing what a new-born infant
does, since reflexes may come into play at a later stage. Conversely,
some things which a child does at birth may have been learned, when
they are such as it could have done in the womb--for example, a certain
amount of kicking and stretching. The whole distinction between learned
and unlearned responses, therefore, is not so definite as we could
wish. At the two extremes we get clear cases, such as sneezing on the
one hand and speaking on the other; but there are intermediate forms of
behaviour which are more difficult to classify.

This is not denied even by those who attach most importance to the
distinction between learned and unlearned responses. In Dr. Watson’s
_Behaviorism_ (p. 103) there is a “Summary of Unlearned Equipment”,
which ends with the following paragraph:

“Other activities appear at a later stage--such as blinking, reaching,
handling, handedness, crawling, standing, sitting-up, walking, running,
jumping. _In the great majority of these later activities it is
difficult to say how much of the act as a whole is due to training
or conditioning. A considerable part is unquestionably due to the
growth changes in structure, and the remainder is due to training and
conditioning._” (Watson’s italics.)

It is not possible to make a logically sharp distinction in this
matter; in certain cases we have to be satisfied with something less
exact. For example, we might say that those developments which are
merely due to normal growth are to count as unlearned, while those
which depend upon special circumstances in the individual biography are
to count as learned. But take, say, muscular development: this will
not take place normally unless the muscles are used, and if they are
used they are bound to learn some of the skill which is appropriate to
them. And some things which must certainly count as learned, such as
focussing with the eyes, depend upon circumstances which are normal
and must be present in the case of every child who is not blind. The
whole distinction, therefore, is one of degree rather than of kind;
nevertheless it is valuable.

The value of the distinction between learned and unlearned reactions
is connected with the laws of learning, to which we shall come in the
next chapter. Experience modifies behaviour according to certain laws,
and we may say that a learned reaction is one in the formation of which
these laws have played a part. For example: children are frightened of
loud noises from birth, but are not at first frightened of dogs; after
they have heard a dog barking loudly, they may become frightened of
dogs, which is a learned reaction. If we knew enough about the brain,
we could make the distinction precise, by saying that learned reactions
are those depending upon modifications of the brain other than mere
growth. But as it is, we have to judge by observations of bodily
behaviour, and the accompanying modifications in the brain are assumed
on a basis of theory rather than actually observed.

The essential points, for our purposes, are comparatively simple.
Man or any other animal, at birth, is such as to respond to certain
stimuli in certain specific ways, _i.e._ by certain kinds of bodily
movements; as he grows, these ways of responding change, partly as the
mere result of developing structure, partly in consequence of events in
his biography. The latter influence proceeds according to certain laws,
which we shall consider, since they have much to do with the genesis of
“knowledge”.

But--the indignant reader may be exclaiming--knowing something is not
a bodily movement, but a state of mind, and yet you talk to us about
sneezing and such matters. I must ask the indignant reader’s patience.
He “knows” that he has states of mind, and that his knowing is itself
a state of mind. I do not deny that he has states of mind, but I ask
two questions: First, what sort of thing are they? Secondly, what
evidence can he give me that he knows about them? The first question
he may find very difficult; and if he wants, in his answer, to show
that states of mind are something of a sort totally different from
bodily movements, he will have to tell me also what bodily movements
are, which will plunge him into the most abstruse part of physics. All
this I propose to consider later on, and then I hope the indignant
reader will be appeased. As to the second question, namely, what
evidence of his knowledge another man can give me, it is clear that he
must depend upon speech or writing, _i.e._ in either case upon bodily
movements. Therefore whatever knowledge may be to the knower, as a
social phenomenon it is something displayed in bodily movements. For
the present I am deliberately postponing the question of what knowledge
is to the knower, and confining myself to what it is for the external
observer. And for him, necessarily, it is something shown by bodily
movements made in answer to stimuli--more specifically, to examination
questions. What else it may be I shall consider at a later stage.

However we may subsequently add to our present account by considering
how knowledge appears to the knower, that will not invalidate anything
that we may arrive at by considering how knowledge appears to the
external observer. And there is something which it is important
to realise, namely, that we are concerned with a process in which
the environment first acts upon a man, and then he reacts upon the
environment. This process has to be considered as a whole if we are
to discuss what knowledge is. The older view would have been that the
effect of the environment upon us might constitute a certain kind
of knowledge (perception), while our reaction to the environment
constituted volition. These were, in each case, “mental” occurrences,
and their connection with nerves and brain remained entirely
mysterious. I think the mystery can be eliminated, and the subject
removed from the realm of guesswork, by starting with the whole
cycle from stimulus to bodily movement. In this way, knowing becomes
something active, not something contemplative. Knowing and willing, in
fact, are merely aspects of the one cycle, which must be considered in
its entirety if it is to be rightly understood.

A few words must be said about the human body as a mechanism. It is
an inconceivably complicated mechanism, and some men of science think
that it is not explicable in terms of physics and chemistry, but is
regulated by some “vital principle” which makes its laws different
from those of dead matter. These men are called “vitalists”. I do not
myself see any reason to accept their view, but at the same time our
knowledge is not sufficient to enable us to reject it definitely. What
we can say is that their case is not proved, and that the opposite view
is, scientifically, a more fruitful working hypothesis. It is better
to look for physical and chemical explanations where we can, since
we know of many processes in the human body which can be accounted
for in this way, and of none which _certainly_ cannot. To invoke a
“vital principle” is to give an excuse for laziness, when perhaps more
diligent research would have enabled us to do without it. I shall
therefore assume, as a working hypothesis, that the human body acts
according to the same laws of physics and chemistry as those which
govern dead matter, and that it differs from dead matter, not by its
laws, but by the extraordinary complexity of its structure.

The movements of the human body may, none the less, be divided into two
classes, which we may call respectively “mechanical” and “vital”. As
an example of the former, I should give the movement of a man falling
from a cliff into the sea. To explain this, in its broad features, it
is not necessary to take account of the fact that the man is alive; his
centre of gravity moves exactly as that of a stone would move. But when
a man climbs up a cliff, he does something that dead matter of the
same shape and weight would never do; this is a “vital” movement. There
is in the human body a lot of stored chemical energy in more or less
unstable equilibrium; a very small stimulus can release this energy,
and cause a considerable amount of bodily movement. The situation is
analogous to that of a large rock delicately balanced on the top of a
conical mountain; a tiny shove may send it thundering down into the
valley, in one direction or another according to the direction of the
shove. So if you say to a man “your house is on fire”, he will start
running; although the stimulus contained very little energy, his
expenditure of energy may be tremendous. He increases the available
energy by panting, which makes his body burn up faster and increases
the energy due to combustion; this is just like opening the draft in a
furnace. “Vital” movements are those that use up this energy which is
in unstable equilibrium. It is they alone that concern the bio-chemist,
the physiologist, and the psychologist. The others, being just like
the movements of dead matter, may be ignored when we are specially
concerned with the study of Man.

Vital movements have a stimulus which may be inside or outside the
body, or both at once. Hunger is a stimulus inside the body, but
hunger combined with the sight of good food is a double stimulus, both
internal and external. The effect of a stimulus may be, in theory,
according to the laws of physics and chemistry, but in most cases
this is, at present, no more than a pious opinion. What we know from
observation is that behaviour is modified by experience, that is to
say, that if similar stimuli are repeated at intervals they produce
gradually changing reactions. When a bus conductor says, “Fares,
please”, a very young child has no reaction, an older child gradually
learns to look for pennies, and, if a male, ultimately acquires the
power of producing the requisite sum on demand without conscious
effort. The way in which our reactions change with experience is a
distinctive characteristic of animals; moreover it is more marked in
the higher than in the lower animals, and most marked of all in Man.
It is a matter intimately connected with “intelligence”, and must be
investigated before we can understand what constitutes knowledge from
the standpoint of the external observer; we shall be concerned with it
at length in the next chapter.

Speaking broadly, the actions of all living things are such as tend to
biological survival, _i.e._ to the leaving of a numerous progeny. But
when we descend to the lowest organisms, which have hardly anything
that can be called individuality, and reproduce themselves by fission,
it is possible to take a simpler view. Living matter, within limits,
has the chemical peculiarity of being self-perpetuating, and of
conferring its own chemical composition upon other matter composed of
the right elements. One spore falling into a stagnant pond may produce
millions of minute vegetable organisms; these, in turn, enable one
small animal to have myriads of descendants living on the small plants;
these, in turn, provide life for larger animals, newts, tadpoles,
fishes, etc. In the end there is enormously more protoplasm in that
region than there was to begin with. This is no doubt explicable as a
result of the chemical constitution of living matter. But this purely
chemical self-preservation and collective growth is at the bottom of
everything else that characterises the behaviour of living things.
Every living thing is a sort of imperialist, seeking to transform as
much as possible of its environment into itself and its seed. The
distinction between self and posterity is one which does not exist in
a developed form in asexual unicellular organisms; many things, even
in human life, can only be completely understood by forgetting it.
We may regard the whole of evolution as flowing from this “chemical
imperialism” of living matter. Of this, Man is only the last example
(so far). He transforms the surface of the globe by irrigation,
cultivation, mining, quarrying, making canals and railways, breeding
certain animals, and destroying others; and when we ask ourselves,
from the standpoint of an outside observer, what is the end achieved
by all these activities, we find that it can be summed up in one
very simple formula: to transform as much as possible of the matter
on the earth’s surface into human bodies. Domestication of animals,
agriculture, commerce, industrialism have been stages in this process.
When we compare the human population of the globe with that of
other large animals and also with that of former times, we see that
“chemical imperialism” has been, in fact, the main end to which human
intelligence has been devoted. Perhaps intelligence is reaching the
point where it can conceive worthier ends, concerned with the quality
rather than the quantity of human life. But as yet such intelligence
is confined to minorities, and does not control the great movements of
human affairs. Whether this will ever be changed I do not venture to
predict. And in pursuing the simple purpose of maximising the amount of
human life, we have at any rate the consolation of feeling at one with
the whole movement of living things from their earliest origin on this
planet.




CHAPTER III

THE PROCESS OF LEARNING IN ANIMALS AND INFANTS


In the present chapter I wish to consider the processes by which,
and the laws according to which, an animal’s original repertoire of
reflexes is changed into a quite different set of habits as a result
of events that happen to it. A dog learns to follow his master in
preference to anyone else; a horse learns to know his own stall in
the stable; a cow learns to come to the cow-shed at milking time.
All these are acquired habits, not reflexes; they depend upon the
circumstances of the animals concerned, not merely upon the congenital
characteristics of the species. When I speak of an animal “learning”
something, I shall include all cases of acquired habits, whether or not
they are useful to the animal. I have known horses in Italy “learn” to
drink wine, which I cannot believe to have been a desirable habit. A
dog may “learn” to fly at a man who has ill-treated it, and may do so
with such regularity and ferocity as to lead to its being killed. I do
not use learning in any sense involving praise, but merely to denote
modification of behaviour as the result of experience.

The manner in which animals learn has been much studied in recent
years, with a great deal of patient observation and experiment. Certain
results have been obtained as regards the kinds of problems that have
been investigated, but on general principles there is still much
controversy. One may say broadly that all the animals that have been
carefully observed have behaved so as to confirm the philosophy in
which the observer believed before his observations began. Nay, more,
they have all displayed the national characteristics of the observer.
Animals studied by Americans rush about frantically, with an incredible
display of hustle and pep, and at last achieve the desired result by
chance. Animals observed by Germans sit still and think, and at last
evolve the solution out of their inner consciousness. To the plain
man, such as the present writer, this situation is discouraging. I
observe, however, that the type of problem which a man naturally sets
to an animal depends upon his own philosophy, and that this probably
accounts for the differences in the results. The animal responds to
one type of problem in one way and to another in another; therefore
the results obtained by different investigators, though different, are
not incompatible. But it remains necessary to remember that no one
investigator is to be trusted to give a survey of the whole field.

The matters with which we shall be concerned in this chapter belong to
behaviourist psychology, and in part to pure physiology. Nevertheless,
they seem to me vital to a proper understanding of philosophy, since
they are necessary for an objective study of knowledge and inference. I
mean by an “objective” study one in which the observer and the observed
need not be the same person; when they must be identical, I call the
study “subjective.” For the present we are concerned with what is
required for understanding “knowledge” as an objective phenomenon. We
shall take up the question of the subjective study of knowledge at a
later stage.

The scientific study of learning in animals is a very recent growth;
it may almost be regarded as beginning with Thorndike’s _Animal
Intelligence_, which was published in 1911. Thorndike invented the
method which has been adopted by practically all subsequent American
investigators. In this method an animal is separated from food, which
he can see or smell, by an obstacle which he may overcome by chance. A
cat, say, is put in a cage having a door with a handle which he may by
chance push open with his nose. At first the cat makes entirely random
movements, until he gets his result by a mere fluke. On the second
occasion, in the same cage, he still makes some random movements, but
not so many as on the first occasion. On the third occasion he does
still better, and before long he makes no useless movements. Nowadays
it has become customary to employ rats instead of cats, and to put them
in a model of the Hampton Court maze rather than in a cage. They take
all sorts of wrong turnings at first, but after a time they learn to
run straight out without making any mistake. Dr. Watson gives averages
for nineteen rats, each of which was put into the maze repeatedly,
with food outside where the rat could smell it. In all the experiments
care was taken to make sure that the animal was very hungry. Dr.
Watson says: “The first trial required on the average over seventeen
minutes. During this time the rat was running around the maze, into
blind alleys, running back to the starting point, starting for the food
again, biting at the wires around him, scratching himself, smelling
this spot and that on the floor. Finally he got to the food. He was
allowed only a bite. Again he was put back into the maze. The taste of
the food made him almost frantic in his activity. He dashed about more
rapidly. The average time for the group on the second trial is only a
little over seven minutes; on the fourth trial not quite three minutes;
from this point to the twenty-third trial the improvement is very
gradual.” On the thirtieth trial the time required, on the average,
was about thirty seconds.[3] This set of experiments may be taken as
typical of the whole group of studies to which it belongs.

      [3] Watson, _Behaviorism_, pp. 169–70.

Thorndike, as a result of experiments with cages and mazes, formulated
two “provisional laws,” which are as follows:

“The Law of Effect is that: of several responses made to the same
situation, those which are accompanied or closely followed by
satisfaction to the animal will, other things being equal, be more
firmly connected with the situation, so that, when it recurs, they
will be more likely to recur; those which are accompanied or closely
followed by dissatisfaction to the animal will, other things being
equal, have their connections with that situation weakened, so that,
when it recurs, they will be less likely to recur. The greater the
satisfaction or discomfort, the greater the strengthening or weakening
of the bond.

“The Law of Exercise is that: Any response to a situation will, other
things being equal, be more strongly connected with the situation in
proportion to the number of times it has been connected with that
situation and to the average vigour and duration of the connections.”

We may sum up these two laws, roughly, in the two statements: First, an
animal tends to repeat what has brought it pleasure; second, an animal
tends to repeat what it has often done before. Neither of these laws is
at all surprising, but, as we shall see, there are difficulties in the
theory that they are adequate to account for the process of learning in
animals.

Before going further there is a theoretical point to be cleared up.
Thorndike, in his first law, speaks of satisfaction and discomfort,
which are terms belonging to subjective psychology. We cannot observe
whether an animal _feels_ satisfaction or _feels_ discomfort; we can
only observe that it behaves in ways that we have become accustomed to
interpret as signs of these feelings. Thorndike’s law, as it stands,
does not belong to objective psychology, and is not capable of being
experimentally tested. This, however, is not so serious an objection
as it looks. Instead of speaking of a result that brings satisfaction,
we can merely enumerate the results which, in fact, have the character
which Thorndike mentions, namely, that the animal tends to behave so
as to make them recur. The rat in the maze behaves so as to get the
cheese, and when an act has led him to the cheese once, he tends to
repeat it. We may say that this is what we mean when we say that the
cheese “gives satisfaction”, or that the rat “desires” the cheese.
That is to say, we may use Thorndike’s “Law of Effect” to give us an
objective definition of desire, satisfaction, and discomfort. The law
should then say: there are situations such that animals tend to repeat
acts which have led to them; these are the situations which the animal
is said to “desire” and in which it is said to “find satisfaction”.
This objection to Thorndike’s first law is, therefore, not very
serious, and need not further trouble us.

Dr. Watson considers one principle alone sufficient to account for
all animal and human learning, namely, the principle of “learned
reactions.” This principle may be stated as follows:

_When the body of an animal or human being has been exposed
sufficiently often to two roughly simultaneous stimuli, the earlier of
them alone tends to call out the response previously called out by the
other._

Although I do not agree with Dr. Watson in thinking this principle
alone sufficient, I do agree that it is a principle of very great
importance. It is the modern form of the principle of “association”.
The “association of ideas” has played a great part in philosophy,
particularly in British philosophy. But it now appears that this is
a consequence of a wider and more primitive principle, namely, the
association of bodily processes. It is this wider principle that is
asserted above. Let us see what is the nature of the evidence in its
favour.

Our principle becomes verifiable over a much larger field than the
older principle owing to the fact that it is movements, not “ideas”,
that are to be associated. Where animals are concerned, ideas are
hypothetical, but movements can be observed; even with men, many
movements are involuntary and unconscious. Yet animal movements and
unconscious involuntary human movements are just as much subject to
the law of association as the most conscious ideas. Take, _e.g._ the
following example (Watson, p. 33). The pupil of the eye expands in
darkness and contracts in bright light; this is an involuntary and
unconscious action of which we only become aware by observing others.
Now take some person and repeatedly expose him to bright light at
the same moment that you ring an electric bell. After a time the
electric bell alone will cause his pupils to contract. As far as can be
discovered, all muscles behave in this way. So do glands where they can
be tested. It is said that a brass band can be reduced to silence by
sucking a lemon in front of it, owing to the effect upon the salivary
glands of its members; I confess that I have never verified this
statement. But you will find the exact scientific analogue for dogs in
Watson, p. 26. You arrange a tube in a dog’s mouth so that saliva drops
out at a measurable rate. When you give the dog food it stimulates the
flow of saliva. At the same moment you touch his left thigh. After a
certain length of time the touch on the left thigh will produce just
as much saliva without the food as with it. The same sort of thing
applies to emotions, which depend upon the ductless glands. Children
at birth are afraid of loud noises, but not of animals. Watson took a
child eleven months old, who was fond of a certain white rat; twice at
the moment when the child touched the rat, a sudden noise was made just
behind the child’s head. This was enough to cause fear of the rat on
subsequent occasions, no doubt owing to the fact that the adrenal gland
was now stimulated by the substitute stimulus, just like the salivary
glands in the dog or the trumpet player. The above illustrations show
that “ideas” are not the essential units in association. It seems that
not merely is “mind” irrelevant, but even the brain is less important
than was formerly supposed. At any rate, what is known experimentally
is that the glands and muscles (both striped and unstriped) of the
higher animals exhibit the law of transfer of response, _i.e._ when
two stimuli have often been applied together, one will ultimately call
out the response which formerly the other called out. This law is one
of the chief bases of habit. It is also obviously essential to our
understanding of language: the sight of a dog calls up the word “dog”,
and the word “dog” calls up some of the responses appropriate to a real
dog.

There is, however, another element in learning, besides mere habit.
This is the element dealt with by Thorndike’s “Law of Effect.” Animals
tend to repeat acts which have pleasant consequences, and to avoid
such as have unpleasant consequences. But, as we saw a moment ago,
“pleasant” and “unpleasant” are words which we cannot verify by
objective observation. What we can verify by observation is that
an animal seeks situations which in fact have had certain results,
and avoids situations which in fact have had certain other results.
Moreover, broadly speaking, the animal seeks results which tend to
survival of itself or its offspring, and avoids results which tend in
the opposite direction. This, however, is not invariable. Moths seek
flames and men seek drink, though neither is biologically useful. It
is only approximately, in situations long common, that animals are so
adjusted to their environment as to act in a way which is advantageous
from a biological standpoint. In fact, biological utility must
never be employed as an explanation, but only noticed as a frequent
characteristic, of the ways in which animals behave.

Dr. Watson is of the opinion that Thorndike’s “Law of Effect” is
unnecessary. He first suggests that only two factors are called for in
the explanation of habit, namely, _frequency_ and _recency_. Frequency
is covered by Thorndike’s “Law of Exercise”, but recency, which is
almost certainly a genuine factor, is not covered by Thorndike’s two
laws. That is to say, when a number of random movements have finally
resulted in success, the more recent of these movements are likely to
be repeated earlier, on a second trial, than the earlier ones. But Dr.
Watson finally abandons this method of dealing with habit-formation in
favour of the one law of “conditioned reflexes” or “learned reactions”.
He says (_Behaviorism_, p. 166):

“Only a few psychologists have been interested in the problem. Most
of the psychologists, it is to be regretted, have even failed to see
that there is a problem. They believe habit formation is implanted by
kind fairies. For example, Thorndike speaks of pleasure stamping in
the successful movement and displeasure stamping out the unsuccessful
movements. Most of the psychologists talk, too, quite volubly about the
formation of new pathways in the brain, as though there were a group
of tiny servants of Vulcan there who run through the nervous system
with hammer and chisel digging new trenches and deepening old ones.
I am not sure that the problem when phrased in this way is a soluble
one. I feel that there must come some simpler way of envisaging the
whole process of habit formation or else it may remain insoluble.
Since the advent of the conditioned reflex hypothesis in psychology
with all of the simplifications (and I am often fearful that it may be
an oversimplification!) I have had my own laryngeal processes [_i.e._
what others call “thoughts”] stimulated to work upon this problem from
another angle.”

I agree with Dr. Watson that the explanations of habit-formation which
are usually given are very inadequate, and that few psychologists have
realised either the importance or the difficulty of the problem. I
agree also that a great many cases are covered by his formula of the
conditioned reflex. He relates a case of a child who once touched a
hot radiator, and afterward avoided it for two years. He adds: “If we
should keep our old habit terminology, we should have in this example
a habit formed by a single trial. There can be then in this case no
‘stamping in of the successful movement’ and ‘no stamping out of the
unsuccessful movement.’” On the basis of such examples, he believes
that the whole of habit-formation can be derived from the principle of
the conditioned reflex, which he formulates as follows (p. 168):

_Stimulus X will not now call out reaction R; stimulus Y will call out
reaction R (unconditioned reflex); but when stimulus X is presented
first and then Y (which does call out R) shortly thereafter, X will
thereafter call out R. In other words, stimulus X becomes ever
thereafter substituted for Y._

This law is so simple, so important, and so widely true that there
is a danger lest its scope should be exaggerated, just as, in the
eighteenth century, physicists tried to explain everything by means of
gravitation. But when considered as covering all the ground, it seems
to me to suffer from two opposite defects. In the first place, there
are cases where no habit is set up, although by the law it should be.
In the second place, there are habits which, so far as we can see at
present, have a different genesis.

To take the first point first: the word “pepper” does not make people
sneeze, though according to the law it should.[4] Words which describe
succulent foods will make the mouth water; voluptuous words will have
some of the effect that would be produced by the situations they
suggest; but no words will produce sneezes or the reactions appropriate
to tickling. In the diagram given by Dr. Watson (p. 106), there are
four reflexes which appear to be not sources of conditioned reflexes,
namely sneezing, hiccoughing, blinking, and the Babinski reflex;
of these, however, blinking, it is suggested (p. 99) may be really
itself a conditioned reflex. There may be some quite straightforward
explanation of the fact that some reactions can be produced by
substitute stimuli while others cannot, but none is offered. Therefore
the law of the conditioned reflex, as formulated, is too wide, and it
is not clear what is the principle according to which its scope should
be restricted.

      [4] Dr. Watson apparently entertains hopes of teaching babies
          to sneeze when they see the pepper box, but he has not
          yet done so. See _Behaviorism_, p. 90.

The second objection to Dr. Watson’s law of habit, if valid, is more
important than the first; but its validity is more open to question. It
is contended that the acts by which solutions of problems are obtained
are, in cases of a certain kind, not random acts leading to success by
mere chance, but acts proceeding from “insight”, involving a “mental”
solution of the problem as a preliminary to the physical solution.
This is especially the view of those who advocate _Gestaltpsychologie_
or the psychology of configuration. We may take, as typical of their
attitude on the subject of learning, Köhler’s _Mentality of Apes_.
Köhler went to Tenerife with certain chimpanzees in the year 1913;
owing to the war he was compelled to remain with them until 1917, so
that his opportunities for study were extensive. He complains of the
maze and cage problems set by American investigators that they are such
as _cannot_ be solved by intelligence. Sir Isaac Newton himself could
not have got out of the Hampton Court maze by any method except trial
and error. Köhler, on the other hand, set his apes problems which could
be solved by what he calls “insight”. He would hang up a banana[5] out
of reach, and leave boxes in the neighbourhood so that by standing
on the boxes the chimpanzees could reach the fruit. Sometimes they
had to pile three or even four boxes on top of each other before they
could achieve success. Then he would put the banana outside the bars
of the cage, leaving a stick inside, and the ape would get the banana
by reaching for it with the stick. On one occasion, one of them, named
Sultan, had two bamboo sticks, each too short to reach the banana;
after vain efforts followed by a period of silent thought, he fitted
the smaller into the hollow of the other, and so manufactured one stick
which was long enough. It seems, however, from the account, that he
first fitted the two together more or less accidentally, and only then
realised that he had found a solution. Nevertheless, his behaviour when
he had once realised that one stick could be made by joining the two
was scarcely Watsonian: there was no longer anything tentative, but a
definite triumph, first in anticipation and then in action. He was so
pleased with his new trick that he drew a number of bananas into his
cage before eating any of them. He behaved, in fact, as capitalists
have behaved with machinery.

      [5] Called by Köhler “the objective,” because the word
          “banana” is too humble for a learned work. The pictures
          disclose the fact that “the objective” was a mere banana.

Köhler says: “We can, from our own experience, distinguish sharply
between the kind of conduct which, from the very beginning, arises out
of a consideration of the characteristics of a situation, and one that
does not. Only in the former case do we speak of insight, and only
that behaviour of animals definitely appears to us intelligent which
takes account from the beginning of the lie of the land, and proceeds
to deal with it in a smooth continuous course. Hence follows this
characteristic: _to set up as the criterion of insight, the appearance
of a complete solution with reference to the whole lay-out of the
field_.”

Genuine solutions of problems, Köhler says, do not improve by
repetition; they are perfect on the first occasion, and, if anything,
grow worse by repetition, when the excitement of discovery has worn
off. The whole account that Köhler gives of the efforts of his
chimpanzees makes a totally different impression from that of the
rats in mazes, and one is forced to conclude that the American work
is somewhat vitiated by confining itself to one type of problem,
and drawing from that one type conclusions which it believes to be
applicable to all problems of animal learning. It seems that there
are two ways of learning, one by experience, and the other by what
Köhler calls “insight”. Learning by experience is possible to most
vertebrates, though rarely, so far as is known, to invertebrates.
Learning by “insight”, on the contrary, is not known to exist in any
animals lower than the anthropoid apes, though it would be extremely
rash to assert that it will not be revealed by further observations on
dogs or rats. Unfortunately, some animals--for instance, elephants--may
be extremely intelligent, but the practical difficulty and expense of
experimentation with them is so great that we are not likely to know
much about them for some time to come. However, the real problem is
already sufficiently definite in Köhler’s book: it is the analysis of
“insight” as opposed to the method of the conditioned reflex.

Let us first be clear as to the nature of the problem, when described
solely in terms of behaviour. A hungry monkey, if sufficiently near
to a banana, will perform acts such as, in circumstances to which it
has been accustomed, have previously enabled it to obtain bananas.
This fits well with either Watson or Thorndike, so far. But if these
familiar acts fail, the animal will, if it has been long without food,
is in good health, and is not too tired, proceed to other acts which
have never hitherto produced bananas. One may suppose, if one wishes to
follow Watson, that these new acts are composed of a number of parts,
each of which, on some former occasion, has occurred in a series which
ended with the obtaining of the banana. Or one may suppose--as I think
Thorndike does--that the acts of the baffled animal are random acts,
so that the solution emerges by pure chance. But even in the first
hypothesis, the element of chance is considerable. Let us suppose that
the acts A, B, C, D, E, have each, on a former occasion, been part of
a series ending with success, but that now for the first time it is
necessary to perform them all, and in the right order. It is obvious
that, if they are only combined by chance, the animal will be lucky if
it performs them all in the right order before dying of hunger.

But Köhler maintains that to anyone watching his chimpanzees it was
obvious they did not obtain “a composition of the solution out of
chance parts”. He says (pp. 199–200):

“It is certainly not a characteristic of the chimpanzee, when he is
brought into an experimental situation, to make any chance movements,
out of which, among other things, a non-genuine solution could arise.
He is very seldom seen to attempt anything which would have to be
considered accidental in relation to the situation (excepting, of
course, if his interest is turned away from the objective to other
things). As long as his efforts are directed to the objective, all
distinguishable stages of his behaviour (as with human beings in
similar situations) tend to appear as complete attempts at solutions,
_none_ of which appears as the product of accidentally arrayed
parts. This is true, most of all, of the solution which is finally
successful. Certainly it often follows upon a period of perplexity or
quiet (often a period of survey), but in real and convincing cases,
the solution never appears in a disorder of blind impulses. It is
one continuous smooth action, which can be resolved into its parts
_only by the imagination_ of the onlooker; in reality they do _not_
appear independently. But that in so many ‘genuine’ cases as have been
described, these solutions as wholes should have arisen from mere
chance, is an entirely inadmissible supposition.”

Thus we may take it as an observed fact that, so far as overt behaviour
is concerned, there are two objections to the type of theory with
which we began, when considered as covering the whole field. The first
objection is that in cases of a certain kind, the solution appears
sooner than it should according to the doctrine of chances; the second
is that it appears as a whole, _i.e._ that the animal, after a period
of quiescence, suddenly goes through the right series of actions
smoothly, and without hesitation.

Where human beings are concerned, it is difficult to obtain such
good data as in the case of animals. Human mothers will not allow
their children to be starved, and then shut up in a room containing
a banana which can only be reached by putting a chair on the table
and a footstool on the chair, and then climbing up without breaking
any bones. Nor will they permit them to be put into the middle of a
Hampton Court maze, with their dinner getting cold outside. Perhaps
in time the State will perform these experiments with the children of
political prisoners, but as yet, perhaps fortunately, the authorities
are not sufficiently interested in science. One can observe, however,
that human learning seems to be of both sorts, namely that described
by Watson and that described by Köhler. I am persuaded that speech is
learnt by the Watsonian method, so long as it is confined to single
words: often the trial and error, in later stages, proceeds _sotto
voce_, but it takes place overtly at first, and in some children until
their speech is quite correct. The speaking of sentences, however, is
already more difficult to explain without bringing in the apprehension
of wholes which is the thing upon which _Gestaltpsychologie_
lays stress. In the later stages of learning, the sort of sudden
illumination which came to Köhler’s chimpanzees is a phenomenon with
which every serious student must be familiar. One day, after a period
of groping bewilderment, the schoolboy knows what algebra is all
about. In writing a book, my own experience--which I know is fairly
common, though by no means universal--is that for a time I fumble and
hesitate, and then suddenly I see the book as a whole, and have only
to write it down as if I were copying a completed manuscript.

If these phenomena are to be brought within the scope of behaviourist
psychology, it must be by means of “implicit” behaviour. Watson makes
much use of this in the form of talking to oneself, but in apes it
cannot take quite this form. And it is necessary to have some theory
to explain the success of “implicit” behaviour, whether we call it
“thought” or not. Perhaps such a theory can be constructed on Watson’s
lines, but it has certainly not yet been constructed. Until the
behaviourists have satisfactorily explained the kind of discovery which
appears in Köhler’s observations, we cannot say that their thesis is
proved. This is a matter which will occupy us again at a later stage;
for the present let us preserve an open mind.




CHAPTER IV

LANGUAGE


The subject of language is one which has not been studied with
sufficient care in traditional philosophy. It was taken for granted
that words exist to express “thoughts,” and generally also that
“thoughts” have “objects” which are what the words “mean”. It was
thought that, by means of language, we could deal directly with what
it “means”, and that we need not analyse with any care either of the
two supposed properties of words, namely that of “expressing” thoughts
and that of “meaning” things. Often when philosophers intended to be
considering the objects meant by words they were in fact considering
only the words, and when they were considering words they made the
mistake of supposing, more or less unconsciously, that a word is a
single entity, not, as it really is, a set of more or less similar
events. The failure to consider language explicitly has been a cause
of much that was bad in traditional philosophy. I think myself that
“meaning” can only be understood if we treat language as a bodily
habit, which is learnt just as we learn football or bicycling. The only
satisfactory way to treat language, to my mind, is to treat it in this
way, as Dr. Watson does. Indeed, I should regard the theory of language
as one of the strongest points in favour of behaviourism.

Man has various advantages over the beasts, for example, fire,
clothing, agriculture, and tools--not the possession of domestic
animals, for ants have them. But more important than any of these
is language. It is not known how or when language arose, nor why
chimpanzees do not speak. I doubt if it is even known whether writing
or speech is the older form of language. The pictures made in caves by
the Cro-Magnon men may have been intended to convey a meaning, and may
have been a form of writing. It is known that writing developed out of
pictures, for that happened in historical times; but it is not known
to what extent pictures had been used in pre-historic times as a means
of giving information or commands. As for spoken language, it differs
from the cries of animals in being not merely an expression of emotion.
Animals have cries of fear, cries expressing pleasure in the discovery
of food, and so on, and by means of these cries they influence each
other’s actions. But they do not appear to have any means of expressing
anything except emotions, and then only emotions which they are
actually feeling. There is no evidence that they possess anything
analogous to narrative. We may say, therefore, without exaggeration,
that language is a human prerogative, and probably the chief habit in
which we are superior to the “dumb” animals.

There are three matters to be considered in beginning the study of
language. First: what words are, regarded as physical occurrences;
secondly, what are the circumstances that lead us to use a given word;
thirdly, what are the effects of our hearing or seeing a given word.
But as regards the second and third of these questions, we shall find
ourselves led on from words to sentences and thus confronted with fresh
problems perhaps demanding rather the methods of _Gestaltpsychologie_.

Ordinary words are of four kinds: spoken, heard, written, and read. It
is of course largely a matter of convention that we do not use words of
other kinds. There is the deaf-and-dumb language; a Frenchman’s shrug
of the shoulders is a word; in fact, any kind of externally perceptible
bodily movement may become a word, if social usage so ordains. But the
convention which has given the supremacy to speaking is one which has
a good ground, since there is no other way of producing a number of
perceptibly different bodily movements so quickly or with so little
muscular effort. Public speaking would be very tedious if statesmen
had to use the deaf-and-dumb language, and very exhausting if all
words involved as much muscular effort as a shrug of the shoulders. I
shall ignore all forms of language except speaking, hearing, writing,
and reading, since the others are relatively unimportant and raise no
special psychological problems.

A spoken word consists of a series of movements in the larynx and
the mouth, combined with breath. Two closely similar series of such
movements may be instances of the same words, though they may also
not be, since two words with different meanings may sound alike; but
two such series which are not closely similar cannot be instances of
the same word. (I am confining myself to one language.) Thus a single
spoken word, say “dog,” is a certain set of closely similar series of
bodily movements, the set having as many members as there are occasions
when the word “dog” is pronounced. The degree of similarity required
in order that the occurrence should be an instance of the word “dog”
cannot be specified exactly. Some people say “dawg”, and this must
certainly be admitted. A German might say “tok”, and then we should
begin to be doubtful. In marginal cases, we cannot be sure whether a
word has been pronounced or not. A spoken word is a form of bodily
behaviour without sharp boundaries, like jumping or hopping or running.
Is a man running or walking? In a walking-race the umpire may have
great difficulty in deciding. Similarly there may be cases where it
cannot be decided whether a man has said “dog” or “dock”. A spoken word
is thus at once general and somewhat vague.

We usually take for granted the relation between a word spoken and a
word heard. “Can you hear what I say?” we ask, and the person addressed
says “yes”. This is of course a delusion, a part of the naive realism
of our unreflective outlook on the world. We never hear what is said;
we hear something having a complicated causal connection with what is
said. There is first the purely physical process of sound-waves from
the mouth of the speaker to the ear of the hearer, then a complicated
process in the ear and nerves, and then an event in the brain, which
is related to our hearing of the sound in a manner to be investigated
later, but is at any rate simultaneous with our hearing of the sound.
This gives the physical causal connection between the word spoken and
the word heard. There is, however, also another connection of a more
psychological sort. When a man utters a word, he also hears it himself,
and so that the word spoken and the word heard become intimately
associated for anyone who knows how to speak. And a man who knows how
to speak can also utter any word he hears in his own language, so that
the association works equally well both ways. It is because of the
intimacy of this association that the plain man identifies the word
spoken with the word heard, although in fact the two are separated by a
wide gulf.

In order that speech may serve its purpose, it is not necessary, as it
is not possible, that heard and spoken words should be identical, but
it is necessary that when a man utters different words the heard words
should be different, and when he utters the same word on two occasions
the heard word should be approximately the same on the two occasions.
The first of these depends upon the sensitiveness of the ear and its
distance from the speaker; we cannot distinguish between two rather
similar words if we are too far off from the man who utters them. The
second condition depends upon uniformity in the physical conditions,
and is realised in all ordinary circumstances. But if the speaker were
surrounded by instruments which were resonant to certain notes but not
to certain others, some tones of voice might carry and others might
be lost. In that case, if he uttered the same word with two different
intonations, the hearer might be quite unable to recognise the
sameness. Thus the efficacy of speech depends upon a number of physical
conditions. These, however, we will take for granted, in order to come
as soon as possible to the more psychological parts of our topic.

Written words differ from spoken words in being material structures. A
spoken word is a process in the physical world, having an essential
time-order; a written word is a series of pieces of matter, having
an essential space-order. As to what we mean by “matter”, that is a
question with which we shall have to deal at length at a later stage.
For the present it is enough to observe that the material structures
which constitute written words, unlike the processes that constitute
spoken words, are capable of enduring for a long time--sometimes
for thousands of years. Moreover, they are not confined to one
neighbourhood, but can be made to travel about the world. These are the
two great advantages of writing over speech. This, at least, has been
the case until recently. But with the coming of radio writing it has
begun to lose its pre-eminence: one man can now speak to multitudes
spread over a whole country. Even in the matter of permanence, speech
may become the equal of writing. Perhaps, instead of legal documents,
we shall have gramophone records, with voice signatures by the parties
to the contract. Perhaps, as in Wells’s _When the Sleeper Awakes_,
books will no longer be printed but merely arranged for the gramophone.
In that case the need for writing may almost cease to exist. However,
let us return from these speculations to the world of the present day.

The word read, as opposed to the written or printed word, is just
as evanescent as the word spoken or heard. Whenever a written word,
exposed to light, is in a suitable spatial relation to a normal eye, it
produces a certain complicated effect upon the eye; the part of this
process which occurs outside the eye is investigated by the science of
light, whereas the part that occurs in the eye belongs to physiological
optics. There is then a further process, first in the optic nerve and
afterwards in the brain; the process in the brain is simultaneous
with vision. What further relation it has to vision is a question
as to which there has been much philosophical controversy; we shall
return to it at a later stage. The essence of the matter, as regards
the causal efficacy of writing, is that the act of writing produces
quasi-permanent material structures which, throughout the whole of
their duration, produce closely similar results upon all suitably
placed normal eyes; and as in the case of speaking, different written
words lead to different read words, and the same word written twice
leads to the same read word--again with obvious limitations.

So much for the physical side of language, which is often unduly
neglected. I come now to the psychological side, which is what really
concerns us in this chapter.

The two questions we have to answer, apart from the problems raised
by sentences as opposed to words, are: First, what sort of behaviour
is stimulated by hearing a word? And secondly, what sort of occasion
stimulates us to the behaviour that consists in pronouncing a word? I
put the questions in this order because children learn to react to the
words of others before they learn to use words themselves. It might be
objected that, in the history of the race, the first spoken word must
have preceded the first heard word, at least by a fraction of a second.
But this is not very relevant, nor is it certainly true. A noise may
have meaning to the hearer, but not to the utterer; in that case it
is a heard word but not a spoken word. (I shall explain what I mean
by “meaning” shortly.) Friday’s footprint had “meaning” for Robinson
Crusoe but not for Friday. However that may be, we shall do better
to avoid the very hypothetical parts of anthropology that would be
involved, and take up the learning of language as it can be observed in
the human infant of the present day. And in the human infant as we know
him, definite reactions to the words of others come much earlier than
the power of uttering words himself.

A child learns to understand words exactly as he learns any other
process of bodily association. If you always say “bottle” when you give
a child his bottle, he presently reacts to the word “bottle”, within
limits, as he formerly reacted to the bottle. This is merely an example
of the law of association which we considered in the preceding chapter.
When the association has been established, parents say that the child
“understands” the word “bottle”, or knows what the word “means”. Of
course the word does not have _all_ the effects that the actual bottle
has. It does not exert gravitation, it does not nourish, it cannot
bump on to the child’s head. The effects which are shared by the word
and the thing are those which depend upon the law of association or
“conditional reflexes” or “learned reactions”. These may be called
“associative” effects or “mnemic” effects--the latter name being
derived from Semon’s book _Mneme_,[6] in which he traces all phenomena
analogous to memory to a law which is, in effect, not very different
from the law of association or “conditioned reflexes”.

      [6] London: George Allen & Unwin, Ltd.

It is possible to be a little more precise as to the class of effects
concerned. A physical object is a centre from which a variety of
causal chains emanate. If the object is visible to John Smith, one
of the causal chains emanating from it consists first of light-waves
(or light-quanta) which travel from the object to John Smith’s eye,
then of events in his eye and optic nerve, then of events in his
brain, and then (perhaps) of a reaction on his part. Now mnemic
effects belong only to events in living tissue; therefore only those
effects of the bottle which happen either inside John Smith’s body,
or as a result of his reaction to the bottle, can become associated
with his hearing the word “bottle”. And even then only certain events
can be associated: nourishment happens in the body, yet the word
“bottle” cannot nourish. The law of conditioned reflexes is subject
to ascertainable limitations, but within its limits it supplies what
is wanted to explain the understanding of words. The child becomes
excited when he sees the bottle; this is already a conditioned reflex,
due to experience that this sight precedes a meal. One further stage
in conditioning makes the child grow excited when he hears the word
“bottle”. He is then said to “understand” the word.

We may say, then, that a person understands a word which he hears if,
so far as the law of conditioned reflexes is applicable, the effects of
the word are the same as those of what it is said to “mean”. This of
course only applies to words like “bottle”, which denote some concrete
object or some class of concrete objects. To understand a word such
as “reciprocity” or “republicanism” is a more complicated matter, and
cannot be considered until we have dealt with sentences. But before
considering sentences we have to examine the circumstances which make
us use a word, as opposed to the consequences of hearing it used.

Saying a word is more difficult than using it, except in the case of
a few simple sounds which infants make before they know that they are
words, such as “ma-ma” and “da-da.” These two are among the many random
sounds that all babies make. When a child says “ma-ma” in the presence
of his mother by chance she thinks he knows what this noise means, and
she shows pleasure in ways that are agreeable to the infant. Gradually,
in accordance with Thorndike’s law of effect, he acquires the habit
of making this noise in the presence of his mother, because in these
circumstances the consequences are pleasant. But it is only a very
small number of words that are acquired in this way. The great majority
of words are acquired by imitation, combined with the association
between thing and word which the parents deliberately establish in the
early stages (after the very first stage). It is obvious that using
words oneself involves something over and above the association between
the _sound_ of the word and its meaning. Dogs understand many words,
and infants understand far more than they can say. The infant has to
discover that it is possible and profitable to make noises like those
which he hears. (This statement must not be taken quite literally, or
it would be too intellectualistic.) He would never discover this if
he did not make noises at random, without the intention of talking.
He then gradually finds that he can make noises like those which he
hears, and in general the consequences of doing so are pleasant.
Parents are pleased, desired objects can be obtained, and--perhaps most
important of all--there is a sense of power in making intended instead
of accidental noises. But in this whole process there is nothing
essentially different from the learning of mazes by rats. It resembles
this form of learning, rather than that of Köhler apes, because no
amount of intelligence could enable the child to find out the names of
things--as in the case of the mazes, experience is the only possible
guide.

When a person knows how to speak, the conditioning proceeds in the
opposite direction to that which operates in understanding what others
say. The reaction of a person who knows how to speak, when he notices
a cat, is naturally to utter the word “cat”; he may not actually do
so, but he will have a reaction leading towards this act, even if for
some reason the overt act does not take place. It is true that he may
utter the word “cat” because he is “thinking” about a cat, not actually
seeing one. This, however, as we shall see in a moment, is merely one
further stage in the process of conditioning. The use of single words,
as opposed to sentences, is wholly explicable, so far as I can see, by
the principles which apply to animals in mazes.

Certain philosophers who have a prejudice against analysis contend that
the sentence comes first and the single word later. In this connection
they always allude to the language of the Patagonians, which their
opponents, of course, do not know. We are given to understand that a
Patagonian can understand you if you say “I am going to fish in the
lake behind the western hill”, but that he cannot understand the word
“fish” by itself. (This instance is imaginary, but it represents the
sort of thing that is asserted.) Now it may be that Patagonians are
peculiar--indeed they must be, or they would not choose to live in
Patagonia. But certainly infants in civilized countries do not behave
in this way, with the exception of Thomas Carlyle and Lord Macaulay.
The former never spoke before the age of three, when, hearing his
younger brother cry, he said, “What ails wee Jock?” Lord Macaulay
“learned in suffering what he taught in song”, for, having spilt a cup
of hot tea over himself at a party, he began his career as a talker
by saying to his hostess, after a time, “Thank you, Madam, the agony
is abated”. These, however, are facts about biographers, not about
the beginnings of speech in infancy. In all children that have been
carefully observed, sentences come much later than single words.

Children, at first, are limited as to their power of producing sounds,
and also by the paucity of their learned associations. I am sure the
reason why “ma-ma” and “da-da” have the meaning they have is that they
are sounds which infants make spontaneously at an early age, and are
therefore convenient as sounds to which the elders can attach meaning.
In the very beginning of speech there is not imitation of grownups, but
the discovery that sounds made spontaneously have agreeable results.
Imitation comes later, after the child has discovered that sounds
can have this quality of “meaning”. The type of skill involved is
throughout exactly similar to that involved in learning to play a game
or ride a bicycle.

We may sum up this theory of meaning in a simple formula. When through
the law of conditioned reflexes, A has come to be a cause of C, we will
call A an “associative” cause of C, and C an “associative” effect of
A. We shall say that, to a given person, the word A, when he hears it,
“means” C, if the associative effects of A are closely similar to those
of C; and we shall say that the word A, when he utters it, “means” C,
if the utterance of A is an associative effect of C, or of something
previously associated with C. To put the matter more concretely, the
word “Peter” means a certain person if the associated effects of
hearing the word “Peter” are closely similar to those of seeing Peter,
and the associative causes of uttering the word “Peter” are occurrences
previously associated with Peter. Of course as our experience increases
in complexity this simple schema becomes obscured and overlaid, but I
think it remains fundamentally true.

There is an interesting and valuable book by Messrs. C. K. Ogden and
I. A. Richards, called _The Meaning of Meaning_. This book, owing to
the fact that it concentrates on the causes of uttering words, not on
the effects of hearing them, gives only half the above theory, and that
in a somewhat incomplete form. It says that a word and its meaning have
the same causes. I should distinguish between _active_ meaning, that
of the man uttering the word, and _passive_ meaning, that of the man
hearing the word. In active meaning the word is associatively caused by
what it means or something associated with this; in passive meaning,
the associative effects of the word are approximately the same as those
of what it means.

On behaviourist lines, there is no important difference between proper
names and what are called “abstract” or “generic” words. A child learns
to use the word “cat”, which is general, just as he learns to use
the word “Peter”, which is a proper name. But in actual fact “Peter”
really covers a number of different occurrences, and is in a sense
general. Peter may be near or far, walking or standing or sitting,
laughing or frowning. All these produce different stimuli, but the
stimuli have enough in common to produce the reaction consisting
of the word “Peter”. Thus there is no essential difference, from a
behaviourist point of view, between “Peter” and “man”. There are
more resemblances between the various stimuli to the word “Peter”
than between those to the word “man”, but this is only a difference
of degree. We have not names for the fleeting particular occurrences
which make up the several appearances of Peter, because they are not
of much practical importance; their importance, in fact, is purely
theoretic and philosophical. As such, we shall have a good deal to say
about them at a later stage. For the present, we notice that there are
many occurrences of Peter, and many occurrences of the word “Peter”;
each, to the man who sees Peter, is a set of events having certain
similarities. More exactly, the occurrences of Peter are _causally_
connected, whereas the occurrences of the word “Peter” are connected by
similarity. But this is a distinction which need not concern us yet.

General words such as “man” or “cat” or “triangle” are said to denote
“universals”, concerning which, from the time of Plato to the present
day, philosophers have never ceased to debate. Whether there are
universals, and, if so, in what sense, is a metaphysical question,
which need not be raised in connection with the use of language. The
only point about universals that needs to be raised at this point is
that the correct use of general words is no evidence that a man can
think about universals. It has often been supposed that, because we can
use a word like “man” correctly, we must be capable of a corresponding
“abstract” idea of man, but this is quite a mistake. Some reactions
are appropriate to one man, some to another, but all have certain
elements in common. If the word “man” produces in us the reactions
which are common but no others, we may be said to understand the
word “man”. In learning geometry, one acquires the habit of avoiding
special interpretations of such a word as “triangle”. We know that,
when we have a proposition about triangles in general, we must not
think specially of a right-angled triangle or any one kind of triangle.
This is essentially the process of learning to associate with the word
what is associated with _all_ triangles; when we have learnt this,
we understand the word “triangle”. Consequently there is no need to
suppose that we ever apprehend universals, although we use general
words correctly.

Hitherto we have spoken of single words, and among these we have
considered only those that can naturally be employed singly. A child
uses single words of a certain kind before constructing sentences; but
some words presuppose sentences. No one would use the word “paternity”
until after using such sentences as “John is the father of James”; no
one would use the word “causality” until after using such sentences as
“the fire makes me warm”. Sentences introduce new considerations, and
are not quite so easily explained on behaviourist lines. Philosophy,
however, imperatively demands an understanding of sentences, and we
must therefore consider them.

As we found earlier, all infants outside Patagonia begin with single
words, and only achieve sentences later. But they differ enormously in
the speed with which they advance from the one to the other. My own two
children adopted entirely different methods. My son first practised
single letters, then single words, and only achieved correct sentences
of more than three or four words at the age of two and three months.
My daughter, on the contrary, advanced very quickly to sentences, in
which there was hardly ever an error. At the age of eighteen months,
when supposed to be sleeping, she was overheard saying to herself:
“Last year I used to dive off the diving-board, I _did_.” Of course
“last year” was merely a phrase repeated without understanding. And
no doubt the first sentences used by children are always repetitions,
unchanged, of sentences they have heard used by others. Such cases
raise no new principle not involved in the learning of words. What does
raise a new principle is the power of putting together known words into
a sentence which has never been heard, but which expresses correctly
what the infant wishes to convey. This involves the power to manipulate
form and structure. It does not of course involve the apprehension
of form or structure in the abstract, any more than the use of the
word “man” involves apprehension of a universal. But it does involve
a causal connection between the form of the stimulus and the form of
the reaction. An infant very soon learns to be differently affected by
the statement “cats eat mice” from the way he would be affected by the
statement “mice eat cats”; and not much later he learns to make one of
these statements rather than the other. In such a case, the cause (in
hearing) or the effect (in speaking) is a whole sentence. It may be
that one part of the environment is sufficient to cause one word, while
another is sufficient to cause another, but it is only the two parts
in their relation that can cause the whole sentence. Thus wherever
sentences come in we have a causal relation between two complex facts,
namely the fact asserted and the sentence asserting it; the facts
as wholes enter into the cause-and-effect relation, which cannot be
explained wholly as compounded of relations between their parts.
Moreover, as soon as the child has learned to use correctly relational
words, such as “eat”, he has become capable of being causally affected
by a relational feature of the environment, which involves a new degree
of complexity not required for the use of ordinary nouns.

Thus the correct use of relational words, _i.e._ of sentences, involves
what may be correctly termed “perception of form”, _i.e._ it involves a
definite reaction to a stimulus which is a form. Suppose, for example,
that a child has learnt to say that one thing is “above” another when
this is in fact the case. The stimulus to the use of the word “above”
is a relational feature of the environment, and we may say that this
feature is “perceived” since it produces a definite reaction. It may
be said that the relation _above_ is not very like the word “above”.
That is true; but the same is true of ordinary physical objects. A
stone, according to the physicists, is not at all like what we see
when we look at it, and yet we may be correctly said to “perceive” it.
This, however, is to anticipate. The definite point which has emerged
is that, when a person can use sentences correctly, that is a proof of
sensitiveness to formal or relational stimuli.

The structure of a sentence asserting some relational fact, such as
“this is above that”, or “Brutus killed Cæsar”, differs in an important
respect from the structure of the fact which it asserts. _Above_ is
a relation which holds between the two terms “this” and “that”; but
the _word_ “above” is not a relation. In the sentence the relation is
the temporal order of the words (or the spatial order, if they are
written), but the word for the relation is itself as substantial as
the other words. In inflected languages, such as Latin, the order of
the words is not necessary to show the “sense” of the relation; but in
uninflected languages this is the only way of distinguishing between
“Brutus killed Cæsar” and “Cæsar killed Brutus”. Words are physical
phenomena, having spatial and temporal relations; we make use of these
relations in our verbal symbolisation of other relations, chiefly to
show the “sense” of the relation, _i.e._ whether it goes from A to B or
from B to A.

A great deal of the confusion about relations which has prevailed in
practically all philosophies comes from the fact, which we noticed
just now, that relations are indicated, not by other relations,
but by words which, in themselves, are just like other words.
Consequently, in thinking about relations, we constantly hover between
the unsubstantiality of the relation itself and the substantiality of
the word. Take, say, the fact that lightning precedes thunder. If we
were to express this by a language closely reproducing the structure
of the fact, we should have to say simply: “lightning, thunder”, where
the fact that the first word precedes the second means that what the
first word means precedes what the second word means. But even if we
adopted this method for temporal order, we should still need words
for all other relations, because we could not without intolerable
ambiguity symbolise them also by the order of our words. All this will
be important to remember when we come to consider the structure of the
world, since nothing but a preliminary study of language will preserve
us from being misled by language in our metaphysical speculations.

Throughout this chapter I have said nothing about the narrative and
imaginative uses of words; I have dealt with words in connection
with an immediate sensible stimulus closely connected with what they
mean. The other uses of words are difficult to discuss until we have
considered memory and imagination. In the present chapter I have
confined myself to a behaviouristic explanation of the effects of
words heard as stimuli, and the causes of words spoken when the words
apply to something sensibly present. I think we shall find that other
uses of words, such as the narrative and imaginative, involve only new
applications of the law of association. But we cannot develop this
theme until we have discussed several further psychological questions.




CHAPTER V

PERCEPTION OBJECTIVELY REGARDED


It will be remembered that the task upon which we are at present
engaged is the definition of “knowledge” as a phenomenon discoverable
by an outside observer. When we have said what we can from this
objective standpoint, we will ask ourselves whether anything further,
and if so what, is to be learnt from the subjective standpoint, in
which we take account of facts which can only be discovered when the
observer and the observed are the same person. But for the present we
will resolutely confine ourselves to those facts about a human being
which another human being can observe, together with such inferences as
can be drawn from these facts.

The word “knowledge” is very ambiguous. We say that Watson’s rats
“know” how to get out of mazes, that a child of three “knows” how to
talk, that a man “knows” the people with whom he is acquainted, that
he “knows” what he had for breakfast this morning, and that he “knows”
when Columbus first crossed the ocean. French and German are less
ambiguous, since each has two words for different kinds of “knowing”,
which we tend to confuse in our thoughts because we confuse them in our
language. I shall not attempt as yet to deal with knowledge in general,
but rather with certain less general concepts which would ordinarily
be included under “knowledge”. And first of all I will deal with
perception--not as it appears to the perceiver, but as it can be tested
by an outside observer.

Let us try, first, to get a rough preliminary view of the sort of
thing we are going to mean by “perception”. One may say that a man
“perceives” anything that he notices through his senses. This is not
a question of the sense-organs alone, though they are a necessary
condition. No man can perceive by sight what is not in his field of
vision, but he may look straight at a thing without perceiving it. I
have frequently had the experience--supposed to be characteristic of
philosophers--of looking everywhere for my spectacles although they
were before my eyes when my search began. We cannot therefore tell
what a man is perceiving by observing his sense-organs alone, though
they may enable us to know that he is _not_ perceiving something.
The observer can only know that a man is perceiving something if the
man reacts in some appropriate manner. If I say to a man “please
pass the mustard” and he thereupon passes it, it is highly probable
that he perceived what I said, although it _may_ of course be a mere
coincidence that he passed it at that moment. But if I say to him “the
telephone number you want is 2467” and he proceeds to call that number,
the odds against his doing so by mere chance are very great--roughly
10,000 to 1. And if a man reads aloud out of a book, and I look over
his shoulder and perceive the same words, it becomes quite fantastic to
suppose that he does not perceive the words he is uttering. We can thus
in many cases achieve practical certainty as to some of the things that
other people are perceiving.

Perception is a species of a wider genus, namely _sensitivity_.
Sensitivity is not confined to living things; in fact it is best
exemplified by scientific instruments. A material object is said to
be “sensitive” to such and such a stimulus, if, when the stimulus is
present, it behaves in a way noticeably different from that in which
it behaves in the absence of the stimulus. A photographic plate is
sensitive to light, a barometer is sensitive to pressure, a thermometer
to temperature, a galvanometer to electric current, and so on. In all
these cases, we might say, in a certain metaphorical sense, that an
instrument “perceives” the stimulus to which it is sensitive. We do not
in fact say so; we feel that perception involves something more than we
find in scientific instruments. What is this something more?

The traditional answer would be: consciousness. But this answer,
right or wrong, is not what we are seeking at the moment, because we
are considering the percipient as he appears to an outside observer,
to whom his “consciousness” is only an inference. Is there anything
in perception as viewed from without that distinguishes it from the
sensitivity of a scientific instrument?

There is, of course, the fact that human beings are sensitive to
a greater variety of stimuli than any instrument. Each separate
sense-organ can be surpassed by something made artificially sensitive
to its particular stimulus. Photographic plates can photograph stars
that we cannot see; clinical thermometers register differences of
temperature that we cannot feel; and so on. But there is no way of
combining a microscope, a microphone, a thermometer, a galvanometer,
and so on, into a single organism which will react in an integral
manner to the combination of all the different stimuli that affect its
different “sense-organs”. This, however, is perhaps only a proof that
our mechanical skill is not so great as it may in time become. It is
certainly not enough to define the difference between a dead instrument
and a living body.

The chief difference--perhaps the only one from our present point of
view--is that living bodies are subject to the law of association or
of the “conditioned reflex”. Consider, for instance, an automatic
machine. It has a reflex which makes it sensitive to pennies, in
response to which it gives up chocolate. But it never learns to give
up chocolate on merely seeing a penny, or hearing the word “penny”.
If you kept it in your house, and said “Abracadabra” to it every time
you inserted a penny, it would not in the end be moved to action by
the mere word “Abracadabra”. Its reflexes remain unconditioned, as
do some of ours, such as sneezing. But with us sneezing is peculiar
in this respect--hence its unimportance. Most of our reflexes can be
conditioned, and the conditioned reflex can in turn be conditioned
afresh, and so on without limit. This is what makes the reactions of
the higher animals, and especially of man, so much more interesting
and complicated than the reactions of machines. Let us see whether
this one law will suffice to distinguish perception from other forms of
sensitivity.

The variability in a human being’s responses to a given stimulus
has given rise to the traditional distinction between cognition and
volition. When one’s rich uncle comes for a visit, smiles are the
natural response; after he has lost his money, a colder demeanour
results from the new conditioning. Thus the reaction to the stimulus
has come to be divided into two parts, one purely receptive and
sensory, the other active and motor. Perception, as traditionally
conceived, is, so to speak, the end term of the receptive-sensory part
of the reaction, while volition (in its widest sense) is the first term
of the active-motor part of the reaction. It was possible to suppose
that the receptive part of the reaction would be always the same for
the same stimulus, and that the difference due to experience would
only arise in the motor part. The last term of the passive part, as it
appears to the person concerned, was called “sensation”. But in fact
the influence of the law of conditioned reflexes goes much deeper than
this theory supposed. As we saw, the contraction of the pupil, which is
normally due to bright light, can be conditioned so as to result from
a loud noise. What we see depends largely upon muscular adjustments
of the eyes, which we make quite unconsciously. But apart from the
contraction of the pupil only one of them is a true reflex, namely
turning the eyes towards a bright light. This is a movement which
children can perform on the day of their birth; I know this, not merely
from personal observation, but also, what is more, from the text-books.
But new-born infants cannot follow a moving light with their eyes, nor
can they focus or accommodate. As a consequence, the purely receptive
part of their reaction to visual objects, in so far as this reaction is
visual, is different from that of adults or older children, whose eye
muscles adjust themselves so as to see clearly.

But here again all sorts of factors enter in. Innumerable objects are
in our field of vision, but only some (at most) are interesting to us.
If some one says “look, there’s a snake”, we adjust our eyes afresh
and obtain a new “sensation”. Then, when the purely visual part is
finished, there are stimulations, by association, of other centres
in the brain. There are pictures, in Köhler’s book, of apes watching
other apes on the top of insecure piles of boxes, and the spectators
have their arms raised in sympathetic balancing movements. Any one
who watches gymnastics or skilful dancing is liable to experience
sympathetic muscular contractions. Any visual object that we might be
touching will stimulate incipient touch reactions, but the sun, moon,
and stars do not.

Conversely, visual reactions may be stimulated through association with
other stimuli. When motor-cars were still uncommon, I was walking one
day with a friend when a tire punctured in our neighbourhood with a
loud report. He thought it was a revolver, and averred that he had seen
the flash. In dreams, this sort of mechanism operates uncontrolled.
Some stimulus--say the noise of the maid knocking at the door--becomes
interpreted in fantastic ways which are governed by association. I
remember once dreaming that I was in an inn in the country in Germany
and was wakened by a choir singing outside my window. Finally I
really woke, and found that a spring shower was making a very musical
noise on the roof. At least, I heard a very musical noise, and now
re-interpreted it as a shower on the roof. This hypothesis I confirmed
by looking out of the window. In waking life we are critical of the
interpretative hypotheses that occur to us, and therefore do not make
such wild mistakes as in dreams. But the creative, as opposed to the
critical, mechanism is the same in waking life as it is in dreams:
there is always far more richness in the experience than the sensory
stimulus alone would warrant. All adaptation to environment acquired
during the life of the individual might be regarded as learning to
dream dreams that succeed rather than dreams that fail. The dreams we
have when we are asleep usually end in a surprise: the dreams we have
in waking life are less apt to do so. Sometimes they do, as when pride
goes before a fall; but in that case they are regarded as showing
maladjustment, unless there is some large external cause, such as
an earthquake. One might say that a person properly adapted to his
environment is one whose dreams never end in the sort of surprise that
would wake him up. In that case, he will think that his dreams are
objective reality. But if modern physics is to be believed, the dreams
we call waking perceptions have only a very little more resemblance to
objective reality than the fantastic dreams of sleep. They have some
truth, but only just so much as is required to make them useful.

Until we begin to reflect, we unhesitatingly assume that what we
see is really “there” in the outside world, except in such cases as
reflections in mirrors. Physics and the theory of the way in which
perceptions are caused show that this naive belief cannot be quite
true. Perception may, and I think does, enable us to know something of
the outer world, but it is not the direct revelation that we naturally
suppose it to be. We cannot go into this question adequately until we
have considered what the philosopher has to learn from physics; I am
merely giving, by anticipation, the reasons for regarding perception
as a form of reaction to the environment, displayed in some bodily
movement, rather than as a form of knowledge. When we have considered
further what constitutes knowledge, we may find that perception is,
after all, a form of knowledge, but only because knowledge is not
quite what we naturally suppose it to be. For the present, let us
stick to the view of perception that can be obtained by the external
observer, _i.e._ as something displayed in the manner of reacting to
the environment.

From the point of view of the external observer, perception is
established just like any other causal correlation. We observe that,
whenever a certain object stands in a certain spatial relation to
a man’s body, the man’s body makes a certain movement or set of
movements; we shall then say that the man “perceives” the object. So
the new-born baby turns its eyes slowly towards a bright light which
is not in the centre of the field of vision; this entitles us to say
that the baby “perceives” the light. If he is blind, his eyes do not
move in this way. A bird flying about in a wood does not bump into the
branches, whereas in a room it will bump into the glass of the window.
This entitles us to say that the bird perceives the branches but not
the glass. Do we “perceive” the glass or do we merely know that it
is there? This question introduces us to the complications produced
by association. We know by experience, from the sense of touch, that
there is usually glass in window-frames; thus it makes us react to
the window-frames as if we could see the glass. But sometimes there
is no glass, and still we shall perhaps behave as if there were. If
this can happen, it shows that we do not perceive the glass, since our
reaction is the same whether there is glass or not. If, however, the
glass is coloured, or slightly distorting, or not perfectly clean,
a person accustomed to glass will be able to distinguish a frame
containing glass from one which has none. In that case it is more
difficult to decide whether we are to say that he “perceives” the
glass or not. It is certain that perception is affected by experience.
A person who can read perceives print where another would not. A
musician perceives differences between notes which to an untrained ear
are indistinguishable. People unaccustomed to the telephone cannot
understand what they hear in it; but this is perhaps not really a case
in point.

The difficulty we are considering arises from the fact that a human
body, unlike a scientific instrument, is perpetually changing its
reaction to a given stimulus, under the influence of the law of
association. Moreover, the human body is always doing something.
How, then, are we to know whether what it is doing is the result of
a given stimulus or not? In most cases, however, this difficulty is
not very serious, particularly when we are dealing with people old
enough to speak. When you go to the oculist he asks you to read a
number of letters growing gradually smaller; at some point you fail.
Where you have succeeded, he knows that you have perceived enough to
make out what letter it is. Or you take a pair of compasses and press
the points into a man’s back, asking him if he feels two pricks or
only one. He may say one when the two points are near together; if he
is on his guard against this error he may say two when in fact there
is only one. But if the points are sufficiently far apart he will
never make a mistake. That is to say, the bodily movement consisting
in pronouncing the word “two” will invariably result from a certain
stimulus. (Invariably, I mean, for a given subject on a given day.)
This entitles us to say that the man can perceive that there are two
points provided they are not too near together. Or you say: “What can
you see on the horizon?” One man says, “I see a ship”. Another says, “I
see a steamer with two funnels”. A third says, “I see a Cunarder going
from Southampton to New York”. How much of what these three people say
is to count as perception? They may all three be perfectly right in
what they say, and yet we should not concede that a man can “perceive”
that the ship is going from Southampton to New York. This, we should
say, is inference. But it is by no means easy to draw a line; some
things which are, in an important sense, inferential, must be admitted
to be perceptions. The man who says “I see a ship” is using inference.
Apart from experience, he only sees a queerly shaped dark dot on a blue
background. Experience has taught him that that sort of dot “means” a
ship; that is to say, he has a conditioned reflex which causes him to
utter, aloud or to himself, the word “ship” when his eye is stimulated
in a certain way. To disentangle what is due to experience, and what
not, in the perceptions of an adult, is a hopeless task. Practically,
if a word comes without previous verbal intermediaries, the ordinary
man would include what the word means in the perception, while he would
not do so if the man arrives at the word after verbal preliminaries,
overt or internal. But this is itself a question of familiarity. Show
a child a pentagon, and he will have to count the sides to know how
many there are; but after a little experience of geometrical figures,
the word “pentagon” will arise without any previous words. And in any
case such a criterion is theoretically worthless. The whole affair is a
matter of degree, and we cannot draw any sharp line between perception
and inference. As soon as this is realised, our difficulties are seen
to be purely verbal and therefore unimportant.

It will be observed that we are not attempting at present to say what
constitutes perception, but only what kind of behaviour on the part
of a person whom we are observing will justify us in saying that he
has perceived this or that feature of his environment. I suggest that
we are justified in saying that a man “perceives” such a feature if,
throughout some such period as a day, there is some bodily act which
he performs whenever that feature is present, but not at any other
time. This condition is clearly sufficient, but not necessary--that
is to say, there may be perception even when it is not fulfilled. A
man’s reaction may change through conditioning, even in so short a
period as a day. Again, there may be a reaction, but one which is too
slight to be observable; in this case the criterion of perception
is theoretically satisfied, but not practically, since no one can
know that it is. We often have evidence later on that something was
perceived, although at the moment there was no discoverable reaction.
I have frequently known children repeat afterwards some remark which,
at the time, they seemed not to have heard. This sort of case affords
another kind of evidence of perception, namely, the evidence afforded
by a delayed response. Some people will sit silent and impassive in a
company of talkers, giving no evidence that they are listening; yet
they may go home and write down the conversation verbatim in their
journals. These are the typical writers of memoirs. More remarkable
still, I know one man--a man of genius, it is true--who talks
incessantly, who yet, after meeting a total stranger, knows exactly
what the stranger would have said if he had been given the chance.
How this is managed, I do not know; but such a man is rightly called
“perceptive”.

Obviously, in dealing with human beings old enough to talk, words
afford the best evidence of perception. A man’s verbal responses to
perceptive situations do not change much after the first few years of
life. If you see a kingfisher, and at the same moment your companion
says “there’s a kingfisher”, that is pretty conclusive evidence that
he saw it. But, as this case illustrates, our evidence that some one
else has perceived something always depends upon our own perceptions.
And our own perceptions are known to us in a different way from that
in which the perceptions of others are known to us. This is one of
the weak spots in the attempt at a philosophy from the objective
standpoint. Such a philosophy really assumes knowledge as a going
concern, and takes for granted the world which a man derives from
his own perceptions. We cannot tackle all our philosophical problems
by the objective method, but it is worth while to proceed with it as
far as it will take us. This whole question of perception will have
to be attacked afresh from a different angle, and we shall then find
reason to regard the behaviouristic standpoint as inadequate, though
valid so far as it goes. We have still, however, a long road to go
before we shall be driven to consider the subjective standpoint;
more particularly, we have to define “knowledge” and “inference”
behaviouristically, and then, making a new start, to consider what
modern physics makes of “matter”. But for the moment there are still
some things to be said about perception from the objective standpoint.

It will be seen that, according to our criterion of perception, an
object perceived need not be in contact with the percipient’s body. The
sun, moon, and stars are perceived according to the above criterion.
In order, however, that an object not in contact with the body should
be perceived, there are physical as well as physiological conditions
to be fulfilled. There must be some physical process which takes place
at the surface of the body when the object in question is suitably
situated, but not otherwise; and there must be sense-organs capable of
being affected by such a process. There are, as we know from physics,
many processes which fulfil the necessary physical conditions, but
fail to affect us through the inadequacy of our sense-organs. Waves of
a certain sort make sound, but waves of exactly the same sort become
inaudible if they are too short. Waves of a certain sort make light,
but if they are too long or too short they are invisible. The waves
used in wireless are of the same sort as those that make light, but are
too long. There is no reason _a priori_ why we should not be aware of
wireless messages through our senses, without the need of instruments.
X-rays are also of the same sort as those that make light, but in this
case they are too short to be seen. They might render the objects from
which they come visible, if we had a different sort of eye. We are not
sensitive to magnetism, unless it is enormously powerful; but if we
had more iron in our bodies, we might have no need of the mariner’s
compass. Our senses are a haphazard selection of those that the nature
of physical processes renders possible; one may suppose that they have
resulted from chance variation and the struggle for existence.

It is important to observe that our perceptions are very largely
concerned with form or shape or structure. This is the point emphasised
by what is called “_Gestaltpsychologie_”, or psychology of form.
Reading is a case in point. Whether we read black letters on white
paper or white letters on a blackboard is a matter which we hardly
notice; it is the forms of the letters that affect us, not their colour
or their size (so long as they remain legible). In this matter, the
sense of sight is pre-eminent, although blind men (and others to a less
degree) can acquire a good knowledge of form by the sense of touch.

Another point of importance about our perceptions is that they give us,
within limits, a knowledge of temporal sequence. If you say to a man
“Brutus killed Cæsar”, and then “Cæsar killed Brutus”, the difference
between the two statements is likely to be perceived by him if he
is listening; in the one case he will say “of course”, in the other
“nonsense”, which is evidence of his having different perceptions in
the two cases, according to our definition. Further, if you ask him
what the difference is, he can tell you that it is a difference in the
order of the words. Thus time-order within a short period of time is
clearly perceptible.

The objective method, which we have been applying in this chapter, is
the only possible one in studying the perceptions of animals or of
infants before they can talk. Many animals too low in the scale of
evolution to have eyes are yet sensitive to light, in the sense that
they move towards it or move away from it. Such animals, according to
our criterion, perceive light, though there is no reason to suppose
that they perceive colour or visual form or anything beyond the bare
presence of light. We can perceive the bare presence of light when our
eyes are shut; perhaps one may imagine their sensitiveness to be more
or less analogous in its limitations.

It is not to be supposed, in any case, that “perceiving” an object
involves knowing what it is like. That is quite another matter.
We shall see later that certain inferences, of a highly abstract
character, can be drawn from our perceptions to the objects perceived;
but these inferences are at once difficult and not quite certain. The
idea that perception, in itself, reveals the character of objects,
is a fond delusion, and one, moreover, which it is very necessary to
overcome if our philosophy is to be anything more than a pleasant
fairy-tale.




CHAPTER VI

MEMORY OBJECTIVELY REGARDED


We are concerned in these chapters with what we can know about other
men by merely observing their behaviour. In this chapter, I propose
to consider everything that would commonly be called “memory”, in so
far as it can be made a matter of external observation. And perhaps it
may be as well, at this point, to state my own view of the question
of “behaviourism”. This philosophy, of which the chief protagonist is
Dr. John B. Watson, holds that everything that can be known about man
is discoverable by the method of external observation, _i.e._ that
none of our knowledge depends, essentially and necessarily, upon data
in which the observer and the observed are the same person. I do not
fundamentally agree with this view, but I think it contains much more
truth than most people suppose, and I regard it as desirable to develop
the behaviourist method to the fullest possible extent. I believe that
the knowledge to be obtained by this method, so long as we take physics
for granted, is self-contained, and need not, at any point, appeal
to data derived from introspection, _i.e._ from observations which a
man can make upon himself but not upon any one else. Nevertheless,
I hold that there are such observations and that there is knowledge
which depends upon introspection. What is more, I hold that data of
this kind are required for a critical exposition of physics, which
behaviourism takes for granted. I shall, therefore, after setting forth
the behaviourist view of man, proceed to a scrutiny of our knowledge of
physics, returning thence to man, but now as viewed from within. Then,
finally, I shall attempt to draw conclusions as to what we know of the
universe in general.

The word “memory” or “remembering” is commonly used in a number
of different senses, which it is important to distinguish. More
especially, there is a broad sense, in which the word applies to the
power of repeating any habitual act previously learnt, and a narrow
sense, in which it applies only to recollection of past events. It is
in the broad sense that people speak of a dog remembering his master or
his name, and that Sir Francis Darwin spoke of memory in plants. Samuel
Butler used to attribute the sort of behaviour that would usually be
called instinctive to memory of ancestral experience, and evidently he
was using the word “memory” in its widest possible sense. Bergson, on
the contrary, dismisses “habit-memory” as not true memory at all. True
memory, for him, is confined to the recollection of a past occurrence,
which, he maintains, cannot be a habit, since the event remembered
only occurred once. The behaviourist maintains that this contention is
mistaken, and that all memory consists in the retention of a habit. For
him, therefore, memory is not something requiring special study, but
is merged into the study of habit. Dr. Watson says: “The behaviourist
never uses the term ‘memory’. He believes that it has no place in an
objective psychology.” He proceeds to give instances, beginning with a
white rat in a maze. On the first occasion, he says, it took this rat
forty minutes to get out of the maze, but after thirty-five trials he
learnt to get out in six seconds, without taking any wrong turnings. He
was then kept away from the maze for six months, and on being put in it
again he got out in two minutes, with six mistakes. He was just as good
as he had been before at the twentieth trial. We have here a measure of
the extent to which the habit of the maze had been retained. A similar
experiment with a monkey showed even more retentiveness. He was put
into a problem box which at first took him twenty minutes to open, but
at the twentieth trial he opened it in two seconds. He was then kept
away from it for six months, and on being put back in it he opened it
in four seconds.

With human beings, we know that many of the habits we learn are
retained through long periods of disuse--skating, bicycling, swimming,
golf, etc., are familiar instances. Perhaps Dr. Watson goes a trifle
too far when he says: “If a poor shot or an inexpert golfer tells you
that he was good five years ago but that lack of practice has made him
poor, don’t believe him; he never was good!” At any rate, this is not
the belief of violinists and pianists, who consider it essential to
practise every day. But even if it be somewhat of an exaggeration, it
is certainly true that we retain bodily habits pretty well. Some, such
as swimming, seem to be more completely retained than others. The power
of talking a foreign language, for example, is one which is greatly
impaired by disuse. The whole matter is quantitative, and easily tested
by experiment.

But memory in the sense of recollection of past events, if it can be
explained as a habit, will have, one might suppose, to be a _verbal_
habit. As to this, Dr. Watson says:

“What the man on the street ordinarily means by an exhibition of memory
is what occurs in some such situation as this: An old friend comes to
see him, after many years’ absence. The moment he sees this friend,
he says: ‘Upon my life! Addison Sims of Seattle! I haven’t seen you
since the World’s Fair in Chicago. Do you remember the gay parties we
used to have in the Wilderness Hotel? Do you remember the Midway? Do
you remember ... etc.,’ _ad infinitum_. The psychology of this process
is so simple that it seems almost an insult to your intelligence to
discuss it, and yet a good many of the behaviourists’ kindly critics
have said that behaviourism cannot adequately explain memory. Let us
see if this is a fact.”

He goes on to say that during the period, long ago, when the man on
the street was seeing Mr. Sims, they formed verbal and manual habits
towards one another, so that “finally, just the sight of man, even
after months of absence, would call out not only the old verbal
habits, but many other types of bodily and visceral responses.”

He sums up: “By ‘memory’, then, we mean nothing except the
fact that when we meet a stimulus again after an absence, we
do the old habitual thing (say the old words and show the old
visceral--emotional--behaviour) that we learned to do when we were in
the presence of that stimulus in the first place.”

This theory is preferable to ordinary psychological theories in many
ways. In the first place, it is not an attempt to treat memory as
some sort of mystical “faculty”, and does not suppose that we are
always remembering everything that we should remember if a suitable
stimulus were applied. It is concerned with the causation of specific
acts of remembering, these acts being all externally observable. I do
not see any good reason to question it. Bergson’s contention that the
recollection of a unique occurrence cannot be explained by habit is
clearly fallacious. There are many instances, both with animals and
with human beings, of a habit becoming firmly established through one
experience. It is, therefore, quite possible that a stimulus associated
with a previous occurrence should set going a train of bodily events
which, in turn, produce words describing that occurrence. There is
here, however, a difficulty. The memory of a past occurrence cannot
be a _verbal_ habit, except when the occurrence has been frequently
related. When Watson’s man on the street says “Do you remember the
Midway”, he is not using words that have become habitual; very likely
he never used these words before. He is using words which a verbal
habit associates with an event that is now happening in him, and the
event is called up by a habit associated with Mr. Sims. So at least
we must suppose, if we accept Watson’s view. But this diminishes the
plausibility and the verifiability of his view. It is not our actual
language that can be regarded as habitual, but only what our words
express. In repeating a poem we have learned by heart, the language is
habitual, but not so when we recount a past incident in words we never
used before. In this case, it is not the actual words that we repeat,
but only their meaning. The habitual element, therefore, if it really
accounts for the recollection, must not be sought in words.

This is something of a difficulty in the Watsonian theory of language.
When a rat learns a maze, it learns certain definite bodily movements;
so do we when we learn by heart. But I may say to one person, “I met
Mr. Jones in the train to-day”, and to another “Joseph was in the
9.35 this morning.” With the exception of the words “in the”, these
two sentences have nothing verbally in common, yet they may relate
the same fact, and I may use either indifferently when I recall the
fact. Thus my recollection is certainly _not_ a definite verbal
habit. Yet words are the only overt bodily movements by which I make
known my recollections to other people. If the behaviourist tells me
that my recollection is bodily habit, and begins by telling me that
it is a _verbal_ habit, he can be driven by such instances to the
admission that it must be some other kind of habit. If he says this,
he is abandoning the region of observable fact, and taking refuge in
hypothetical bodily movements invoked to save a theory. But these are
hardly any better than “thoughts.”

This question is more general than the problem of memory. Many
different forms of words may be used to express the same “meaning”, and
there seems no reason in mere habit to account for the fact that we
sometimes use one form of words and sometimes another when we “think”
of that which all the various forms of words express. The association
seems to go, not direct from stimulus to words, but from stimulus to
“meaning” and thence to words expressing the “meaning”. You may, for
instance, be quite unable to recollect whether you were told “Jacob is
older than Joseph”, or “Joseph is younger than Jacob”, though you may
remember quite definitely that you were told the fact which both these
forms of words express. Again, if you are learning, say, a proof of a
mathematical theorem, you do not learn by heart what the book says,
unless you are a very bad mathematician; you learn, as people say, to
“understand” the proof, and then you can reproduce it in symbols quite
different from those in the book. It is such facts, among others, that
make it difficult to explain the mechanism of association, whether in
memory or in “thought” in general, if we assume that words, or even
sentences, are the terms associated.

Perhaps, however, the theory as to the “meaning” of words which we
developed in an earlier chapter may help us out of the difficulty.
We defined the “meaning” of a word by means of its associations;
therefore, if two words are synonyms, they have the same associations;
and any stimulus which calls up one may also call up the other. The
question which of two synonyms we use will then depend upon some
extraneous circumstance.

This is all very well so far as single words are concerned; it would
account satisfactorily, for instance, for the fact that I call a man
sometimes by his surname and sometimes by his Christian name. But it
is hardly so adequate when we come to the question of sentences. To
revert to the illustration of a moment ago, in response to the stimulus
“Did anything happen on your journey?” you may say either “I met Mr.
Jones in the train to-day”, or “Joseph was in the 9.35 this morning”,
or any one of an indefinite number of other sentences expressive of the
same occurrence. Are we to suppose that, while you were in the train,
you were rehearsing all these different sentences to yourself, so that
each of them became firmly associated with the words “journey to-day”?
Clearly such a supposition would be absurd. Yet all the separate words
of your sentence have many other associations; it is only the sentence
as a whole that is associated with your journey. You have met other
people besides Mr. Jones; you have had other contacts with Mr. Jones
besides meeting him this morning; “train” and “to-day” equally are
appropriate to other occurrences that you might relate. Thus it has
to be the whole sentence that is the associative unit, and yet the
sentence may never have been in your head before. It seems clear that
it is possible to state in words something that you remember, although
you never put it into words before. Suppose I say “What did you have
for breakfast to-day?” Probably you will be able to tell me, though
it is very likely that you have not given names to the things you ate
until this moment.

This whole matter is connected with the distinction between sentences
and single words, which we found important when we were discussing
language. But even when we confine ourselves to single words, there
are difficulties in Dr. Watson’s view. Cases are alleged in which
children, after learning to speak, can recall incidents which occurred
before they could speak, and describe them in correct words. This would
show that the memory had persisted in a non-verbal form throughout
the period before they learned to speak, and had only subsequently
found verbal expression. Such extreme incidents are rare and might be
questioned, but in a less extreme form it ought not to be difficult to
obtain examples of the same sort of thing. Suppose, for example, that a
young child hurt his wrist badly before he knew the word “wrist”, and
that some time afterwards he learnt it; I should not be surprised if he
could relate that he had hurt his wrist. Such instances, however, would
not refute the essence of Watson’s theory. He would allow “visceral”
memory, for example, and the association with the word “wrist” might
be grafted on to this. The real difficulty in Dr. Watson’s view, to my
mind, is the fact that our sentence may vary verbally as much as it
likes so long as it retains the same “meaning”, and that we clearly do
not rehearse to ourselves beforehand all the possible sentences having
the “meaning” in question.

It should be realised that behaviourism loses much of its
attractiveness if it is compelled to postulate movements that no one
can observe and that there is no other reason to assume. Dr. Broad,
in his book on _The Mind and its Place in Nature_, distinguishes
between “molar” and “molecular” behaviourism: the former assumes only
such bodily movements as can be observed, while the latter allows
and utilises hypothetical minute movements, more especially in the
brain. Now here we must make a distinction. Physics believes in a large
number of phenomena which are too minute to be observed even with the
strongest microscope, and if physics is at all correct, there must be
minute movements in all parts of a human body, of a sort which we can
never hope to see. We cannot reasonably demand of the behaviourist that
he should abstain from an hypothesis which physics asserts for very
good reasons. And in the process which leads from stimulus to reaction
there are bound to be small occurrences in the brain, which, though
they cannot be observed, are essential to the physiological explanation
of what occurs. But when the behaviourist assumes small occurrences
for which there is no ground in physics, and which are needed solely
in order to safeguard his theory, he is in a less strong position.
Dr. Watson asserts, for instance, that whenever we “think” there are
small movements in the larynx which are beginnings of the movements we
should make as if we spoke words out loud. It may be that this is true;
certainly I am not prepared to deny it. But I am not prepared to say
that it _must_ be true merely because, if it were not, behaviourism
would be false. We do not know in advance that behaviourism is true;
we have to find out whether it will explain observed facts. Whenever
it has to postulate something unobserved merely in order to avoid a
refutation, it weakens its case. And if it maintains, as, from Dr.
Watson’s language, it seems to do, that we only remember an occurrence
by forming a verbal habit in connection with it, then it is obliged to
postulate much implicit use of words of which we have no evidence.

To sum up this discussion. While it is quite possible, by behaviourist
methods, to ascertain whether a person remembers a past occurrence or
not, unless he is deliberately obstructing the observer, and while
much memory can be quite adequately explained as habit, there do seem
to be great difficulties in the view that memory consists _entirely_
of habit, at least in the case of the recollection of an event. These
difficulties seem insuperable if we suppose memory to be _essentially_
a verbal habit. They are not insuperable if we postulate sufficient
minute unobservable bodily movements. We have not considered whether
they can be overcome by introducing data derived from introspection,
since we wish, for the present, to maintain a strictly objective
attitude to human behaviour. The introspective discussion of memory
will be taken up at a later stage.




CHAPTER VII

INFERENCE AS A HABIT


In this chapter, we are concerned with inference as it can be observed
when practised by some one else. Inference is supposed to be a mark of
intelligence and to show the superiority of men to machines. At the
same time, the treatment of inference in traditional logic is so stupid
as to throw doubt on this claim, and syllogistic inference, which was
taken as the type from Aristotle to Bacon (exclusive), is just the sort
of thing that a calculating machine could do better than a professor.
In syllogistic inference, you are supposed to know already that all
men are mortal and that Socrates is a man; hence you deduce, what you
never suspected before, that Socrates is mortal. This form of inference
does actually occur, though very rarely. The only instance I have ever
heard of was supplied by Dr. F. C. S. Schiller. He once produced a
comic number of the philosophical periodical _Mind_, and sent copies to
various philosophers, among others to a certain German, who was much
puzzled by the advertisements. But at last he argued: “Everything in
this book is a joke, therefore the advertisements are jokes”. I have
never come across any other case of new knowledge obtained by means of
a syllogism. It must be admitted that, for a method which dominated
logic for two thousand years, this contribution to the world’s stock of
information cannot be considered very weighty.

The inferences that we actually make in daily life differ from those
of syllogistic logic in two respects, namely, that they are important
and precarious, instead of being trivial and safe. The syllogism may be
regarded as a monument to academic timidity: if an inference might be
wrong, it was dangerous to draw it. So the mediæval monks, in their
thinking as in their lives, sought safety at the expense of fertility.

With the Renaissance, a more adventurous spirit came into the world,
but at first in philosophy, it only took the form of following Greeks
other than Aristotle, and more especially Plato. It is only with Bacon
and Galileo that the inductive method arrived at due recognition:
with Bacon as a programme which was largely faulty, but with Galileo
as something which actually led to brilliant results, namely, the
foundation of modern mathematical physics. Unfortunately, when the
pedants got hold of induction, they set to work to make it as tame and
scholastic as deduction had been. They searched for a way of making
it _always_ lead to true results, and in so doing robbed it of its
adventurous character. Hume turned upon them with sceptical arguments,
proving quite conclusively that if an induction is worth making it may
be wrong. Thereupon Kant deluged the philosophic world with muddle and
mystery, from which it is only now beginning to emerge. Kant has the
reputation of being the greatest of modern philosophers, but to my mind
he was a mere misfortune.

Induction, as it appears in the text-books, consists, roughly
speaking, in the inference that, because A and B have been found often
together and never apart, therefore they are probably always together,
and either may be taken as a sign of the other. I do not wish, at
this stage, to examine the logical justification of this form of
argumentation; for the present, I am considering it as a _practice_,
which we can observe in the habits of men and animals.

As a practice, induction is nothing but our old friend, the law of
conditioned reflexes or of association. A child touches a knob that
gives him an electric shock; after that, he avoids touching the knob.
If he is old enough to speak he may state that the knob hurts when it
is touched; he has made an induction based on a single instance. But
the induction will exist as a bodily habit even if he is too young
to speak, and it occurs equally among animals, provided they are not
too low in the scale. The theories of induction in logic are what
Freudians call a “rationalisation”; that is to say, they consist of
reasons invented afterwards to prove that what we have been doing is
sensible. It does not follow that they are bad reasons; in view of the
fact that we and our ancestors have managed to exist since the origin
of life, our behaviour and theirs must have been fairly sensible, even
if we and they were unable to prove that it was. This, however, is not
the point that concerns us at present. What concerns us at present is
the fact that verbal induction is a late development of induction in
behaviour, which is nothing more or less than the principle of “learned
reactions”.

This principle, as the reader will remember, states that, if a
certain event calls out a certain response, and if another event is
experienced just before it, or at the same moment, in time that other
event will tend to call out the response which, originally, only
the first event would call out. This applies both to muscles and to
glands; it is because it applies to glands that words are capable of
causing emotions. Moreover, we cannot set limits to the length of the
chain of associations that may be established. If you hold an infant’s
limbs, you call out a rage reaction; this appears to be an “unlearned
reaction”. If you, and no one else, repeatedly hold an infant’s limbs,
the mere sight of you will call out a rage reaction after a time.
When the infant learns to talk your name may have the same effect.
If, later, he learns that you are an optician, he may come to hate
all opticians; this may lead him to hate Spinoza because he made
spectacles, and thence he may come to hate metaphysicians and Jews.
For doing so he will no doubt have the most admirable reasons, which
will seem to him to be his real ones; he will never suspect the process
of conditioning by which he has in fact arrived at his enthusiasm for
the Ku Klux Klan. This is an example of conditioning in the emotional
sphere; but it is rather in the muscular sphere that we must seek the
origin of the practice of induction.

Domestic animals which are habitually fed by a certain person will run
towards that person as soon as they see him. We say that they expect
food, and in fact their behaviour is very like what it would be if
they saw food. But really we have only an example of “conditioning”:
they have often seen first the farmer and then the food, so that in
time they react to the farmer as they originally reacted to the food.
Infants soon learn to react to the sight of the bottle, although at
first they only react to the touch of it. When they can speak, the same
law makes them say “dinner” when they hear the dinner-bell. It is quite
unnecessary to suppose that they first think “that bell means dinner”,
and then say “dinner”. The sight of dinner (by previous “learned
reaction”) causes the word “dinner”: the bell frequently precedes the
sight of dinner; therefore in time the bell produces the word “dinner”.
It is only subsequent reflection, probably at a much later age, that
makes the child say “I knew dinner was ready because I heard the bell”.
Long before he can say this, he is acting as if he knew it. And there
is no good reason for denying that he knows it, when he acts as if he
did. If knowledge is to be displayed by behaviour, there is no reason
to confine ourselves to _verbal_ behaviour as the sole kind by which
knowledge can manifest itself.

The situation, stated abstractly, is as follows. Originally, stimulus
A produced reaction C; now stimulus B produces it, as a result of
association. Thus B has become a “sign” of A, in the sense that it
causes the behaviour appropriate to A. All sorts of things may be signs
of other things, but with human beings words are the supreme example of
signs. All signs depend upon some practical induction. Whenever we read
or hear a statement, its effect upon us depends upon induction in this
sense, since the words are signs of what they mean, in the sense that
we react to them, in certain respects, as we should to what they stand
for. If some one says to you “your house is on fire”, the effect upon
you is practically the same as if you saw the conflagration. You may,
of course, be the victim of a hoax, and in that case your behaviour
will not be such as achieves any purpose you have in view. This risk
of error exists always, since the fact that two things have occurred
together in the past cannot prove conclusively that they will occur
together in the future.

Scientific induction is an attempt to regularise the above process,
which we may call “physiological induction”. It is obvious that, as
practised by animals, infants, and savages, physiological induction is
a frequent source of error. There is Dr. Watson’s infant who induced,
from two examples, that whenever he saw a certain rat there would be
a loud noise. There is Edmund Burke, who induced from one example
(Cromwell) that revolutions lead to military tyrannies. There are
savages who argue, from one bad season, that the arrival of a white
man causes bad crops. The inhabitants of Siena, in 1348, thought
that the Black Death was a punishment for their pride in starting to
build too large a cathedral. Of such examples there is no end. It is
very necessary, therefore, if possible, to find some method by which
induction can be practised so as to lead, in general, to correct
results. But this is a problem of scientific method, with which we will
not yet concern ourselves.

What does concern us at present is the fact that all inference, of
the sort that really occurs, is a development of this one principle
of conditioning. In practice, inference is of two kinds, one typified
by induction, the other by mathematical reasoning. The former is by
far the more important, since, as we have seen, it covers all use of
signs and all empirical generalisations as well as the habits of which
they are the verbal expression. I know that, from the traditional
standpoint, it seems absurd to talk of inference in most cases of this
sort. For example, you find it stated in the paper that such and such a
horse has won the Derby. According to my own use of words, you practise
an induction when you arrive thence at the belief that that horse has
won. The stimulus consists of certain black marks on white paper--or
perhaps on pink paper. This stimulus is only connected with horses
and the Derby by association, yet your reaction is one appropriate
to the Derby. Traditionally, there was only inference where there
was a “mental process”, which, after dwelling upon the “premisses”,
was led to assert the “conclusion” by means of insight into their
logical connection. I am not saying that the process which such words
as the above are intended to describe never takes place; it certainly
does. What I am saying is that, genetically and causally, there is no
important difference between the most elaborate induction and the most
elementary “learned reaction”. The one is merely a developed form of
the other, not something radically different. And our determination to
believe in the results of inductions, even if, as logicians, we see
no reason to do so, is really due to the potency of the principle of
association; it is an example--perhaps the most important example--of
what Dr. Santayana calls “animal faith”.

The question of mathematical reasoning is more difficult. I think we
may lay it down that, in mathematics, the conclusion always asserts
merely the whole or part of the premisses, though usually in new
language. The difficulty of mathematics consists in seeing that
this is so in particular cases. In practice, the mathematician has
a set of rules according to which his symbols can be manipulated,
and he acquires technical skill in working according to the rules
in the same sort of way as a billiard-player does. But there is a
difference between mathematics and billiards: the rules of billiards
are arbitrary, whereas in mathematics some at least are in some sense
“true”. A man cannot be said to understand mathematics unless he
has “seen” that these rules are right. Now what does this consist
of? I think it is only a more complicated example of the process of
understanding that “Napoleon” and “Bonaparte” refer to the same person.
To explain this, however, we must revert to what was said, in the
chapter on “Language”, about the understanding of form.

Human beings possess the power of reacting to form. No doubt some of
the higher animals also possess it, though to nothing like the same
extent as men do; and all animals, except a few of the most intelligent
species, appear to be nearly devoid of it. Among human beings, it
differs greatly from one individual to another, and increases, as a
rule, up to adolescence. I should take it as what chiefly characterises
“intellect”. But let us see, first, in what the power consists.

When a child is being taught to read, he learns to recognise a given
letter, say H, whether it is large or small, black or white or red.
However it may vary in these respects his reaction is the same: he
says “H”. That is to say, the essential feature in the stimulus is its
_form_. When my boy, at the age of just under three, was about to eat a
three-cornered piece of bread and butter, I told him it was a triangle.
(His slices were generally rectangular.) Next day, unprompted, he
pointed to triangular bits in the pavement of the Albert Memorial, and
called them “triangles”. Thus the form of the bread and butter, as
opposed to its edibility, its softness, its colour, etc., was what had
impressed him. This sort of thing constitutes the most elementary kind
of reaction to form.

Now “matter” and “form” can be placed, as in the Aristotelian
philosophy, in a hierarchy. From a triangle we can advance to a
polygon, thence to a figure, thence to a manifold of points. Then we
can go on and turn “point” into a formal concept, meaning “something
that has relations which resemble spatial relations in certain formal
respects”. Each of these is a step away from “matter” and further into
the region of “form”. At each stage the difficulty increases. The
difficulty consists in having a uniform reaction (other than boredom)
to a stimulus of this kind. When we “understand” a mathematical
expression, that means that we can react to it in an appropriate
manner, in fact, that it has “meaning” for us. This is also what we
mean by “understanding” the word “cat”. But it is easier to understand
the word “cat”, because the resemblances between different cats are
of a sort which causes even animals to have a uniform reaction to all
cats. When we come to algebra, and have to operate with _x_ and _y_,
there is a natural desire to know what _x_ and _y_ really are. That,
at least, was my feeling: I always thought the teacher knew what they
really were, but would not tell me. To “understand” even the simplest
formula in algebra, say (x + y)² = x² + 2xy + y², is to be able to
react to two sets of symbols in virtue of the form which they express,
and to perceive that the form is the same in both cases. This is a
very elaborate business, and it is no wonder that boys and girls find
algebra a bugbear. But there is no novelty _in principle_ after the
first elementary perceptions of form. And perception of form consists
merely in reacting alike to two stimuli which are alike in form but
very different in other respects. For, when we can do that, we can say,
on the appropriate occasion, “that is a triangle”; and this is enough
to satisfy the examiner that we know what a triangle is, unless he is
so old-fashioned as to expect us to reproduce the verbal definition,
which is of course a far easier matter, in which, with patience, we
might teach even a parrot to succeed.

The meanings of complex mathematical symbols are always fixed by rules
in relation to the meaning of simpler symbols; thus their meanings are
analogous to those of sentences, not to those of single words. What was
said earlier about the understanding of sentences applies, therefore,
to any group of symbols which, in mathematics, will be declared to have
the same meaning as another group, or part of that meaning.

We may sum up this discussion by saying that mathematical inference
consists in attaching the same reactions to two different groups of
signs, whose meanings are fixed by convention in relation to their
constituent parts, whereas induction consists, first, in taking
something as a sign of something else, and later, when we have learned
to take A as a sign of B, in taking A as also a sign of C. Thus the
usual cases of induction and deduction are distinguished by the fact
that, in the former, the inference consists in taking one sign as
a sign of two different things, while in the latter the inference
consists in taking two different signs as signs of the same thing.
This statement is a little too antithetical to be taken as an exact
expression of the whole truth in the matter. What is true, however, is
that both kinds of inferences are concerned with the relation of a sign
to what it signifies, and therefore come within the scope of the law of
association.




CHAPTER VIII

KNOWLEDGE BEHAVIOURISTICALLY CONSIDERED


The word “knowledge”, like the word “memory”, is avoided by the
behaviourist. Nevertheless there is a phenomenon commonly called
“knowledge”, which is tested behaviouristically in examinations. I want
to consider this phenomenon in this chapter, with a view to deciding
whether there is anything in it that the behaviourist cannot deal with
adequately.

It will be remembered that, in Chapter II, we were led to the view that
knowledge is a characteristic of the complete process from stimulus to
reaction, or even, in the cases of sight and hearing, from an external
object to a reaction, the external object being connected with the
stimulus by a chain of physical causation in the outer world. Let us,
for the moment, leave on one side such cases as sight and hearing, and
confine ourselves, for the sake of definiteness, to knowledge derived
from touch.

We can observe touch producing reactions in quite humble animals, such
as worms and sea anemones. Are we to say that they have “knowledge”
of what they touch? In some sense, yes. Knowledge is a matter of
degree. When it is regarded in a purely behaviouristic manner, we
shall have to concede that it exists, in some degree, wherever there
is a characteristic reaction to a stimulus of a certain kind, and this
reaction does not occur in the absence of the right kind of stimulus.
In this sense, “knowledge” is indistinguishable from “sensitivity”,
which we considered in connection with perception. We might say that
a thermometer “knows” the temperature, and that a compass “knows” the
direction of the magnetic north. This is the only sense in which, on
grounds of observation, we can attribute knowledge to animals that
are low in the scale. Many animals, for example, hide themselves when
exposed to light, but as a rule not otherwise. In this, however, they
do not differ from a radiometer. No doubt the mechanism is different,
but the observed molar motion has similar characteristics. Wherever
there is a reflex, an animal may be said, in a sense, to “know” the
stimulus. This is, no doubt, not the usual sense of “knowledge”, but it
is the germ out of which knowledge in the usual sense has grown, and
without which no knowledge would be possible.

Knowledge in any more advanced sense is only possible as a result of
learning, in the sense considered in Chapter III. The rat that has
learned the maze “knows” the way out of it; the boy who has learned
certain verbal reactions “knows” the multiplication table. Between
these two cases there is no important difference. In both cases, we
say that the subject “knows” something because he reacts in a manner
advantageous to himself, in which he could not react before he had had
certain experiences. I do not think, however, that we ought to use such
a notion as “advantageous” in connection with knowledge. What we can
observe, for instance, with the rat in the maze, is violent activity
until the food is reached, followed by eating when it is reached; also
a gradual elimination of acts which do not lead to the food. Where this
sort of behaviour is observed, we may say that it is directed towards
the food, and that the animal “knows” the way to the food when he gets
to it by the shortest possible route.

But if this view is right, we cannot define any knowledge acquired
by learning except with reference to circumstances toward which an
animal’s activity is directed. We should say, popularly, that the
animal “desires” such circumstances. “Desire”, like “knowledge”,
is capable of a behaviouristic definition, and it would seem that
the two are correlative. Let us, then, spend a little time on the
behaviouristic treatment of “desire”.

The best example of desire, from this point of view, is hunger. The
stimulus to hunger is a certain well-ascertained bodily condition.
When in this condition, an animal moves restlessly; if he sees or
smells food, he moves in a manner which, in conditions to which he is
accustomed, would bring him to the food; if he reaches it, he eats it,
and if the quantity is sufficient he then becomes quiescent. This kind
of behaviour may be summarised by saying that a hungry animal “desires”
food. It is behaviour which is in various ways different from that of
inanimate matter, because restless movements persist until a certain
condition is realised. These movements may or may not be the best
adapted to realising the condition in question. Every one knows about
the pike that was put on one side of a glass partition, with minnows
on the other side. He continually bumped his nose on the glass, and
after six weeks gave up the attempt to catch them. When, after this,
the partition was removed, he still refrained from pursuing them. I do
not know whether the experiment was tried of leaving a possibility of
getting to the minnows by a roundabout route. To have learned to take a
roundabout route would perhaps have required a degree of intelligence
beyond the capacity of fishes; this is a matter, however, which offers
little difficulty to dogs or monkeys.

What applies to hunger applies equally to other forms of “desire”.
Every animal has a certain congenital apparatus of “desires”; that
is to say, in certain bodily conditions he is stimulated to restless
activities which tend towards the performance of some reflex, and
if a given situation is often repeated the animal arrives more and
more quickly at the performance of the reflex. This last, however, is
only true of the higher animals; in the lower, the whole process from
beginning to end is reflex, and can therefore only succeed in normal
circumstances. The higher animals, and more especially men, have a
larger proportion of learning and a smaller proportion of reflexes in
their behaviour, and are therefore better able to adapt themselves
to new circumstances. The helplessness of infants is a necessary
condition for the adaptability of adults; infants have fewer useful
reflexes than the young of animals, but have far more power of forming
useful habits, which can be adapted to circumstances and are not
fatally fixed from birth. This fact is intimately connected with the
superiority of the human intelligence above that of the brutes.

Desire is extremely subject to “conditioning”. If A is a primitive
desire and B has on many occasions been a means to A, B comes to be
desired in the same sense in which A was previously desired. It may
even happen, as in misers, that the desire for B completely displaces
the desire for A, so that B, when attained, is no longer used as a
means to A. This, however, is more or less exceptional. In general, the
desire for A persists, although the desire for B has a more or less
independent life.

The “conditioning” of primitive desires in human beings is the source
of much that distinguishes our life from that of animals. Most animals
only seek food when they are hungry; they may, then, die of starvation
before they find it. Men, on the contrary, must have early acquired
pleasure in hunting as an art, and must have set out on hunting
expeditions before they were actually hungry. A further stage in the
conditioning of hunger came with domestic animals; a still further
stage with agriculture. Nowadays, when a man sets to work to earn his
living, his activity is still connected, though not very directly,
with hunger and the other primitive desires that can be gratified by
means of money. These primitive desires are still, so to speak, the
power station, though their energy is widely distributed to all sorts
of undertakings that seem, at first sight, to have no connection with
them. Consider “freedom” and the political activities it inspires; this
is derivable, by “conditioning”, from the emotion of rage which Dr.
Watson observed in infants whose limbs are not “free”. Again we speak
of the “fall” of empires and of “fallen” women; this is connected with
the fear which infants display when left without support.

After this excursion into the realm of desire, we can now return to
“knowledge”, which, as we saw, is a term correlative to “desire”, and
applicable to another feature of the same kind of activity. We may say,
broadly, that a response to a stimulus of the kind involving desire
in the above sense shows “knowledge” if it leads by the quickest or
easiest route to the state of affairs which, in the above sense, is
behaviouristically the object of desire. Knowledge is thus a matter
of degree: the rat, during its progressive improvements in the maze,
is gradually acquiring more and more knowledge. Its “intelligence
quotient”, so far as that particular task is concerned, will be the
ratio of the time it took on the first trial to the time it takes now
to get out of the maze. Another point, if our definition of knowledge
is accepted, is, that there is no such thing as purely contemplative
knowledge: knowledge exists only in relation to the satisfaction of
desire, or, as we say, in the capacity to choose the right means to
achieve our ends.

But can such a definition as the above really stand? Does it represent
at all the sort of thing that would commonly be called knowledge? I
think it does in the main, but there is need of some discussion to make
this clear.

In some cases, the definition is obviously applicable. These are the
cases that are analogous to the rat in the maze, the consideration of
which led us to our definition. Do you “know” the way from Trafalgar
Square to St. Pancras? Yes, if you can walk it without taking any wrong
turnings. In practice, you can give verbal proof of such knowledge,
without actually having to walk the distance; but that depends upon
the correlation of names with streets, and is part of the process of
substituting words for things. There may, it is true, come doubtful
cases. I was once on a bus in Whitehall, and my neighbour asked “What
street is this?” I answered him, not without surprise at his ignorance.
He then said, “What building is that?” and I replied “The Foreign
Office”. To this he retorted, “but I thought the Foreign Office was in
Downing Street”. This time, it was his knowledge that surprised me.
Should we say that he knew where the Foreign Office is? The answer is
yes or no according to his purpose. From the point of view of sending a
letter to it, he knew; from the point of view of walking to it, he did
not know. He had, in fact, been a British Consul in South America, and
was in London for the first time.

But now let us come to cases less obviously within the scope of our
definition. The reader “knows” that Columbus crossed the ocean in
1492. What do we mean by saying that he “knows” this? We mean, no
doubt, primarily that writing down this statement is the way to pass
examinations, which is just as useful to us as getting out of the
maze is to the rat. But we do not mean only this. There is historical
evidence of the fact, at least I suppose there is. The historical
evidence consists of printed books and manuscripts. Certain rules have
been developed by historians as to the conditions in which statements
in books or manuscripts may be accepted as true, and the evidence in
our case is (I presume) in accordance with these rules. Historical
facts often have importance in the present; for example, wills, or
laws not yet repealed. The rules for weighing historical evidence
are such as will, in general bring out self-consistent results. Two
results are self-consistent when, in relation to a desire to which both
are relevant, they enjoin the same action, or actions which can form
part of the one movement towards the goal. At Coton, near Cambridge,
there is (or was in my time) a signpost with two arms pointing in
diametrically opposite directions, and each arm said “To Cambridge”.
This was a perfect example of self-contradiction, since the two arms
made statements representing exactly opposite actions. And this case
illustrates why self-contradiction is to be avoided. But the avoidance
of self-contradiction makes great demands upon us; Hegel and Bradley
imagined that we could know the nature of the universe by means of
this principle alone. In this they were pretty certainly mistaken,
but nevertheless a great deal of our “knowledge” depends upon this
principle to a greater or less extent.

Most of our knowledge is like that in a cookery book, maxims to be
followed when occasion arises, but not useful at every moment of every
day. Since knowledge may be useful at any time, we get gradually,
through conditioning, a general desire for knowledge. The learned man
who is helpless in practical affairs is analogous to the miser, in that
he has become absorbed in a means. It should be observed, also, that
knowledge is neutral as among different purposes. If you know that
arsenic is a poison, that enables you equally to avoid it if you wish
to remain in health, and to take it if you wish to commit suicide. You
cannot judge from a man’s conduct in relation to arsenic whether he
knows that it is a poison or not, unless you know his desires. He may
be tired of life, but avoid arsenic because he has been told that it
is a good medicine; in this case, his avoidance of it is evidence of
_lack_ of knowledge.

But to return to Columbus: surely, the reader will say, Columbus really
did cross the Atlantic in 1492, and that is why we call this statement
“knowledge”. This is the definition of “truth” as “correspondence with
fact”. I think there is an important element of correctness in this
definition, but it is an element to be elicited at a later stage,
after we have discussed the physical world. And it has the defect--as
pragmatists have urged--that there seems no way of getting at “facts”
and comparing them with our beliefs: all that we ever reach consists of
other beliefs. I do not offer our present behaviouristic and pragmatic
definition of “knowledge” as the only possible one, but I offer it as
the one to which we are led if we wish to regard knowledge as something
causally important, to be exemplified in our reactions to stimuli. This
is the appropriate point of view when we are studying man from without,
as we have been doing hitherto.

There is, however, within the behaviourist philosophy, one important
addition to be made to our definition. We began this chapter with
sensitivity, but we went on to the consideration of learned reactions,
where the learning depended upon association. But there is another
sort of learning--at least it is _prima facie_ another sort--which
consists of increase of sensitivity. All sensitivity in animals and
human beings must count as a sort of knowledge; that is to say, if an
animal behaves, in the presence of a stimulus of a certain kind, as it
would not behave in the absence of that stimulus then, in an important
sense, it has “knowledge” as regards the stimulus. Now it appears that
practice--_e.g._ in music--very greatly increases sensitivity. We
learn to react differently to stimuli which only differ sightly; what
is more, we learn to react to differences. A violin-player can react
with great precision to an interval of a fifth; if the interval is very
slightly greater or less, his behaviour in tuning is influenced by the
difference from a fifth. And as we have already had occasion to notice,
we become, through practice, increasingly sensitive to form. All this
increased sensitivity must count as increase of knowledge.

But in saying this we are not saying anything inconsistent with our
earlier definition of knowledge. Sensitivity is essential to choosing
the right reaction in many cases. To take the cookery-book again; when
it says “take a pinch of salt”, a good cook knows how much to take,
which is an instance of sensitivity. Accurate scientific observation,
which is of great practical importance, depends upon sensitivity. And
so do many of our practical dealings with other people: if we cannot
“feel” their moods, we shall be always getting at cross purposes.

The extent to which sensitivity is improved by practice is astonishing.
Town-bred people do not know whether the weather is warm or cold until
they read the weather reports in the paper. An entomologist perceives
vastly more beetles in the course of a country walk than other people
do. The subtlety with which connoisseurs can distinguish among wines
and cigars is the despair of youths who wish to become men of the
world. Whether this increase of sensitivity can be accounted for by
the law of association, I do not know. In many cases, probably, it can,
but I think sensitiveness to form, which is the essential element in
the more difficult forms of abstract thought as well as in many other
matters, cannot be regarded as derivative from the law of association,
but is more analogous to the development of a new sense. I should
therefore include improvement in sensitivity as an independent element
in the advancement of knowledge. But I do so with some hesitation.

The above discussion does not pretend to cover the whole of the ground
that has to be covered in discussing the definition of “knowledge”.
There are other points of view, which are also necessary to a complete
consideration of the question. But these must wait until, after
considering the physical world, we come to the discussion of man as
viewed from within.




PART II

THE PHYSICAL WORLD




CHAPTER IX

THE STRUCTURE OF THE ATOM


In all that we have said hitherto on the subject of man from without,
we have taken a common-sense view of the material world. We have not
asked ourselves: what _is_ matter? Is there such a thing, or is the
outside world composed of stuff of a different kind? And what light
does a correct theory of the physical world throw upon the process of
perception? These are questions which we must attempt to answer in the
following chapters. And in doing so the science upon which we must
depend is physics. Modern physics, however, is very abstract, and by
no means easy to explain in simple language. I shall do my best, but
the reader must not blame me too severely if, here and there, he finds
some slight difficulty or obscurity. The physical world, both through
the theory of relativity and through the most recent doctrines as to
the structure of the atom, has become very different from the world
of everyday life, and also from that of scientific materialism of the
eighteenth-century variety. No philosophy can ignore the revolutionary
changes in our physical ideas that the men of science have found
necessary; indeed it may be said that all traditional philosophies have
to be discarded, and we have to start afresh with as little respect
as possible for the systems of the past. Our age has penetrated more
deeply into the nature of things than any earlier age, and it would be
a false modesty to over-estimate what can still be learned from the
metaphysicians of the seventeenth, eighteenth and nineteenth centuries.

What physics has to say about matter, and the physical world generally,
from the standpoint of the philosopher, comes under two main heads:
first, the structure of the atom; secondly, the theory of relativity.
The former was, until recently, the less revolutionary philosophically,
though the more revolutionary in physics. Until 1925, theories of the
structure of the atom were based upon the old conception of matter as
indestructible substance, although this was already regarded as no
more than a convenience. Now, owing chiefly to two German physicists,
Heisenberg and Schrödinger, the last vestiges of the old solid atom
have melted away, and matter has become as ghostly as anything in
a spiritualist seance. But before tackling these newer views, it
is necessary to understand the much simpler theory which they have
displaced. This theory does not, except here and there, take account
of the new doctrines on fundamentals that have been introduced by
Einstein, and it is much easier to understand than relativity. It
explains so much of the facts that, whatever may happen, it must remain
a stepping-stone to a complete theory of the structure of the atom;
indeed, the newer theories have grown directly out of it, and could
hardly have arisen in any other way. We must therefore spend a little
time in giving a bare outline, which is the less to be regretted as the
theory is in itself fascinating.

The theory that matter consists of “atoms”, _i.e._ of little bits
that cannot be divided, is due to the Greeks, but with them it was
only a speculation. The evidence for what is called the atomic
theory was derived from chemistry, and the theory itself, in its
nineteenth-century form, was mainly due to Dalton. It was found that
there were a number of “elements”, and that other substances were
compounds of these elements. Compound substances were found to be
composed of “molecules”, each molecule being composed of “atoms” of one
substance combined with “atoms” of another or of the same. A molecule
of water consists of two atoms of hydrogen and one atom of oxygen; they
can be separated by electrolysis. It was supposed, until radio-activity
was discovered, that atoms were indestructible and unchangeable.
Substances which were not compounds were called “elements”. The
Russian chemist Mendeleev discovered that the elements can be arranged
in a series by means of progressive changes in their properties; in his
time, there were gaps in this series, but most of them have since been
filled by the discovery of new elements. If all the gaps were filled,
there would be 92 elements; actually the number known is 87, or,
including three about which there is still some doubt, 90. The place of
an element in this series is called its “atomic number”. Hydrogen is
the first, and has the atomic number 1; helium is the second, and has
the atomic number 2; uranium is the last, and has the atomic number 92.
Perhaps in the stars there are elements with higher atomic numbers, but
so far none has been actually observed.

The discovery of radio-activity necessitated new views as to “atoms”.
It was found that an atom of one radio-active element can break up into
an atom of another element and an atom of helium, and that there is
also another way in which it can change. It was found also that there
can be different elements having the same place in the series; these
are called “isotopes”. For example, when radium disintegrates it gives
rise, in the end, to a kind of lead, but this is somewhat different
from the lead found in lead-mines. A great many “elements” have been
shown by Dr. F. W. Aston to be really mixtures of isotopes, which can
be sorted out by ingenious methods. All this, but more especially the
transmutation of elements in radio-activity, led to the conclusion that
what had been called “atoms” were really complex structures, which
could change into atoms of a different sort by losing a part. After
various attempts to imagine the structure of an atom, physicists were
led to accept the view of Sir Ernest Rutherford, which was further
developed by Niels Bohr.

In this theory, which, in spite of recent developments, remains
substantially correct, all matter is composed of two sorts of units,
electrons and protons. All electrons are exactly alike, and all protons
are exactly alike. All protons carry a certain amount of positive
electricity, and all electrons carry an equal amount of negative
electricity. But the mass of a proton is about 1835 times that of an
electron: it takes 1835 electrons to weigh as much as one proton.
Protons repel each other, and electrons repel each other, but an
electron and a proton attract each other. Every atom is a structure
consisting of electrons and protons. The hydrogen atom, which is the
simplest, consists of one proton with one electron going round it as
a planet goes round the sun. The electron may be lost, and the proton
left alone; the atom is then positively electrified. But when it has
its electron, it is, as a whole, electrically neutral, since the
positive electricity of the proton is exactly balanced by the negative
electricity of the electron.

The second element, helium, has already a much more complicated
structure. It has a nucleus, consisting of four protons, and two
electrons very close together, and in its normal state it has two
planetary electrons going round the nucleus. But it may lose either or
both of these, and it is then positively electrified.

All the latter elements consist, like helium, of a nucleus composed of
protons and electrons, and a number of planetary electrons going round
the nucleus. There are more protons than electrons in the nucleus,
but the excess is balanced by the planetary electrons when the atom
is unelectrified. The number of protons in the nucleus gives the
“atomic weight” of the element: the excess of protons over electrons
in the nucleus gives the “atomic number”, which is also the number of
planetary electrons when the atom is unelectrified. Uranium, the last
element, has 238 protons and 146 electrons in the nucleus, and when
unelectrified it has 92 planetary electrons. The arrangement of the
planetary electrons in atoms other than hydrogen is not accurately
known, but it is clear that, in some sense, they form different rings,
those in the outer rings being more easily lost than those nearer the
nucleus.

I come now to what Bohr added to the theory of atoms as developed
by Rutherford. This was a most curious discovery, introducing, in a
new field, a certain type of discontinuity which was already known
to be exhibited by some other natural processes. No adage had seemed
more respectable in philosophy than “natura non facit saltum”, Nature
makes no jumps. But if there is one thing more than another that the
experience of a long life has taught me, it is that Latin tags always
express falsehoods; and so it has proved in this case. Apparently
Nature does make jumps, not only now and then, but whenever a body
emits light, as well as on certain other occasions. The German
physicist Planck was the first to demonstrate the necessity of jumps.
He was considering how bodies radiate heat when they are warmer
than their surroundings. Heat, as has long been known, consists of
vibrations, which are distinguished by their “frequency”, _i.e._ by the
number of vibrations per second. Planck showed that, for vibrations
having a given frequency, not all amounts of energy are possible, but
only those having to the frequency a ratio which is a certain quantity
_h_ multiplied by 1 or 2 or 3 or some other whole number, in practice
always a small whole number. The quantity _h_ is known as “Planck’s
constant”; it has turned out to be involved practically everywhere
where measurement is delicate enough to know whether it is involved or
not. It is such a small quantity that, except where measurement can
reach a very high degree of accuracy, the departure from continuity is
not appreciable.[7]

      [7] The dimensions of _h_ are those of “action”, _i.e._
          energy multiplied by time, or moment of momentum, or
          mass multiplied by length multiplied by velocity. Its
          magnitude is about 6.55 × 10.27 erg secs.

Bohr’s great discovery was that this same quantity _h_ is involved
in the orbits of the planetary electrons in atoms, and that it
limits the possible orbits in ways for which nothing in Newtonian
dynamics had prepared us, and for which so far, there is nothing in
relativity-dynamics to account. According to Newtonian principles, an
electron ought to be able to go round the nucleus in any circle with
the nucleus in the centre, or in any ellipse with the nucleus in a
focus; among possible orbits, it would select one or another according
to its direction and velocity. But in fact only certain out of all
these orbits occur. Those that occur are among those that are possible
on Newtonian principles, but are only an infinitesimal selection from
among these. It will simplify the explanation if we confine ourselves,
as Bohr did at first, to circular orbits; moreover we will consider
only the hydrogen atom, which has one planetary electron and a nucleus
consisting of one proton. To define the circular orbits that are
found to be possible, we proceed as follows: multiply the mass of the
electron by the circumference of its orbit, and this again by the
velocity of the electron; the result will always be _h_ or 2_h_, or
3_h_, or some other small exact multiple of _h_, where _h_, as before,
is “Planck’s constant”. There is thus a smallest possible orbit, in
which the above product is _h_; the radius of the next orbit, in which
the above produce is 2_h_, will have a length four times this minimum;
the next, nine times; the next, sixteen times; and so on through the
“square numbers” (_i.e._ those got by multiplying a number by itself).
Apparently no other circular orbits than these are possible in the
hydrogen atom. Elliptic orbits are possible, and these again introduce
exact multiples of _h_: but we need not, for our purposes, concern
ourselves with them.

When a hydrogen atom is left to itself, if the electron is in the
minimum orbit it will continue to rotate in that orbit so long as
nothing from outside disturbs it; but if the electron is in any of
the larger possible orbits, it may sooner or later jump suddenly to a
smaller orbit, either the minimum or one of the intermediate possible
orbits. So long as the electron does not change its orbit, the atom
does not radiate energy, but when the electron jumps to a smaller
orbit, the atom loses energy, which is radiated out in the form of a
light-wave. This light-wave is always such that its energy divided by
its frequency is exactly _h_. The atom may absorb energy from without,
and it does so by the electron jumping to a larger orbit. It may then
afterwards, when the external source of energy is removed, jump back to
the smaller orbit; this is the cause of fluorescence, since, in doing
so, the atom gives out energy in the form of light.

The same principles, with greater mathematical complications, apply
to the other elements. There is, however, with some of the latest
elements, a phenomenon which cannot have any analogue in hydrogen, and
that is radio-activity. When an atom is radio-active, it emits rays of
three kinds, called respectively α-rays, β-rays, and γ-rays. Of these,
the γ-rays are analogous to light, but of much higher frequencies,
or shorter wave-lengths; we need not further concern ourselves with
them. The α-rays and β-rays, on the contrary, are important as our
chief source of knowledge concerning the nuclei of atoms. It is found
that the α-rays consist of helium nuclei, while the β-rays consist
of electrons. Both come out of the nucleus, since the atom after
radio-activity disruption is a different element from what it was
before. But no one knows just why the nucleus disintegrates when it
does, nor why, in a piece of radium, for example, some atoms break down
while others do not.

The three principal sources of our knowledge concerning atoms have been
the light they emit, X-rays and radio-activity. As everyone knows,
when the light emitted by a glowing gas is passed through a prism, it
is found to consist of well-defined lines of different colours, which
are characteristic for each element, and constitute what is called its
“spectrum”. The spectrum extends beyond the range of visible light,
both into the infra-red and into the ultra-violet. In the latter
direction, it extends right into the region of X-rays, which are only
ultra-ultra-violet light. By means of crystals, it has been found
possible to study X-ray spectra as exactly as those of ordinary light.
The great merit of Bohr’s theory was that it explained why elements
have the spectra they do have, which had, before, been a complete
mystery. In the cases of hydrogen and positively electrified helium,
the explanation, particularly as extended by the German physicist
Sommerfeld, gave the most minute numerical agreement between theory
and observation; in other cases, mathematical difficulties made
this completeness impossible, but there was every reason to think
that the same principles were adequate. This was the main reason for
accepting Bohr’s theory; and certainly it was a very strong one. It
was found that visible light enabled us to study the outer rings of
planetary electrons, X-rays enabled us to study the inner rings,
and radio-activity enabled us to study the nucleus. For the latter
purpose, there are also other methods, more particularly Rutherford’s
“bombardment”, which aims at breaking up nuclei by firing projectiles
at them, and sometimes succeeds in making a hit in spite of the
smallness of the target.

The theory of atomic structure that has just been outlined, like
everything in theoretical physics, is capable of expression in
mathematical formulæ; but like many things in theoretical physics, it
is also capable of expression in the form of an imaginative picture.
But here, as always, it is necessary to distinguish sharply between
the mathematical symbols and the pictorial words. The symbols are
pretty sure to be right, or nearly so; the imaginative picture, on
the other hand, should not be taken too seriously. When we consider
the nature of the evidence upon which the above theory of the atom is
based, we can see that the attempt to make a picture of what goes on
has led us to be far more concrete than we have any right to be. If
we want to assert only what we have good reason to believe, we shall
have to abandon the attempt to be concrete about what goes on in the
atom, and say merely something like this: An atom with its electrons
is a system characterised by certain integers, all small, and all
capable of changing independently. These integers are the multiples of
_h_ involved. When any of them changes to a smaller integer, energy
of a definite amount is emitted, and its frequency will be obtained
by dividing the energy of _h_. When any of the integers concerned
changes to a larger integer, energy is absorbed, and again the amount
absorbed is definite. But we cannot know what goes on when the atom is
neither absorbing nor radiating energy, since then it has no effects in
surrounding regions; consequently all evidence as to atoms is as to
their changes, not as to their steady states.

The point is not that the facts do not fit with the hypothesis of
the atom as a planetary system. There are, it is true, certain
difficulties which afford empirical grounds for the newer theory which
has superseded Bohr’s, and which we shall shortly consider. But even
if no such grounds existed, it would be obvious that Bohr’s theory
states more than we have a right to infer from what we can observe. Of
theories that state so much, there must be an infinite number that are
compatible with what is known, and it is only what all of these have in
common that we are really entitled to assert. Suppose your knowledge
of Great Britain were entirely confined to observing the people and
goods that enter and leave the ports; you could, in that case, invent
many theories as to the interior of Great Britain, all of which would
agree with all known facts. This is an exact analogy. If you delimit
in the physical universe any region, large or small, not containing a
scientific observer, all scientific observers will have exactly the
same experiences whatever happens inside this region, provided it
does not affect the flow of energy across the boundary of the region.
And so, if the region contains one atom, any two theories which give
the same results as to the energy that the atom radiates or absorbs
are empirically indistinguishable, and there can be no reason except
simplicity for preferring one of them to the other. On this ground,
even if on no other, prudence compels us to seek a more abstract theory
of the atom than that which we owe to Rutherford and Bohr.

The newer theory has been put forward mainly by two physicists already
mentioned, Heisenberg and Schrödinger, in forms which look different,
but are in fact mathematically equivalent. It is as yet an impossible
task to describe this theory in simple language, but something can be
said to show its philosophical bearing. Broadly speaking, it describes
the atom by means of the radiations that come out of it. In Bohr’s
theory, the planetary electrons are supposed to describe orbits over
and over again while the atom is not radiating; in the newer theory,
we say nothing at all as to what happens at these times. The aim
is to confine the theory to what is empirically verifiable, namely
radiations; as to what there is where the radiations come from, we
cannot tell, and it is scientifically unnecessary to speculate. The
theory requires modifications in our conception of space, of a sort not
yet quite clear. It also has the consequence that we cannot identify an
electron at one time with an electron at another, if in the interval,
the atom has radiated energy. The electron ceases altogether to have
the properties of a “thing” as conceived by common sense; it is merely
a region from which energy may radiate.

On the subject of discontinuity, there is disagreement between
Schrödinger and other physicists. Most of them maintain that quantum
changes--_i.e._ the changes that occur in an atom when it radiates or
absorbs energy--must be discontinuous. Schrödinger thinks otherwise.
This is a matter in debate among experts, as to which it would be rash
to venture an opinion. Probably it will be decided one way or other
before very long.

The main point for the philosopher in the modern theory is the
disappearance of matter as a “thing”. It has been replaced by
emanations from a locality--the sort of influences that characterise
haunted rooms in ghost stories. As we shall see in the next chapter,
the theory of relativity leads to a similar destruction of the solidity
of matter, by a different line of argument. All sorts of events happen
in the physical world, but tables and chairs, the sun and moon,
and even our daily bread, have become pale abstractions, mere laws
exhibited in the successions of events which radiate from certain
regions.




CHAPTER X

RELATIVITY


We have seen that the world of the atom is a world of revolution rather
than evolution: the electron which has been moving in one orbit hops
quite suddenly into another, so that the motion is what is called
“discontinuous”, that is to say, the electron is first in one place and
then in another, without having passed over any intermediate places.
This sounds like magic, and there may be some way of avoiding such a
disconcerting hypothesis. At any rate, nothing of the sort seems to
happen in the regions where there are no electrons and protons. In
these regions, so far as we can discover, there is continuity, that
is to say, everything goes by gradual transitions, not by jumps. The
regions in which there are no electrons and protons may be called
“æther” or “empty space” as you prefer: the difference is only verbal.
The theory of relativity is especially concerned with what goes on in
these regions, as opposed to what goes on where there are electrons
and protons. Apart from the theory of relativity, what we know about
these regions is that waves travel across them, and that these waves,
when they are waves of light or electromagnetism (which are identical),
behave in a certain fashion set forth by Maxwell in certain formulæ
called “Maxwell’s equations”. When I say we “know” this, I am saying
more than is strictly correct, because all we know is what happens
when the waves reach our bodies. It is as if we could not see the sea,
but could only see the people disembarking at Dover, and inferred the
waves from the fact that the people looked green. It is obvious, in any
case, that we can only know so much about the waves as is involved in
their having such-and-such causes at one end and such-and-such effects
at the other. What can be inferred in this way will be, at best,
something wholly expressible in terms of mathematical structure. We
must not think of the waves as being necessarily “in” the æther or “in”
anything else; they are to be thought of merely as progressive periodic
processes, whose laws are more or less known, but whose intrinsic
character is not known and never can be.

The theory of relativity has arisen from the study of what goes on in
the regions where there are no electrons and protons. While the study
of the atom has led us to discontinuities, relativity has produced
a completely continuous theory of the intervening medium--far more
continuous than any theory formerly imagined. At the moment, these
two points of view stand more or less opposed to each other, but no
doubt before long they will be reconciled. There is not, even now, any
logical contradiction between them; there is only a fairly complete
lack of connection.

For philosophy, far the most important thing about the theory of
relativity is the abolition of the one cosmic time and the one
persistent space, and the substitution of space-time in place of both.
This is a change of quite enormous importance, because it alters
fundamentally our notion of the structure of the physical world, and
has, I think, repercussions in psychology. It would be useless, in our
day, to talk about philosophy without explaining this matter. Therefore
I shall make the attempt, in spite of some difficulty.

Common-sense and pre-relativity physicists believed that, if two events
happen in different places, there must always be a definite answer, in
theory, to the question whether they were simultaneous. This is found
to be a mistake. Let us suppose two persons A and B a long way apart,
each provided with a mirror and means of sending out light-signals. The
events that happen to A still have a perfectly definite time-order, and
so have those that happen to B; the difficulty comes in connecting A’s
time with B’s. Suppose A sends a flash to B, B’s mirror reflects it,
and it returns to A after a certain time. If A is on the earth and B
on the sun, the time will be about sixteen minutes. We shall naturally
say that the time when B received the light-signal is half way between
the times when A sent it out and received it back. But this definition
turns out to be not unambiguous; it will depend upon how A and B are
moving relatively to each other. The more this difficulty is examined,
the more insuperable it is seen to be. Anything that happens to A after
he sends out the flash and before he gets it back is neither definitely
before nor definitely after nor definitely simultaneous with the
arrival of the flash at B. To this extent, there is no unambiguous way
of correlating times in different places.

The notion of a “place” is also quite vague. Is London a “place”? But
the earth is rotating. Is the earth a “place”? But it is going round
the sun. Is the sun a “place”? But it is moving relatively to the
stars. At best you could talk of a place at a given time; but then it
is ambiguous what is a given time, unless you confine yourself to one
place. So the notion of “place” evaporates.

We naturally think of the universe as being in one state at one time
and in another at another. This is a mistake. There is no cosmic time,
and so we cannot speak of the state of the universe at a given time.
And similarly we cannot speak unambiguously of the distance between
two bodies at a given time. If we take the time appropriate to one of
the two bodies, we shall get one estimate; if the time of the other,
another. This makes the Newtonian law of gravitation ambiguous, and
shows that it needs restatement, independently of empirical evidence.

Geometry also goes wrong. A straight line, for example, is supposed to
be a certain track in space whose parts all exist simultaneously. We
shall now find that what is a straight line for one observer is not a
straight line for another. Therefore geometry ceases to be separable
from physics.

The “observer” need not be a mind, but may be a photographic plate.
The peculiarities of the “observer” in this region belong to physics,
not to psychology.

So long as we continue to think in terms of bodies moving, and try to
adjust this way of thinking to the new ideas by successive corrections,
we shall only get more and more confused. The only way to get clear is
to make a fresh start, with _events_ instead of bodies. In physics, an
“event” is anything which, according to the old notions, would be said
to have both a date and a place. An explosion, a flash of lightning,
the starting of a light-wave from an atom, the arrival of the
light-wave at some other body, any of these would be an “event”. Some
strings of events make up what we regard as the history of one body;
some make up the course of one light-wave; and so on. The unity of a
body is a unity of history--it is like the unity of a tune, which takes
time to play, and does not exist whole in any one moment. What exists
at any one moment is only what we call an “event”. It may be that the
word “event”, as used in physics, cannot be quite identified with the
same word as used in psychology; for the present we are concerned
with “events” as the constituents of physical processes, and need not
trouble ourselves about “events” in psychology.

The events in the physical world have relations to each other which
are of the sort that have led to the notions of space and time. They
have relations of order, so that we can say that one event is nearer
to a second than to a third. In this way we can arrive at the notion
of the “neighbourhood” of an event: it will consist roughly speaking
of all the events that are very near the given event. When we say that
neighbouring events have a certain relation, we shall mean that the
nearer two events are to each other, the more nearly they have this
relation, and that they approximate to having it without limit as they
are taken nearer and nearer together.

Two neighbouring events have a measurable quantitative relation
called “interval”, which is sometimes analogous to distance in space,
sometimes to lapse of time. In the former case it is called space-like,
in the latter time-like. The interval between two events is time-like
when one body might be present at both--for example, when both are
parts of the history of your body. The interval is space-like in the
contrary case. In the marginal case between the two, the interval is
zero; this happens when both are parts of one light-ray.

The interval between two neighbouring events is something objective,
in the sense that any two careful observers will arrive at the same
estimate of it. They will not arrive at the same estimate for the
distance in space or the lapse of time between the two events, but the
interval is a genuine physical fact, the same for all. If a body can
travel freely from one event to the other, the interval between the two
events will be the same as the time between them as measured by a clock
travelling with the body. If such a journey is physically impossible,
the interval will be the same as the distance as estimated by an
observer to whom the two events are simultaneous. But the interval is
only definite when the two events are very near together; otherwise
the interval depends upon the route chosen for travelling from the one
event to the other.

Four numbers are needed to fix the position of an event in the world;
these correspond to the time and the three dimensions of space in the
old reckoning. These four numbers are called the co-ordinates of the
event. They may be assigned on any principle which gives neighbouring
co-ordinates to neighbouring events; subject to this condition, they
are merely conventional. For example, suppose an aeroplane has had an
accident. You can fix the position of the accident by four numbers:
latitude, longitude, altitude above sea-level, and Greenwich Mean Time.
But you cannot fix the position of the explosion in space-time by means
of less than four numbers.

Everything in relativity-theory goes (in a sense) from next to
next; there are no direct relations between distant events, such as
distance in time or space. And of course there are no forces acting
at a distance; in fact, except as a convenient fiction, there are
no “forces” at all. Bodies take the course which is easiest at each
moment, according to the character of space-time in the particular
region where they are; this course is called a _geodesic_.

Now it will be observed that I have been speaking freely of bodies and
motion, although I said that bodies were merely certain strings of
events. That being so, it is of course necessary to say what strings of
events constitute bodies, since not all continuous strings of events
do so, not even all geodesics. Until we have defined the sort of thing
that makes a body, we cannot legitimately speak of motion, since this
involves the presence of one body on different occasions. We must
therefore set to work to define what we mean by the persistence of a
body, and how a string of events constituting a body differs from one
which does not. This topic will occupy the next chapter.

But it may be useful, as a preliminary, to teach our imagination to
work in accordance with the new ideas. We must give up what Whitehead
admirably calls the “pushiness” of matter. We naturally think of an
atom as being like a billiard-ball; we should do better to think of it
as like a ghost, which has no “pushiness” and yet can make you fly. We
have to change our notions both of substance and of cause. To say that
an atom persists is like saying that a tune persists. If a tune takes
five minutes to play, we do not conceive of it as a single thing which
exists throughout that time, but as a series of notes, so related as
to form a unity. In the case of the tune, the unity is æsthetic; in
the case of the atom, it is causal. But when I say “causal” I do not
mean exactly what the word naturally conveys. There must be no idea of
compulsion or “force”, neither the force of contact which we imagine
we see between billiard-balls nor the action at a distance which
was formerly supposed to constitute gravitation. There is merely an
observed law of succession from next to next. An event at one moment
is succeeded by an event at a neighbouring moment, which, to the first
order of small quantities, can be calculated from the earlier event.
This enables us to construct a string of events, each, approximately,
growing out of a slightly earlier event according to an intrinsic law.
Outside influences only affect the second order of small quantities. A
string of events connected, in this way, by an approximate intrinsic
law of development is called one piece of matter. This is what I mean
by saying that the unity of a piece of matter is causal. I shall
explain this notion more fully in later chapters.




CHAPTER XI

CAUSAL LAWS IN PHYSICS


In the last chapter we spoke about the substitution of space-time for
space and time, and the effect which this has had in substituting
strings of events for “things” conceived as substances. In this chapter
we will deal with cause and effect as they appear in the light of
modern science. It is at least as difficult to purge our imagination
of irrelevances in this matter as in regard to substance. The
old-fashioned notion of cause appeared in dynamics as “force”. We still
speak of forces just as we still speak of the sunrise, but we recognise
that this is nothing but a convenient way of speaking, in the one case
as in the other.

Causation is deeply embedded in language and common sense. We say that
people build houses or make roads: to “build” and to “make” are both
notions involving causality. We say that a man is “powerful”, meaning
that his volitions are causes over a wide range. Some examples of
causation seem to us quite natural, others less so. It seems natural
that our muscles should obey our will, and only reflection makes us
perceive the necessity of finding an explanation of this phenomenon. It
seems natural that when you hit a billiard-ball with a cue it moves.
When we see a horse pulling a cart, or a heavy object being dragged by
a rope, we _feel_ as if we understood all about it. It is events of
this sort that have given rise to the common-sense belief in causes and
forces.

But as a matter of fact the world is incredibly more complicated than
it seems to common sense. When we think we understand a process--I mean
by “we” the non-reflective part in each of us--what really happens
is that there is some sequence of events so familiar through past
experience that at each stage we expect the next stage. The whole
process seems to us peculiarly intelligible when human desires enter
in, for example, in watching a game: what the ball does and what the
players do seem “natural”, and we feel as if we quite understood how
the stages succeed each other. We thus arrive at the notion of what is
called “necessary” sequence. The text-books say that A is the cause of
B if A is “necessarily” followed by B. This notion of “necessity” seems
to be purely anthropomorphic, and not based upon anything that is a
discoverable feature of the world. Things happen according to certain
rules; the rules can be generalised, but in the end remain brute facts.
Unless the rules are concealed conventions or definitions, no reason
can be given why they should not be completely different.

To say that A is “necessarily” followed by B is thus to say no more
than that there is some general rule, exemplified in a very large
number of observed instances, and falsified in none, according to which
events such as A are followed by events such as B. We must not have any
notion of “compulsion”, as if the cause _forced_ the effect to happen.
A good test for the imagination in this respect is the reversibility
of causal laws. We can just as often infer backwards as forwards.
When you get a letter, you are justified in inferring that somebody
wrote it, but you do not feel that your receiving it _compelled_
the sender to write it. The notion of compulsion is just as little
applicable to effects as to causes. To say that causes compel effects
is as misleading as to say that effects compel causes. Compulsion is
anthropomorphic: a man is compelled to do something when he wishes to
do the opposite, but except where human or animal wishes come in the
notion of compulsion is inapplicable. Science is concerned merely with
what happens, not with what _must_ happen.

When we look for invariable rules of sequence in nature, we find that
they are not such as common sense sets up. Common sense says: thunder
follows lightning, waves at sea follow wind, and so on. Rules of
this sort are indispensable in practical life, but in science they
are all only approximate. If there is any finite interval of time,
however short, between the cause and the effect, something may happen
to prevent the effect from occurring. Scientific laws can only be
expressed in differential equations. This means that, although you
cannot tell what may happen after a finite time, you can say that, if
you make the time shorter and shorter, what will happen will be more
and more nearly according to such-and-such a rule. To take a very
simple case: I am now in this room; you cannot tell where I shall be
in another second, because a bomb may explode and blow me sky-high,
but if you take any two small fragments of my body which are now very
close together, you can be sure that, after _some_ very short finite
time, they will still be very close together. If a second is not short
enough, you must take a shorter time; you cannot tell in advance how
short a time you may have to take, but you may feel fairly certain that
there is a short enough time.

The laws of sequence in physics, apart from quantum phenomena, are of
two sorts, which appeared in traditional dynamics as laws of velocity
and laws of acceleration. In a very short time, the velocity of a
body alters very little, and if the time is taken short enough, the
change of velocity diminishes without limit. This is what, in the last
chapter, we called an “intrinsic” causal law. Then there is the effect
of the outer world, as it appeared in traditional dynamics, which
is shown in acceleration. The small change which does occur in the
velocity in a short time is attributed to surrounding bodies, because
it is found to vary as they vary, and to vary according to ascertained
laws. Thus we think of surrounding bodies as exerting an influence,
which we call “force”, though this remains as mysterious as the
influence of the stars in astrology.

Einstein’s theory of gravitation has done away with this conception in
so far as gravitational forces are concerned. In this theory, a planet
moving round the sun is moving in the nearest approach to a straight
line that the neighbourhood permits. The neighbourhood is supposed to
be non-Euclidean, that is to say, to contain no straight lines such
as Euclid imagined. If a body is moving freely, as the planets do, it
observes a certain rule. Perhaps the simplest way to state this rule
is as follows: Suppose you take any two events which happen on the
earth, and you measure the time between them by ideally accurate clocks
which move with the earth. Suppose some traveller on a magic carpet had
meanwhile cruised about the universe, leaving the earth at the time of
the first event and returning at the time of the second. By his clocks
the period elapsed will be less than by the terrestial clocks. This is
what is meant by saying that the earth moves in a “geodesic”, which
is the nearest approach to a straight line to be found in the region
in which we live. All this is, so to speak, geometrical, and involves
no “forces”. It is not the sun that makes the earth go round, but the
nature of space-time where the earth is.

Even this is not quite correct. Space-time does not make the earth go
round the sun; it makes us _say_ the earth goes round the sun. That is
to say, it makes this the shortest way of describing what occurs. We
could describe it in other language, which would be equally correct,
but less convenient.

The abolition of “force” in astronomy is perhaps connected with the
fact that astronomy depends only upon the sense of sight. On the
earth, we push and pull, we touch things, and we experience muscular
strains. This all gives us a notion of “force”, but this notion is
anthropomorphic. To imagine the laws of motion of heavenly bodies,
think of the motions of objects in a mirror; they may move very fast,
although in the mirror world there are no forces.

What we really have to substitute for force is laws of correlation.
Events can be collected in groups by their correlations. This is
all that is true in the old notion of causality. And this is not a
“postulate” or “category”, but an observed fact--lucky, not necessary.

As we suggested before, it is these correlations of events that lead
to the definition of permanent “things”. There is no essential
difference, as regards substantiality, between an electron and a
light-ray. Each is really a string of events or of sets of events. In
the case of the light-ray, we have no temptation to think otherwise.
But in the case of the electron, we think of it as a single persistent
entity. There _may_ be such an entity, but we can have no evidence that
there is. What we can discover is (_a_) a group of events spreading
outwards from a centre--say, for definiteness, the events constituting
a wave of light--and attributed, hypothetically, to a “cause” in that
centre; (_b_) more or less similar groups of events at other times,
connected with the first group according to the laws of physics, and
therefore attributed to the same hypothetical cause at other times. But
all that we ought to assume is series of groups of events, connected by
discoverable laws. These series we may _define_ as “matter”. Whether
there is matter in any other sense, no one can tell.

What is true in the old notion of causality is the fact that events at
different times are connected by laws (differential equations). When
there is a law connecting an event A with an event B, the two have a
definite unambiguous time-order. But if the events are such that a ray
of light starting from A would arrive at any body which was present at
B after B had occurred, and _vice versa_, then there is no definite
true order, and no possible causal law connecting A and B. A and B must
then be regarded as separate facts of geography.

Perhaps the scope and purpose of this and the foregoing chapters may
be made clearer by showing their bearing upon certain popular beliefs
which may seem self-evident but are really in my opinion either false
or likely to lead to falsehood. I shall confine myself to objections
which have actually been made to me when trying to explain the
philosophical outcome of modern physics.[8]

      [8] These objections are quoted (with kind permission) from a
          letter written to me by a well-known engineer, Mr. Percy
          Griffith, who is also a writer on philosophical subjects.

“We cannot conceive of movement apart from some _thing_ as moving.”
This is, in a sense, a truism; but in the sense in which it is usually
meant, it is a falsehood. We speak of the “movement” of a drama or
piece of music, although we do not conceive either as a “thing” which
exists complete at every moment of the performance. This is the sort of
picture we must have in our minds when we try to conceive the physical
world. We must think of a string of events, connected together by
certain causal connections, and having enough unity to deserve a single
name. We then begin to imagine that the single name denotes a single
“thing”, and if the events concerned are not all in the same place, we
say the “thing” has “moved.” But this is only a convenient shorthand.
In the cinema, we seem to see a man falling off a skyscraper, catching
hold of the telegraph wires, and reaching the ground none the worse.
We know that, in fact, there are a number of different photographs,
and the appearance of a single “thing” moving is deceptive. In this
respect, the real world resembles the cinema.

In connection with motion one needs to emphasise the very difficult
distinction between _experience_ and _prejudice_. Experience, roughly,
is what you see, and prejudice is what you only think you see.
Prejudice tells you that you see the _same_ table on two different
occasions; you _think_ that experience tells you this. If it really
were experience, you could not be mistaken; yet a similar table may be
substituted without altering the experience. If you look at a table
on two different occasions, you have very similar sensations, and
memory tells you that they are similar; but there is nothing to show
that one identical entity causes the two sensations. If the table is
in a cinema, you know that there is not such an entity, even though
you can watch it changing with apparent continuity. The experience is
just like that with a “real” table; so in the case of a “real” table
also, there is nothing in the actual experience to show whether there
is a persistent entity or not. I say, therefore: I do not know whether
there is a persistent entity, but I do know that my experiences can be
explained without assuming that there is. Therefore it can be no part
of legitimate science to assert or deny the persistent entity; if it
does either, it goes beyond the warrant of experience.

The following is a verbally cited passage in the letter referred to
objecting to what was said above about “force”:

“The concept of Force is not of physical but of psychological origin.
Rightly or wrongly it arises in the most impersonal contemplation of
the Stellar Universe, where we observe an infinite number of spherical
bodies revolving on their own axes and gyrating in orbits round each
other. Rightly or wrongly, we naturally conceive of these as having
been so constituted and so maintained by some Force or Forces.”

We do not, in fact, “observe” what it is here said that we observe; all
this is _inferred_. What we observe, in astronomy, is a two-dimensional
pattern of points of light, with a few bright surfaces of measurable
size when seen through the telescope (the planets), and of course
the larger bright surfaces that we call the sun and moon. Most of
this pattern (the fixed stars) rotates round the earth once in every
twenty-three hours and fifty-six minutes. The sun rotates in varying
periods, which average twenty-four hours and never departs very far
from the average. The moon and planets have apparent motions which are
more irregular. These are the _observed_ facts. There is no logical
impossibility about the formulæ doctrine of spheres rotating round the
earth, one for each planet and one for the stars. The modern doctrines
are simpler, but not one whit more in accordance with observed facts;
it is our passion for _simple_ laws that has made us adopt them.

The last sentence of the above quotation raises some further points of
interest. “Rightly or wrongly”, the writer says, “we naturally conceive
of these as having been so constituted and so maintained by some Force
or Forces.” I do not deny this. It is “natural”, and it is “right or
wrong”--more specifically, it is wrong. “Force” is part of our love of
explanations. Everyone knows about the Hindu who thought that the world
does not fall because it is supported by an elephant, and the elephant
does not fall because it is supported by a tortoise. When his European
interlocutor said “But how about the tortoise?” he replied that he was
tired of metaphysics and wanted to change the subject. “Force”, as an
explanation, is no better than the elephant and the tortoise. It is
an attempt to get at the “why” of natural processes, not only at the
“how”. What we observe, to a limited extent, is what happens, and we
can arrive at laws according to which observable things happen, but
we cannot arrive at a reason for the laws. If we invent a reason, it
needs a reason in its turn, and so on. “Force” is a rationalising of
natural processes, but a fruitless one since “force” would have to be
rationalised also.

When it is said, as it often is, that “force” belongs to the world of
experience, we must be careful to understand what can be meant. In
the first place, it may be meant that calculations which employ the
notion of force work out right in practice. This, broadly speaking,
is admitted: no one would suggest that the engineer should alter his
methods, or should give up working out stresses and strains. But that
does not prove that there are stresses and strains. A British medical
man renders his accounts in guineas, although they have long since
ceased to exist except as a name; he obtains a real payment, though he
employs a fictitious coin. Similarly, the engineer is concerned with
the question whether his bridge will stand: the fact of experience is
that it stands (or does not stand), and the stresses and strains are
only a way of explaining what sort of bridge will stand. They are as
useful as guineas, but equally imaginary.

But when it is said that force is a fact of experience, there is
something quite different that may be meant. It may be meant that we
experience force when we experience such things as pressure or muscular
exertion. We cannot discuss this contention adequately without going
into the relation of physics to psychology, which is a topic we shall
consider at length at a later stage. But we may say this much: if
you press your finger-tip upon a hard object, you have an experience
which you attribute to your finger-tip, but there is a long chain of
intermediate causes in nerves and brain. If your finger were amputated
you could still have the same experience by a suitable operation on
the nerves that formerly connected the finger with the brain, so that
the force between the finger-tip and the hard object, as a fact of
experience, may exist when there is no finger-tip. This shows that
force, in this sense, cannot be what concerns physics.

As the above example illustrates, we do not, in fact, experience
many things that we think we experience. This makes it necessary to
ask, without too much assurance, in what sense physics can be based
upon experience, and what must be the nature of its entities and its
inferences if it is to make good its claim to be empirically grounded.
We shall begin this inquiry in the next chapter.




CHAPTER XII

PHYSICS AND PERCEPTION


It will be remembered that we regarded perception, in Chapter V, as
a species of “sensitivity”. Sensitivity to a given feature of the
environment we defined as consisting in some characteristic reaction
which is exhibited whenever that feature is present, but not otherwise;
this property is possessed more perfectly, in given directions, by
scientific instruments than by living bodies, though scientific
instruments are more selective as to the stimuli to which they will
respond. We decided that what, from the standpoint of an external
observer, distinguishes perception from other forms of sensitivity is
the law of association or conditioned reflexes. But we also found that
this purely external treatment of perception presupposes our knowledge
of the physical world as a going concern. We have now to investigate
this presupposition, and to consider how we come to know about physics,
and how much we really do know.

According to the theory of Chapter V, it is possible to perceive things
that are not in a spatial contact with the body. There must be a
reaction to a feature of the environment, but that feature may be at a
greater or less distance from the body of the percipient; we can even
perceive the sun and stars, within the limits of the definition. All
that is necessary is that our reaction should depend upon the spatial
relation between our body and the feature of the environment. When our
back is towards the sun, we do not see it; when our face is towards it,
we do.

When we consider perception--visual or auditory--of an external event,
there are three different matters to be examined. There is first the
process in the outside world, from the event to the percipient’s body;
there is next the process in his body, in so far as this can be known
by an outside observer; lastly, there is the question, which must be
faced sooner or later, whether the percipient can perceive something of
the process in his body which no other observer could perceive. We will
take these points in order.

If it is to be possible to “perceive” an event not in the percipient’s
body, there must be a physical process in the outer world such that,
when a certain event occurs, it produces a stimulus of a certain kind
at the surface of the percipient’s body. Suppose, for example, that
pictures of different animals are exhibited on a magic lantern to a
class of children, and all the children are asked to say the name of
each animal in turn. We may assume that the children are sufficiently
familiar with animals to say “cat”, “dog”, “giraffe”, “hippopotamus”,
etc., at the right moments. We must then suppose--taking the physical
world for granted--that some process travels from each picture to the
eyes of the various children, retaining throughout these journeys such
peculiarities that, when the process reaches their eyes, it can in one
case stimulate the word “cat” and in another the word “dog”. All this
the physical theory of light provides for. But there is one interesting
point about language that should be noticed in this connection. If the
usual physical theory of light is correct, the various children will
receive stimuli which differ greatly according to their distance and
direction from the picture, and according to the way the light falls.
There are also differences in their reactions, for, though they all
utter the word “cat”, some say it loud, others soft, some in a soprano
voice, some in a contralto. But the differences in their reactions are
much less than the differences in the stimuli. This is still more the
case if we consider various different pictures of cats, to all of which
they respond with the word “cat”. Thus language is a means of producing
responses which differ less than the stimuli do, in cases where the
resemblances between the stimuli are more important to us than the
differences. This fact makes us apt to overlook the differences
between stimuli which produce nearly identical responses.

As appears from the above, when a number of people simultaneously
perceive a picture of a cat, there are differences between the stimuli
to their various perceptions, and these differences must obviously
involve differences in their reactions. The _verbal_ responses may
differ very little, but even the verbal responses could be made to
differ by putting more complicated questions than merely “What animal
is that?” One could ask: “Can the picture be covered by your thumb-nail
held at arm’s length?” Then the answer would be different according
as the percipient was near the picture or far off. But the normal
percipient, if left to himself, will not notice such differences,
that is to say, his verbal response will be the same in spite of the
differences in the stimuli.

The fact that it is possible for a number of people to perceive the
same noise or the same coloured pattern obviously depends upon the fact
that a physical process can travel outward from a centre and retain
certain of its characteristics unchanged, or very little changed. The
most notable of such characteristics is frequency in a wave-motion.
That, no doubt, affords a biological reason for the fact that our most
delicate senses, sight and hearing, are sensitive to frequencies, which
determine colour in what we see and pitch in what we hear. If there
were not, in the physical world, processes spreading out from centres
and retaining certain characters practically unchanged, it would be
impossible for different percipients to perceive the same object from
different points of view, and we should not have been able to discover
that we all live in a common world.

We come now to the process in the percipient’s body, in so far as
this can be perceived by an outside observer. This raises no new
philosophical problems, because we are still concerned, as before, with
the perception of events outside the observer’s body. The observer,
now, is supposed to be a physiologist, observing, say, what goes on
in the eye when light falls upon it. His means of knowing are, in
principle, exactly the same as in the observation of dead matter.
An event in an eye upon which light is falling causes light-waves
to travel in a certain manner until they reach the eye of the
physiologist. They there cause a process in the physiologist’s eye
and optic nerve and brain, which ends in what he calls “seeing what
happens in the eye he is observing”. But this event, which happens in
the physiologist, is not what happened in the eye he was observing;
it is only connected with this by a complicated causal chain. Thus
our knowledge of physiology is no more direct or intimate than our
knowledge of processes in dead matter; we do not know any more about
our eyes than about the trees and fields and clouds that we see by
means of them. The event which happens when a physiologist observes an
eye is an event in him, not on the eye that he is observing.

We come now at last to the question of self-observation, which we have
hitherto avoided. I say “self-observation” rather than “introspection”,
because the latter word has controversial associations that I wish to
avoid. I mean by “self-observation” anything that a man can perceive
about himself but that others, however situated, cannot perceive about
him. What follows is only preliminary, since the subject will be
discussed at length in Chapter XVI.

No one can deny that we know things about ourselves which others
cannot know unless we tell them. We know when we have toothache, when
we feel thirsty, what we were dreaming when we woke up, and so on.
Dr. Watson might say that the dentist can know we have toothache by
observing a cavity in a tooth. I will not reply that the dentist is
often mistaken; this may be merely because the art of dentistry has not
been sufficiently perfected. I will concede as possible, in the future,
a state of odontology in which the dentist could always know whether
I am feeling toothache. But even then his knowledge has a different
character from mine. His knowledge is an inference, based upon the
inducive law that people with such-and-such cavities suffer pain of
a certain kind. But this law cannot be established by observation of
cavities alone; it requires that, where these are observed, the people
who have them should tell us that they feel toothache. And, more than
that, they must be speaking the truth. Purely external observation can
discover that people with cavities _say_ they have toothache, but not
that they have it. Saying one has toothache is a different thing from
having it; if not we could cure toothache by not talking about it, and
so save our dentists’ bills. I am sure the expert opinion of dentists
will agree with me that this is impossible.

To this argument, however, it might be replied that having toothache is
a state of the body, and that knowing I have toothache is a response to
this bodily stimulus. It will be said that, theoretically, the state
of my body when I have toothache can be observed by an outsider, who
can then also know that I have toothache. This answer, however, does
not really meet the point. When the outside observer knows that I have
toothache, not only is his knowledge based upon an inductive inference,
as we have already seen, but his knowledge of the inferred term,
“toothache”, must be based upon personal experience. No knowledge of
dentistry could enable a man to know what toothache is if he had never
felt it. If, then, toothache is really a state of the body--which, at
the moment, I neither affirm nor deny--it is a state of the body which
only the man himself can perceive. In a word, whoever has experienced
toothache and can remember it has knowledge that cannot be possessed by
a man who has never experienced toothache.

Take next our knowledge of our own dreams. Dr. Watson has not, so far
as I know, ever discussed dreams, but I imagine he would say something
like this: In dreams, there are probably small laryngeal movements
such as, if they were greater, would lead to speech; indeed, people
do sometimes cry out in dreams. There may also be stimulations of the
sense-organs, which produce unusual reactions owing to the peculiar
physiological condition of the brain during sleep: but all these
reactions must consist of small movements, which could theoretically be
seen from outside, say by some elaboration of X-ray apparatus. This is
all very well, but meantime it is hypothetical, and the dreamer himself
knows his dreams without all this elaborate inference. Can we say that
he really knows these hypothetical small bodily movements, although
he thinks he knows something else? That would presumably be Dr.
Watson’s position, and it must be admitted that, with a definition of
“knowledge” such as we considered in Chapter VIII, such a view is not
to be dismissed offhand as obviously impossible. Moreover, if we are to
say the perception gives knowledge of the physical world, we shall have
to admit that what we are perceiving may be quite different from what
it seems to be. A table does not look like a vast number of electrons
and protons, nor like trains of waves meeting and clashing. Yet this
is the sort of thing a table is said to be by modern physicists. If,
then, what seems to us to be just a table such as may be seen any day
is really this odd sort of thing, it is possible that what seems to us
to be a dream is really a number of movements in the brain.

This again is all very well, but there is one point which it fails to
explain, namely, what is meant by “seeming”. If a dream or a table
“seems” to be one sort of thing while it is “really” another, we shall
have to admit that it _really_ seems, and that what it seems to be has
a reality of its own. Nay more, we only arrive at what it “really” is
by an inference, valid or invalid, from what it seems to be. If we are
wrong about the seeming, we must be doubly wrong about the reality,
since the sole ground for asserting the table composed of electrons and
protons is the table that we see, _i.e._ the “seeming” table. We must
therefore treat “seeming” with respect.

Let us consider Dr. Watson watching a rat in a maze. He means to be
quite objective, and report only what really goes on. Can he succeed?
In one sense he can. He can use words about what he sees which are
the same as any other scientifically trained observer will use if he
watches the same rat at the same time. But Dr. Watson’s objectivity
emphatically does not consist in using the same words as other people
use; his vocabulary is very different from that of most psychologists.
He cannot take as the sole test of truth the consensus of mankind.
“Securus judicat orbis terrarum” is another example of a Latin tag
which is false, and which certainly Dr. Watson would not consider
true. It has happened again and again in human history that a man who
said something that had never been said before turned out to be right,
while the people who repeated the wise saws of their forefathers were
talking nonsense. Therefore, when Dr. Watson endeavours to eliminate
subjectivity in observing rats, he does not mean that he says what
everybody else says. He means that he refrains from inferring anything
about the rat beyond its bodily movements. This is all to the good,
but I think he fails to realise that almost as long and difficult
an inference is required to give us knowledge of the rat’s bodily
movements as to give us knowledge of its “mind”. And what is more,
the data from which we must start in order to get to know the rat’s
bodily movements are data of just the sort that Dr. Watson wishes to
avoid, namely private data patent to self-observation but not patent to
anyone except the observer. This is the point at which, in my opinion,
behaviourism _as a final philosophy_ breaks down.

When several people simultaneously watch a rat in a maze, or any other
example of what we should naturally regard as matter in motion, there
is by no means complete identity between the physical events which
happen at the surface of their eyes and constitute the stimuli to
their perceptions. There are differences of perspective, of light and
shade, of apparent size, and so on, all of which will be reproduced
in photographs taken from the places where the eyes of the several
observers are. These differences produce differences in the reactions
of the observers--differences which a quite unthinking person may
overlook, but which are familiar to every artist. Now it is contrary
to all scientific canons to suppose that the object perceived, in
addition to affecting us in the way of stimulus and reaction, also
affects us directly by some mystical epiphany; certainly it is not what
any behaviourist would care to assert. Our knowledge of the physical
world, therefore, must be contained in our reaction to the stimulus
which reaches us across the intervening medium; and it seems hardly
possible that our reaction should have a more intimate relation to the
object than the stimulus has. Since the stimulus differs for different
observers, the reaction also differs; consequently, in all our
perceptions of physical processes there is an element of subjectivity.
If, therefore, physics is true in its broad outlines (as the above
argument supposes), what we call “perceiving” a physical process is
something private and subjective, at least in part, and is yet the only
possible starting-point for our knowledge of the physical world.

There is an objection to the above argument which might naturally be
made, but it would be in fact invalid. It may be said that we do not in
fact proceed to _infer_ the physical world from our perceptions, but
that we begin at once with a rough-and-ready knowledge of the physical
world, and only at a late stage of sophistication compel ourselves to
regard our knowledge of the physical world as an inference. What is
valid in this statement is the fact that our knowledge of the physical
world is not at first inferential, but that is only because we take our
percepts to _be_ the physical world. Sophistication and philosophy come
in at the stage at which we realise that the physical world cannot be
identified with our percepts. When my boy was three years old, I showed
him Jupiter, and told him that Jupiter was larger than the earth. He
insisted that I must be speaking of some other Jupiter, because, as he
patiently explained, the one he was seeing was obviously quite small.
After some efforts, I had to give it up and leave him unconvinced. In
the case of the heavenly bodies, adults have got used to the idea that
what is really there can only be _inferred_ from what they see; but
where rats in mazes are concerned, they still tend to think that they
are seeing what is happening in the physical world. The difference,
however, is only one of degree, and naive realism is as untenable in
the one case as in the other. There are differences in the perceptions
of two persons observing the same process; there are sometimes no
discoverable differences between two perceptions of the same persons
observing different processes, _e.g._ pure water and water full of
bacilli. The subjectivity of our perceptions is thus of practical as
well as theoretical importance.

I am not maintaining that what we primarily know is our own
perceptions. This is largely a verbal question; but with the definition
of knowledge given in Chapter VIII, it will be correct to say that
from the first we know external objects, the question is not as to
what are the objects we know, but rather as to how accurately we
know them. Our non-inferential knowledge of an object cannot be more
accurate than our reaction to it, since it is part of that reaction.
And our reaction cannot be more accurate than the stimulus. But what
on earth can you mean by the “accuracy” of a stimulus? I may be
asked. I mean just the same as by the accuracy of a map or a set of
statistics. I mean a certain kind of correspondence. One pattern is
an accurate representation of another if every element of the one can
be taken as the representative of just one element of the other, and
the relations that make the one set into a pattern correspond with
relations making the other set into a pattern. In this sense, writing
can represent speech with a certain degree of accuracy; to every spoken
word a written word corresponds, and to the time-order of the spoken
words the space-order of the written words corresponds. But there are
inflexions and tones of voice that cannot be represented in writing,
except, to some extent, by musical notation. A gramophone record is
a much more accurate representation of vocal sounds than any writing
can be; but even the best gramophone record fails to be completely
accurate. The impression made upon an observer is very analogous to
a gramophone record or a photograph, but usually less accurate owing
to the influence of the law of association, and the lack of delicacy
in our senses. And whatever limitations there are to the accuracy of
our impressions are limitations to the accuracy of our non-inferential
knowledge of the external world.

Another point: If we accept the definition of knowledge given
in Chapter VIII, which was framed so far as to be as favourable
as possible to behaviourism, a given reaction may be regarded as
knowledge of various different occurrences. When we see Jupiter, we
have, according to the definition, knowledge of Jupiter, but we also
have knowledge of the stimulus at the surface of the eye, and even
of the process in the optic nerve. For it is arbitrary at what point
we start in the process leading to a certain event in the brain:
this event, and the consequent bodily action, may be regarded as a
reaction to a process starting at any earlier point. And the nearer
our starting-point is to the brain, the more accurate becomes the
knowledge displayed in our reaction. A lamp at the top of a tall
building might produce the same visual stimulus as Jupiter, or at any
rate one practically indistinguishable from that produced by Jupiter.
A blow on the nose might make us “see stars”. Theoretically, it should
be possible to apply a stimulus direct to the optic nerve, which
should give us a visual sensation. Thus when we think we see Jupiter,
we may be mistaken. We are less likely to be mistaken if we say that
the surface of the eye is being stimulated in a certain way, and still
less likely to be mistaken if we say that the optic nerve is being
stimulated in a certain way. We do not eliminate the risk of error
completely unless we confine ourselves to saying that an event of a
certain sort is happening in the brain; this statement may still be
true if we see Jupiter in a dream.

But, I shall be asked, what do you know about what is happening in the
brain? Surely nothing. Not so, I reply. I know about what is happening
in the brain exactly what naive realism thinks it knows about what is
happening in the outside world. But this needs explaining, and there
are other matters that must be explained first.

When the light from a fixed star reaches me, I see the star if it is
night and I am looking in the right direction. The light started years
ago, probably many years ago, but my reaction is primarily to something
that is happening _now_. When my eyes are open, I see the star; when
they are shut, I do not. Children discover at a fairly early age
that they see nothing when their eyes are shut. They are aware of the
difference between seeing and not seeing, and also of the difference
between eyes open and eyes shut; gradually they discover that these
two differences are correlated--I mean that they have expectations of
which this is the intellectualist transcription. Again, children learn
to name the colours, and to state correctly whether a thing is blue
or red or yellow or what-not. They ought not to be sure that light of
the appropriate wave-length started from the object. The sun looks red
in a London fog, grass looks blue through blue spectacles, everything
looks yellow to a person suffering from jaundice. But suppose you ask:
What colour are you seeing? The person who answers, in these cases,
red for the sun, blue for the grass, and yellow for the sick-room of
the jaundiced patient, is answering quite truly. And in each of these
cases he is stating something that he _knows_. What he knows in such
cases is what I call a “percept”. I shall contend later that, from the
standpoint of physics, a percept is in the brain; for the present, I am
only concerned to say that a percept is what is most indubitable in our
knowledge of the world.

To behaviourism as a metaphysic one may put the following dilemma.
Either physics is valid in its main lines, or it is not. If it is
not, we know nothing about the movements of matter; for physics is
the result of the most serious and careful study of which the human
intelligence has hitherto been capable. If, on the other hand, physics
is valid in its main lines, any physical process starting either inside
or outside the body will, if it reaches the brain, be different if
the intervening medium is different; moreover two persons, initially
very different, may become indistinguishable as they spread and grow
fainter. On both grounds, what happens in the brain is not connected
quite accurately with what happens elsewhere, and our perceptions
are therefore infected with subjectivity on purely physical grounds.
Even, therefore, when we assume the truth of physics, what we know
most indubitably through perception is not the movements of matter,
but certain events in ourselves which are connected, in a manner not
quite invariable, with the movements of matter. To be specific, when
Dr. Watson watches rats in mazes, what he knows, apart from difficult
inferences, are certain events in himself. The behaviour of the rats
can only be inferred by the help of physics, and is by no means to be
accepted as something accurately knowable by direct observation.

I do not in fact entertain any doubts that physics is true in its main
lines. The interpretation of physical formulæ is a matter as to which
a considerable degree of uncertainty is possible; but we cannot well
doubt that there is an interpretation which is true roughly and in
the main. I shall come to the question of interpretation later; for
the present, I shall assume that we may accept physics in its broad
outlines, without troubling to consider how it is to be interpreted.
On this basis, the above remarks on perception seem undeniable. We
are often misled as to what is happening, either by peculiarities of
the medium between the object and our bodies, or by unusual states of
our bodies, or by a temporary or permanent abnormality in the brain.
But in all these cases _something_ is really happening, as to which,
if we turn our attention to it, we can obtain knowledge that is not
misleading. At one time when, owing to illness, I had been taking a
great deal of quinine, I became hypersensitive to noise, so that when
the nurse rustled the newspaper I thought she was spilling a scuttle
of coals on the floor. The interpretation was mistaken, but it was
quite true that I heard a loud noise. It is a commonplace that a man
whose leg has been amputated can still feel pains in it; here again,
he does really feel the pains, and is only mistaken in his belief that
they come from his leg. A percept is an observable event, but its
interpretation as knowledge of this or that event in the physical world
is liable to be mistaken, for reasons which physics and physiology can
make fairly clear.

The subjectivity of percepts is a matter of degree. They are more
subjective when people are drunk or asleep than when they are sober
and awake. They are more subjective in regard to distant objects than
in regard to such as are near. They may acquire various peculiar kinds
of subjectivity through injuries to the brain or to the nerves. When
I speak of a percept as “subjective” I mean that the physiological
inferences to which it gives rise are mistaken or vague. This is
always the case to some extent, but much more so in some circumstances
than in others. And the sort of defect that leads to mistakes must be
distinguished from the sort that leads to vagueness. If you see a man a
quarter of a mile away, you can see that it is a man if you have normal
eyesight, but you probably cannot tell who it is, even if in fact
it is some one you know well. This is vagueness in the percept: the
inferences you draw are correct so far as they go, but they do not go
very far. On the other hand, if you are seeing double and think there
are two men, you have a case of mistake. Vagueness, to a greater or
less extent, is universal and inevitable; mistakes, on the other hand,
can usually be avoided by taking trouble and by not always trusting
to physiological inference. Anybody can see double on purpose, by
focussing on a distant object and noticing a near one; but this will
not cause mistakes, since the man is aware of the subjective element in
his double vision. Similarly we are not deceived by after-images, and
only dogs are deceived by gramophones.

From what has been said in this chapter, it is clear that our knowledge
of the physical world, if it is to be made as reliable as possible,
must start from percepts, and must scrutinize the physiological
inferences by which percepts are accompanied. Physiological inference
is inference in the sense that it sometimes leads to error and physics
gives reason to expect that percepts will, in certain circumstances,
be more or less deceptive if taken as signs of something outside the
brain. It is these facts that give a subjective cast to the philosophy
of physics, at any rate in its beginnings. We cannot start cheerfully
with a world of matter in motion, as to which any two sane and sober
observers must agree. To some extent, each man dreams his own dream,
and the disentangling of the dream element in our percepts is no easy
matter. This is, indeed, the work that scientific physics undertakes to
do.




CHAPTER XIII

PHYSICAL AND PERCEPTUAL SPACE


Perhaps there is nothing so difficult for the imagination as to teach
it to feel about space as modern science compels us to think. This is
the task which must be attempted in the present chapter.

We said in Chapter XII that we know about what is happening in the
brain exactly what naive realism thinks it knows about what is
happening in the world. This remark may have seemed cryptic; it must
now be expanded and expounded.

The gist of the matter is that percepts, which we spoke about at the
end of last chapter, are in our heads; that percepts are what we can
know with most certainty; and that percepts contain what naive realism
thinks it knows about the world.

But when I say that my percepts are in my head, I am saying something
which is ambiguous until the different kinds of space have been
explained, for the statement is only true in connection with _physical_
space. There is also a space in our percepts, and of this space
the statement would not be true. When I say that there is space
in our percepts, I mean nothing at all difficult to understand. I
mean--to take the sense of sight, which is the most important in this
connection--that in what we see at one time there is up and down, right
and left, inside and outside. If we see, say, a circle on a blackboard,
all these relations exist within what we see. The circle has a top half
and a bottom half, a right-hand half and a left-hand half, an inside
and an outside. Those relations alone are enough to make up a space
of sorts. But the space of everyday life is filled out with what we
derive from touch and movement--how a thing feels when we touch it,
and what movements are necessary in order to grasp it. Other elements
also come into the genesis of the space in which everybody believes
who has not been troubled by philosophy; but it is unnecessary for
our purposes to go into this question any more deeply. The point that
concerns us is that a man’s percepts are private to himself: what I
see, no one else sees; what I hear, no one else hears; what I touch,
no one else touches; and so on. True, others hear and see something
very like what I hear and see, if they are suitably placed; but there
are always differences. Sounds are less loud at a distance; objects
change their visual appearance according to the laws of perspective.
Therefore it is impossible for two persons at the same time to have
exactly identical percepts. It follows that the space of percepts, like
the percepts, must be private; there are as many perceptual spaces as
there are percipients. My percept of a table is outside my percept of
my head, in my perceptual space; but it does not follow that it is
outside my head as a physical object in physical space. Physical space
is neutral and public: in this space, all my percepts are in my head,
even the most distant star _as I see it_. Physical and perceptual space
have relations, but they are not identical, and failure to grasp the
difference between them is a potent source of confusion.

To say that you see a star when you see the light that has come from it
is no more correct than to say that you see New Zealand when you see
a New Zealander in London. Your perception when (as we say) you see a
star is causally connected, in the first instance, with what happens
in the brain, the optic nerve, and the eye, then with a light-wave
which, according to physics, can be traced back to the star as its
source. Your sensations will be closely similar if the light comes from
a lamp at the top of a mast. The physical space in which you believe
the “real” star to be is an elaborate inference; what is given is the
private space in which the speck of light you see is situated. It is
still an open question whether the space of sight has depth, or is
merely a surface, as Berkeley contended. This does not matter for
our purposes. Even if we admit that sight alone shows a difference
between an object a few inches from the eyes and an object several feet
distant, yet you certainly cannot, by sight alone, see that a cloud
is less distant than a fixed star, though you may _infer_ that it is,
because it can hide the star. The world of astronomy, from the point of
view of sight, is a surface. If you were put in a dark room with little
holes cut in the ceiling in the pattern of the stars letting light come
through, there would be nothing in your immediate visual data to show
that you were not “seeing the stars”. This illustrates what I mean by
saying that what you see is _not_ “out there” in the sense of physics.

We learn in infancy that we can sometimes touch objects we see, and
sometimes not. When we cannot touch them at once, we can sometimes do
so by walking to them. That is to say, we learn to correlate sensations
of sight with sensations of touch, and sometimes with sensations of
movement followed by sensations of touch. In this way we locate our
sensations in a three-dimensional world. Those which involve sight
alone we think of as “external”, but there is no justification for this
view. What you see when you see a star is just as internal as what you
feel when you feel a headache. That is to say, it is internal from the
standpoint of _physical_ space. It is distant in your private space,
because it is not associated with sensations of touch, and cannot be
associated with them by means of any journey you can perform.

Your own body, as known to you through direct experience, is quite
different from your own body as considered in physics. You know more
about your own body than about any other through direct experience,
because your own body can give you a number of sensations that no other
body can, for instance all kinds of bodily pains. But you still know
it only through sensations; apart from inference, it _is_ a bundle of
sensations, and therefore quite different, _prima facie_, from what
physics calls a body.

Most of the things you see are outside what you see when (as one says)
you see your own body. That is to say: you see certain other patches of
colour, differently situated in visual space, and say you are seeing
things outside your body. But from the point of view of physics, all
that you see must count as inside your body; what goes on elsewhere
can only be inferred. Thus the whole space of your sensible world with
all its percepts counts as one tiny region from the point of view of
physics.

There is no direct spatial relation between what one person sees and
what another sees, because no two ever see exactly the same object.
Each person carries about a private space of his own, which can be
located in physical space by indirect methods, but which contains no
place in common with another person’s private space. This shows how
entirely physical space is a matter of inference and construction.

To make the matter definite, let us suppose that a physiologist is
observing a living brain--no longer an impossible supposition, as
it would have been formerly. It is natural to suppose that what the
physiologist sees is in the brain he is observing. But if we are
speaking of physical space, what the physiologist sees is in his
own brain. It is in no sense in the brain that he is observing,
though it is in the percept of that brain, which occupies part of
the physiologist’s perceptual space. Causal continuity makes the
matter perfectly evident: light-waves travel from the brain that is
being observed to the eye of the physiologist, at which they only
arrive after an interval of time, which is finite though short. The
physiologist sees what he is observing only after the light-waves have
reached his eye; therefore the event which constitutes his seeing comes
at the end of a series of events which travel from the observed brain
into the brain of the physiologist. We cannot, without a preposterous
kind of discontinuity, suppose that the physiologist’s percept,
which comes at the end of this series, is anywhere else but in the
physiologist’s head.

This question is very important, and must be understood if metaphysics
is ever to be got straight. The traditional dualism of mind and
matter, which I regard as mistaken, is intimately connected with
confusions on this point. So long as we adhere to the conventional
notions of mind and matter, we are condemned to a view of perception
which is miraculous. We suppose that a physical process starts from a
visible object, travels to the eye, there changes into another physical
process, causes yet another physical process in the optic nerve,
finally produces some effect in the brain, simultaneously with which
we see the object from which the process started, the seeing being
something “mental”, totally different in character from the physical
processes which precede and accompany it. This view is so queer
that metaphysicians have invented all sorts of theories designed to
substitute something less incredible. But nobody noticed an elementary
confusion.

To return to the physiologist observing another man’s brain: what the
physiologist sees is by no means identical with what happens in the
brain he is observing, but is a somewhat remote effect. From what he
sees, therefore, he cannot judge whether what is happening in the brain
he is observing is, or is not, the sort of event that he would call
“mental”. When he says that certain physical events in the brain are
accompanied by mental events, he is thinking of physical events as if
they were what he sees. He does not see a mental event in the brain he
is observing, and therefore supposes there is in that brain a physical
process which he can observe and a mental process which he cannot.
This is a complete mistake. In the strict sense, he cannot observe
anything in the other brain, but only the percepts which he himself has
when he is suitably related to that brain (eye to microscope, etc.).
We first identify physical processes with our percepts, and then,
since our percepts are not other people’s thoughts, we argue that the
physical processes in their brains are something quite different from
their thoughts. In fact, everything that we can directly observe of
the physical world happens inside our heads, and consists of “mental”
events in at least one sense of the word “mental”. It also consists
of events which form part of the physical world. The development of
this point of view will lead us to the conclusion that the distinction
between mind and matter is illusory. The stuff of the world may be
called physical or mental or both or neither, as we please; in fact,
the words serve no purpose. There is only one definition of the words
that is unobjectionable: “physical” is what is dealt with by physics,
and “mental” is what is dealt with by psychology. When, accordingly, I
speak of “physical” space, I mean the space that occurs in physics.

It is extraordinarily difficult to divest ourselves of the belief that
the physical world is the world we perceive by sight and touch; even
if, in our philosophic moments, we are aware that this is an error,
we nevertheless fall into it again as soon as we are off our guard.
The notion that what we see is “out there” in physical space is one
which cannot survive while we are grasping the difference between what
physics supposes to be really happening, and what our senses show us
as happening; but it is sure to return and plague us when we begin to
forget the argument. Only long reflection can make a radically new
point of view familiar and easy.

Our illustrations hitherto have been taken from the sense of sight;
let us now take one from the sense of touch. Suppose that, with your
eyes shut, you let your finger-tip press against a hard table. What
is really happening? The physicist says that your finger-tip and the
table consist, roughly speaking, of vast numbers of electrons and
protons; more correctly, each electron and proton is to be thought of
as a collection of processes of radiation, but we can ignore this for
our present purposes. Although you think you are touching the table,
no electron or proton in your finger ever really touches an electron
or proton in the table, because this would develop an infinite force.
When you press, repulsions are set up between parts of your finger and
parts of the table. If you try to press upon a liquid or a gas, there
is room in it for the parts that are repelled to get away. But if you
press a hard solid, the electrons and protons that try to get away,
because electrical forces from your finger repel them, are unable to
do so, because they are crowded close to others which elbow them back
to more or less their original position, like people in a dense crowd.
Therefore the more you press the more they repel your finger. The
repulsion consists of electrical forces, which set up in the nerves a
current whose nature is not very definitely known. This current runs
into the brain, and there has effects which, so far as the physiologist
is concerned, are almost wholly conjectural. But there is one effect
which is not conjectural, and that is the sensation of touch. This
effect, owing to physiological inference or perhaps to a reflex, is
associated by us with the finger-tip. But the sensation is the same
if, by artificial means, the parts of the nerve nearer the brain are
suitably stimulated--_e.g._ if your hand has been amputated and the
right nerves are skilfully manipulated. Thus our confidence that touch
affords evidence of the existence of bodies at the place which we think
is being touched is quite misplaced. As a rule we are right, but we can
be wrong; there is nothing of the nature of an infallible revelation
about the matter. And even in the most favorable case, the perception
of touch is something very different from the mad dance of electrons
and protons trying to jazz out of each other’s way, which is what
physics maintains is really taking place at your finger-tip. Or, at
least, it _seems_ very different. But as we shall see, the knowledge
we derive from physics is so abstract that we are not warranted
in saying that what goes on in the physical world is, or is not,
intrinsically very different from the events that we know through our
own experiences.




CHAPTER XIV

PERCEPTION AND PHYSICAL CAUSAL LAWS


In an earlier chapter we saw the inadequacy of the traditional notion
of cause, without adequately explaining the causal laws which are a
substitute in the practice of science. The time has now come when it
is possible to remedy this defect, and, in so doing, to fit perception
into its place in the chain of physical causation and recapitulate the
main points of previous arguments.

The old view was that an event A will always be followed by a certain
event B, and that the problem of discovering causal laws is the
problem, given an event B, of finding that event A which is its
invariable antecedent or _vice versa_. At an early stage of a science
this point of view is useful; it gives laws which are true usually,
though probably not always, and it affords the basis for more exact
laws. But it has no philosophical validity, and is superseded in
science as soon as we arrive at genuine laws. Genuine laws, in advanced
sciences, are practically always quantitative laws of _tendency_. I
will try to illustrate by taking the simplest possible case in physics.

Imagine a hydrogen atom, in which the electron is revolving not in
the minimum orbit, but in the next, which has four times the minimum
radius. So long as this state continues, the atom has no external
effects, apart from its infinitesimal gravitational action; we cannot,
therefore, obtain any evidence of its existence except when it changes
its state. In fact, our knowledge of atoms is like that which a ticket
collector has of the population of his town: he knows nothing of those
who stay quietly at home. Now at some moment, according to laws of
which we have only statistical knowledge, the electron in our atom
jumps to a smaller orbit, and the energy lost to the atom travels
outward in a light-wave. We know no causal law as to when the electron
will jump, though we know how far it will jump and exactly what will
happen in the neighbourhood when it does. At least, when I say we
know exactly what will happen, I ought to say that we know exactly
the mathematical laws of what will happen. A series of events, having
quantitative characteristics which obey certain equations, will travel
outward in all directions from the electron, and will proceed quite
regularly, like ripples on a pool, until other matter is encountered.
We have here one important and apparently fundamental kind of causal
law, the kind regulating the propagation of light _in vacuo_. This is
summed up in Maxwell’s equations, which enable us to calculate the
diffusion of an electro-magnetic disturbance starting from a source. So
long as two such disturbances do not meet, the matter is exceedingly
simple; but the equations also tell us what happens when they do
meet. We then have, as always in traditional physics, two separate
tendencies, which have a resultant compounded according to mathematical
laws, of which the parallelogram law is the oldest and simplest. That
is to say, each previous circumstance in the space-time neighbourhood
contributes a tendency, and the resulting event is obtained by
compounding these tendencies according to a mathematical law.

So far, we have been considering only electro-magnetic phenomena in
empty space. We have another set of facts about empty space, namely
those upon which gravitation depends. These have to do with the
structure of space-time, and show that this structure has singularities
in the regions where there is matter, which spread with diminishing
intensity as we get away from these regions. You may conceive the
structure of space-time on the analogy of a pond with a fountain
playing in it, so that wherever a spray falls from the fountain there
is a little hill of water which flattens quickly as you get away from
the spot where the spray falls. Here again the same sort of thing
applies: to infer the structure in a small region of space-time from
that in the neighbourhood, it will be necessary to superpose a number
of tendencies according to mathematical rules. Thus philosophically
this introduces no novelty.

But now consider what happens when the wave of light which started
from our hydrogen atom comes in contact with matter. Various things
may happen. The matter may absorb all or some of the energy of the
light-ray; this is the interesting case from our point of view. The
absorption may take the form of causing the electrons to move in larger
orbits, in which case, later, when they return to their previous
orbits, we get the phenomenon of fluorescence. Or the body may become
heated; or it may visibly move, like a radiometer. The effects upon
bodies depend upon the bodies as well as the light. Some of them can be
individually predicted, others can only be calculated in statistical
averages; this depends upon whether quantum considerations come in
or not. Where they do, we can enumerate possibilities, and state the
relative frequencies with which they will be realised, but we cannot
tell which will be realised in any given case.

So far, we have considered the radiation of energy from matter into
empty space, its propagation in empty space and its impact on matter
from empty space. We have not considered the history of a given piece
of matter, or the distinction between matter and empty space.

The essence of matter appears to be this: We can distinguish series of
events in space-time which have a certain kind of close resemblance
to each other, such that common sense regards them as manifestations
of one “thing”. But when we look closely at the question, it turns
out that what physics offers is something more abstract than this.
Take, _e. g._ the continued existence of a certain electron. This
means to say that events in a certain neighbourhood will be such as
can be calculated on the assumption that there is an electric charge
of a certain standard magnitude in the middle of that neighbourhood;
and that the neighbourhoods of which this is true form a tube in
space-time.

So long as we stick to the standpoint of pure physics there is a
certain air of taking in each other’s washing about the whole business.
Events in empty space are only known as regards their abstract
mathematical characteristics; matter is only an abstract mathematical
characteristic of events in empty space. This seems rather a cold
world. But as a matter of fact we know some things that are a little
more concrete. We know, _e.g._ what it feels like when we see things.
From the point of view of physics, when our light-wave starts out
through empty space, if it presently reaches our eye we know one link
in the causal chain, namely the visual sensation, otherwise than as a
term in an abstract mathematical formula. And it is this one term which
forms the basis for our belief in all the rest. Seeing is believing.

At this point I propose to make a brief digression on the subject of
our evidence for causal laws. The laws for which we first get evidence
are such as do not hold always, but only as a general rule. As a
rule, when you decide to move your arm, it moves: but sometimes it is
paralysed and remains motionless. As a rule, when you say how-do-you-do
to an old friend, he says the same to you; but he may have grown blind
and deaf since you last saw him, and not notice your words or gesture.
As a rule, if you put a match to gunpowder, it explodes; but it may
have got damp. It is such common but not invariable rules of sequence
that we notice first. But science is always seeking to replace them by
laws that may have no exceptions. We notice first that heavy bodies
fall, then that some bodies do not fall. Then we generalise both sets
of facts into the law of gravitation and the laws of resistance of the
air. These more general laws do not state that anything will actually
happen: they state a tendency, and lead to the conclusion that what
actually happens is the resultant of a number of tendencies. We cannot
know what the resultant will be unless we know a great deal about
the neighbourhood concerned. For example, I might, within the next
few seconds be hit on the head by a meteorite; to know whether this
is going to happen, I must know what matter is to be found in the
neighbourhood of the earth. This illustrates that actual predictions
based upon laws which are perfectly valid may always be falsified by
some unknown fact of what we may call geography. Moreover, we can
never be _sure_ that our scientific laws are quite right; of this the
Einsteinian modification of the law of gravitation has afforded a
notable instance.

Let us now return to the relation between perception and the causal
laws of physics.

Having realised the abstractness of what physics has to say, we no
longer have any difficulty in fitting the visual sensation into the
causal series. It used to be thought “mysterious” that purely physical
phenomena should end in something mental. That was because people
thought they knew a lot about physical phenomena, and were sure they
differed in quality from mental phenomena. We now realise that we know
nothing of the intrinsic quality of physical phenomena except when
they happen to be sensations, and that therefore there is no reason to
be surprised that some are sensations, or to suppose that the others
are totally unlike sensations. The gap between mind and matter has
been filled in, partly by new views of mind, but much more by the
realisation that physics tells us nothing as to the intrinsic character
of matter.

I conceive what happens when we see an object more or less on the
following lines. For the sake of simplicity, let us take a small
self-luminous object. In this object, a certain number of atoms are
losing energy and radiating it according to the quantum principle.
The resulting light-waves become superposed according to the usual
mathematical principles; each part of each light-wave consists of
events in a certain region of space-time. On coming in contact with the
human body, the energy in the light-wave takes new forms, but there
is still causal continuity. At last it reaches the brain, and there
one of its constituent events is what we call a visual sensation. This
visual sensation is popularly called seeing the object from which the
light-waves started--or from which they were reflected if the object
was not self-luminous.

Thus what is called a perception is only connected with its object
through the laws of physics. Its relation to the object is causal and
mathematical; we cannot say whether or not it resembles the object in
any intrinsic respect, except that both it and the object are brief
events in space-time.

I think we may lay down the following universal characteristics of
causal laws in an advanced science. Given any event, there are other
events at neighbouring places in space-time which will occur slightly
later if no other factors intervene; but in practice other factors
almost always do intervene, and, in that case, the event which actually
occurs at any point of space-time is a mathematical resultant of those
which would have followed the various neighbouring events if they had
been alone concerned. The equations of physics give the rules according
to which events are connected, but all are of the above sort.

Formerly it was thought that the equations of physics sufficed,
theoretically, to determine the course of affairs in the physical
world, given all the facts about some finite stretch of time, however
short. Now it appears that this is not the case, so far as the known
equations are concerned. The known equations suffice to determine what
happens in empty space, and statistical averages as to what happens to
matter; but they do not tell us when an individual atom will absorb or
radiate energy. Whether there are laws, other than those of statistics,
governing the behaviour of an individual atom in this respect, we do
not know.

It should be observed that there are causal laws of a different sort
from those of pure physics; such are the laws that light-waves “cause”
visual sensations and sound-waves “cause” auditory sensations. All the
empirical evidence for physics rests upon such laws, therefore nothing
in physics can have a higher degree of certainty than such laws have.
Let us stop a moment to ask what we mean by “cause” in this connection.

The connection of light-waves and visual sensations looks a little
different according as we start with physics or with psychology,
though, of course, ultimately the result must be the same. Let us
first start with physics. I say, then, that when a light-wave travels
outwards from a body there are successive events at successive places,
and that the corresponding event in a brain behind a normal eye is a
visual sensation. This is the only event in the whole series about
which I can say anything not purely abstract and mathematical.

Now let us start from the sensation. I say, then, that this sensation
is one of a vast series of connected events, travelling out from a
centre according to certain mathematical laws, in virtue of which the
sensation enables me to know a good deal about events elsewhere. That
is why the sensation is a source of physical knowledge.

It will be seen that, according to the view I have been advocating,
there is no difficulty about interaction between mind and body. A
sensation is merely one link in a chain of physical causation; when we
regard the sensation as the end of such a chain, we have what would
be regarded as an effect of matter on mind; when as the beginning,
an effect of mind on matter. But mind is merely a cross-section in a
stream of physical causation, and there is nothing odd about its being
both an effect and a cause in the physical world. Thus physical causal
laws are those that are fundamental.

There seems no reason to regard causation as _a priori_, though this
question is not simple. Given certain very general assumptions as to
the structure of space-time, there are bound to be what we have called
causal laws. These general assumptions must really replace causality
as our basic principles. But, general as they are, they cannot be
taken as _a priori_; they are the generalisation and abstract epitome
of the fact that there are causal laws, and this must remain merely
an empirical fact, which is rendered probable, though not certain, by
inductive arguments.




CHAPTER XV

THE NATURE OF OUR KNOWLEDGE OF PHYSICS


In this chapter, we shall seek an answer to two questions: First, _how_
do we know about the world dealt with in physics? Secondly, _what_ do
we know about it, assuming the truth of modern physics?

First: How do we know about the physical world? We have already seen
that this question cannot have a simple answer, since the basis of
inference is something that happens in our own heads, and our knowledge
of anything outside our own heads must be more or less precarious. For
the present, I shall take it for granted that we may accept testimony,
with due precautions. In other words, I shall assume that what we hear
when, as we believe, others are speaking to us, does in fact have
“meaning” to the speaker, and not only to us; with a corresponding
assumption as regards writing. This assumption will be examined at a
later stage. For the present, I will merely emphasise that it _is_ an
assumption, and that it may possibly be false, since people seem to
speak to us in dreams, and yet, on waking, we become persuaded that
we invented the dream. It is impossible to prove, by a demonstrative
argument, that we are not always dreaming; the best we can hope is a
proof that this is improbable. But for the present let us leave this
discussion on one side, and assume that the words we hear and read
“mean” what they would if we spoke or wrote them.

On this basis, we have reason to know that the worlds of different
people are alike in certain respects and different in certain others.
Take, for example, the audience at a theatre: they all, we say, hear
the same words and see the same gestures, which, moreover, are those
that the actors wish them to hear and see. But those who are near the
stage hear the words more loudly than those further off; they also
hear them somewhat earlier. And those who sit on the right do not see
quite what is seen by those who sit on the left or in the centre. These
differences are of two sorts: on the one hand, some people can see
something invisible to others; on the other hand, when two people, as
we say, see the “same” thing, they see it differently owing to effects
of perspective and of the way the light is reflected. All this is a
question of physics, not of psychology; for if we place a camera in an
empty seat in the theatre, the perspective in the resultant photograph
is intermediate between the perspectives that are seen by persons
sitting on either side; indeed the whole matter of perspective is
determined by quite simple geometrical laws. These laws show also what
is common to the shapes that two people see when they see the “same”
thing from different points of view: what is common is what is studied
by projective geometry, which is concerned with what is independent of
measurement in geometrical figures. All the differences in appearance
due to perspective have to be learned in learning to draw: for this
purpose, it is necessary to learn to see things as they really seem,
and not as they seem to seem.

But, it will be said, what can you mean by how things “really” seem
and how they “seem” to seem? We come here upon an important fact about
learning. When, in early infancy, we are learning to correlate sight
and touch, we acquire the habit of reacting to a visual stimulus in a
manner which is more “objective” than that in which a camera reacts.
When we see a coin not directly in front of us, we judge it to be
circular, although the camera would show it as oval, and a man would
have to make it oval in a picture of a scene which contained it. We
learn, therefore, to react to a visual shape in a manner corresponding
to how it would appear if it were in the centre of the field of vision,
provided we do not immediately focus upon it, which is what we
naturally do when anything visible interests us. As a matter of fact,
we are constantly looking in different directions, and, as a rule, only
noticing what, at the moment, is in the centre of our field of vision.
Thus our visual world consists rather of a synthesis of things viewed
directly in succession than of things seen simultaneously while the
centre of the field is kept fixed. This is one reason why the rules of
perspective have to be learned, although a picture which ignores them
makes an impression of being “wrong”.

Another reason for the objectivity of the impressions we derive from
sight is correlation with other senses, especially touch. Through
this correlation we soon get to “know” that a man twenty yards away
is “really” just as big as a man one yard away. When children are
learning to draw, they find it very difficult to make distant objects
sufficiently small, because they know they are not “really” small. We
soon learn to judge the distance of a visual object, and to react to
it according to the size that it would have if touched--or travelled
over--in the case of very large objects such as mountains. Our sense
of size is not derived from sight, but from such sources as touch and
locomotion; our metrical judgments, when the stimulus is only visual,
are a result of previous experience.

By the time a child can speak well, he has had a great deal of this
kind of experience. Consequently our verbal reactions contain a great
deal more objectivity than they would if they came at an earlier stage
of infancy. The result is that a number of people can view a scene
simultaneously, and use exactly the same words about it. The words
which we naturally use in describing what we see are those describing
features that will also be evident to others in our neighbourhood. We
say, “there is a man”, not, “there is a coloured shape whose visual
dimensions are such-and-such an angle vertically, and such another
horizontally”. The inference is a physiological inference, and only
subsequent reflection makes us aware that it has taken place. We
can, however, become aware of it through occasional mistakes; a dot
on the window-pane may be mistaken for a man in a distant field. In
this case, we can discover our error by opening the window, or by
moving the head. In general, however, physiological inferences of this
sort are correct, since they have resulted from correlations which
are very common, and are likely to be present on a given occasion.
Consequently our words tend to conceal what is private and peculiar in
our impressions, and to make us believe that different people live in a
common world to a greater extent than is in fact the case.

We have been using the word “objectivity” in the preceding pages,
and it is time to consider exactly what we mean by it. Suppose some
scene--say in a theatre--is simultaneously seen by a number of people
and photographed by a number of cameras. The impression made upon
a person or a camera is in some respects like that made upon other
persons and cameras, in other respects different. We shall call the
elements which are alike “objective” elements in the impression,
and those which are peculiar we shall call “subjective”. Thus those
features of shapes which are considered in projective geometry will
be objective, whereas those considered in metrical geometry (where
lengths and angles are measured) cannot be made objective through sight
alone, but demand the use of other senses. In the photographs, a man
on the stage will be longer if the camera is near the stage than if it
is far off, assuming all the cameras to be alike. But if four actors
are standing in a row in one photograph, they will be standing in a
row in another; this is an “objective” feature of the impression. And
the differences in the visual impressions of a number of spectators
with normal eyesight are exactly analogous to the differences in the
photographs; so also are the likenesses. Thus the “subjectivity” that
we are speaking about at present is something belonging to the physical
world, not to psychology. It marks the fact that the stimulus, whether
to an eye or to a camera, is not exactly the same wherever the eye or
the camera may be placed; there are features of the stimulus which are
constant (within limits), but there are others which are different from
any two different points of view.

The tendency of our perceptions is to emphasise increasingly the
objective elements in an impression, unless we have some special
reason, as artists have, for doing the opposite. This tendency begins
before speech, is much accentuated after speech has been acquired,
and is prolonged by scientific physics. The theory of relativity is
only the last term, so far, in the elimination of subjective elements
from impressions. But it must not be supposed that the subjective
elements are any less “real” than the objective elements; they are
only less important. They are less important because they do not point
to anything beyond themselves as the others do. We want our senses to
give us information, _i.e._ to tell us about something more than our
own momentary impression. We acquire information through our senses
if we attend to the objective elements in the impression and ignore
the others; but the subjective elements are just as truly part of the
actual impression. This is obvious as soon as we realise that the
camera is as subjective as we are.

Such considerations lead irresistibly to the scientific view that,
when an object can be seen or photographed from a number of points
of view, there is a connected set of events (light-waves) travelling
outward from a centre; that, moreover, there are some respects in
which all these events are alike, and others in which they differ one
from another. We must not think of a light-wave as a “thing”, but as a
connected group of rhythmical events. The mathematical characteristics
of such a group can be inferred by physics, within limits; but the
intrinsic character of the component events cannot be inferred. The
events constituting light-waves are only known through their effects
upon our eyes, optic nerves, and brains, and these effects are not
themselves light-waves, as is obvious from the fact that nerves and
brains are not transparent. Light in the physical world, therefore,
must consist of events which are in some way different from the events
which happen when we see; but we cannot say more than this as to the
intrinsic quality of these external events. Moreover, when a number of
people, as we say, “see the same thing”, what we have reason to believe
is that light-waves emanating from a certain region have reached the
eyes of all these people. As to what is in the region from which the
light-waves come, we cannot tell.

But--so the plain man is tempted to argue--we can tell quite well,
because we can touch objects that we see, and discover that there is
something hard and solid in the place from which the light-waves come.
Or, again, we may find that there is something there which, though not
solid, is very hot, and burns us when we try to touch it. We all feel
that touch gives more evidence of “reality” than sight; ghosts and
rainbows can be seen but not touched. One reason for this greater sense
of reality is that our spatial relation to an object when we touch it
with our finger-tips is given, and therefore an object does not give
such different impressions of touch to different people as it does of
sight. Another reason is that there are a number of objects that can be
seen but not touched--reflections, smoke, mist, etc.--and that these
objects are calculated to surprise the inexperienced. None of these
facts, however, justify the plain man in supposing that touch makes him
know real things as they are, though we are verbally forced to admit
that it brings him into “contact” with them.

We have seen on an earlier occasion how complex is the physical and
physiological process leading from the object to the brain when we
touch something; and we have seen that illusions of touch can be
produced artificially. What we experience when we have a sensation
of touch is, therefore, no more a revelation of the real nature of
the object touched than what we experience when we look at it. As a
matter of fact, if modern physics is to be believed, sight, prudently
employed, gives us a more delicate knowledge concerning objects
than touch can ever do. Touch, as compared with sight, is gross and
massive. We can photograph the path of an individual electron. We
perceive colours which indicate the changes happening in atoms. We can
see faint stars even though the energy of the light that reaches us
from them is inconceivably minute. Sight may deceive the unwary more
than touch, but for accurate scientific knowledge it is incomparably
superior to any of the other senses.

It is chiefly through ideas derived from sight that physicists have
been led to the modern conception of the atom as a centre from which
radiations travel. We do not know what happens in the centre. The idea
that there is a little hard lump there, which _is_ the electron or
proton, is an illegitimate intrusion of common-sense notions derived
from touch. For aught we know, the atom may consist entirely of the
radiations which come out of it. It is useless to argue that radiations
cannot come out of nothing. We know that they come, and they do not
become any more really intelligible by being supposed to come out of a
little lump.

Modern physics, therefore, reduces matter to a set of events which
proceed outward from a centre. If there is something further in the
centre itself, we cannot know about it, and it is irrelevant to
physics. The events that take the place of matter in the old sense are
inferred from their effect on eyes, photographic plates, and other
instruments. What we know about them is not their intrinsic character,
but their structure and their mathematical laws. Their structure is
inferred chiefly through the maxim “same cause, same effect”. It
follows from this maxim that if the effects are different, the causes
must be different; if, therefore, we see red and blue side by side,
we are justified in inferring that in the direction where we see
red something different is happening from what is happening in the
direction where we see blue. By extensions of this line of argument
we arrive at the mathematical laws of the physical world. Physics is
mathematical, not because we know so much about the physical world,
but because we know so little: it is only its mathematical properties
that we can discover. For the rest, our knowledge is negative. In
places where there are no eyes or ears or brains there are no colours
or sounds, but there are events having certain characteristics which
lead them to cause colours and sounds in places where there are eyes
and ears and brains. We cannot find out what the world looks like from
a place where there is nobody, because if we go to look there will be
somebody there; the attempt is as hopeless as trying to jump on one’s
own shadow.

Matter as it appears to common sense, and as it has until recently
appeared in physics, must be given up. The old idea of matter was
connected with the idea of “substance”, and this, in turn, with a view
of time that the theory of relativity shows to be untenable. The old
view was that there is one cosmic time, and that, given any two events
in any two parts of the universe, either they are simultaneous, or the
first is earlier than the second, or the second earlier than the first.
It was thought that the time-order of the two events must always be
objectively definite, although _we_ might be unable to determine it.
We now find that this is not the case. Events which can be regarded as
all in one place, or all parts of the history of one piece of matter,
still have a definite time-order. So do events in different places if a
person situated where the second takes place can see the first before
the second happens, or, more exactly, if light can travel from the
place of the one to the place of the other so as to reach the other
place before the second event. (Here we mean by a “place” the position
of a given piece of matter: however the matter may move relatively
to other matter, it is always in the same “place” from its own point
of view.) But if light travelling from the place of the one event to
the place of the other event arrives at the place of the other event
after the other event has taken place, and conversely, then there is
no definite objective time-order of the two events, and there is no
reason for regarding either as earlier than the other; nor yet for
regarding the two as simultaneous; ideally careful observers will judge
differently according to the way in which they are moving. Thus time
is not cosmic, but is to some extent individual and personal for each
piece of matter.

What do we mean by a “piece of matter” in this statement? We do not
mean something that preserves a simple identity throughout its history,
nor do we mean something hard and solid, nor even a hypothetical
thing-in-itself known only through its effects. We mean the “effects”
themselves, only that we no longer invoke an unknowable cause for
them. We find that energy in various forms spreads outwards from
various centres; we find also that such centres have a certain degree
of persistence, though this persistence is not absolute--the modern
physicist faces cheerfully the possibility that an electron and a
proton may mutually annihilate each other, and even suggests that this
may be the main source of the radiant energy of the stars, because
when it happens it makes an explosion. What is asserted may be put as
follows: When energy radiates from a centre, we can describe the laws
of its radiation conveniently by imagining something in the centre,
which we will call an electron or a proton according to circumstances,
and for certain purposes it is convenient to regard this centre as
persisting, _i.e._ as not a single point in space-time but a series
of such points, separated from each other by time-like intervals. All
this, however, is only a convenient way of describing what happens
elsewhere, namely the radiation of energy away from the centre. As to
what goes on in the centre itself, if anything, physics is silent.

What Dr. Whitehead calls the “pushiness” of matter disappears
altogether on this view. “Matter” is a convenient formula for
describing what happens where it isn’t. I am talking physics, not
metaphysics; when we come to metaphysics, we may be able, tentatively,
to add something to this statement, but science alone can hardly add
to it. Materialism as a philosophy becomes hardly tenable in view of
this evaporation of matter. But those who would formerly have been
materialists can still adopt a philosophy which comes to much the
same thing in many respects. They can say that the type of causation
dealt with in physics is fundamental, and that all events are subject
to physical laws. I do not wish, as yet, to consider how far such a
view should be adopted; I am only suggesting that it must replace
materialism as a view to be seriously examined.




PART III

MAN FROM WITHIN




CHAPTER XVI

SELF-OBSERVATION


It will be remembered that throughout Part I, we agreed to consider
only those facts about a man which can be discovered by external
observation, and we postponed the question whether this excluded any
genuine knowledge or not. The usual view is that we know many things
which could not be known without self-observation, but the behaviourist
holds that this view is mistaken. I might be inclined to agree wholly
with the behaviourist but for the considerations which were forced upon
us in Part II, when we were examining our knowledge of the physical
world. We were then led to the conclusion that, assuming physics to
be correct, the data for our knowledge of physics are infected with
subjectivity, and it is impossible for two men to observe the same
phenomenon except in a rough and approximate sense. This undermines the
supposed objectivity of the behaviourist method, at least in principle;
as a matter of degree, it may survive to some extent. Broadly speaking,
if physics is true and if we accept a behaviourist definition of
knowledge such as that of Chapter VIII, we ought, as a rule, to know
more about things that happen near the brain than about things that
happen far from it, and most of all about things that happen in the
brain. This _seemed_ untrue because people thought that what happens
in the brain is what the physiologist sees when he examines it; but
this, according to the theory of Chapter XII, happens in the brain of
the physiologist. Thus the _a priori_ objection to the view that we
know best what happens in our brains is removed, and we are led back
to self-observation as the most reliable way of obtaining knowledge.
This is the thesis which is to be expanded and sustained in the present
chapter.

As every one knows, the certainty of self-observation was the basis
of Descartes’ system, with which modern philosophy began. Descartes,
being anxious to build his metaphysic only upon what was absolutely
certain, set to work, as a preliminary, to doubt anything that he could
make himself doubt. He succeeded in doubting the whole external world,
since there might be a malicious demon who took pleasure in presenting
deceitful appearances to him. (For that matter, dreams would have
supplied a sufficient argument.) But he could not manage to doubt his
own existence. For, said he, I am really doubting; whatever else may be
doubtful, the fact that I doubt is indubitable. And I could not doubt
if I did not exist. He summed up the argument in his famous formula:
_I think, therefore I am_. And having arrived at this certainty, he
proceeded to build up the world again by successive inferences. Oddly
enough, it was very like the world in which he had believed before his
excursion into scepticism.

It is instructive to contrast this argument with Dr. Watson’s. Dr.
Watson, like Descartes, is sceptical of many things which others
accept without question; and, like Descartes, he believes that there
are some things so certain that they can be safely used as the basis
of a startling philosophy. But the things which Dr. Watson regards
as certain are just those which Descartes regarded as doubtful, and
the thing which Dr. Watson most vehemently rejects is just what
Descartes regarded as absolutely unquestionable. Dr. Watson maintains
that there is no such thing as thinking. No doubt he believes in
his own existence, but not because he thinks he can think. The
things that strike him as absolutely indubitable are rats in mazes,
time-measurements, physiological facts about glands and muscles, and so
on. What are we to think when two able men hold such opposite views?
The natural inference would be that _everything_ is doubtful. This may
be true, but there are degrees of doubtfulness, and we should like to
know which of these two philosophers, if either, is right as to the
region of minimum doubtfulness.

Let us begin by examining Descartes’ view. “I think, therefore I am” is
what he says, but this won’t do as it stands. What, from his own point
of view, he should profess to know is not “_I_ think”, but “there is
thinking”. He finds doubt going on, and says: There is doubt. Doubt
is a form of thought, therefore there is thought. To translate this
into “_I_ think” is to assume a great deal that a previous exercise
in scepticism ought to have taught Descartes to call in question. He
would say that thoughts imply a thinker. But why should they? Why
should not a thinker be simply a certain series of thoughts, connected
with each other by causal laws? Descartes believed in “substance”,
both in the mental and in the material world. He thought that there
could not be motion unless something moved, nor thinking unless some
one thought. No doubt most people would still hold this view; but in
fact it springs from a notion--usually unconscious--that the categories
of grammar are also the categories of reality. We have already seen
that “matter” is merely a name for certain strings of sets of events.
It follows that what we call motion of matter really means that the
centre of such a set of events at one time does not have the same
spatial relations to other events as the connected centre at another
time has to the connected other events. It does not mean that there is
a definite entity, a piece of matter, which is now in one place and
now in another. Similarly, when we say, “I think first this and then
that”, we ought not to mean that there is a single entity “I” which
“has” two successive thoughts. We ought to mean only that there are two
successive thoughts which have causal relations of the kind that makes
us call them parts of one biography, in the same sort of way in which
successive notes may be parts of one tune; and that these thoughts are
connected with the body which is speaking in the way (to be further
investigated) in which thoughts and bodies are connected. All this is
rather complicated, and cannot be admitted as part of any ultimate
certainty. What Descartes really felt sure about was a certain
occurrence, which he described in the words “I think”. But the words
were not quite an accurate representation of the occurrence; indeed,
words never can escape from certain grammatical and social requirements
which make them say at once more and less than we really mean. I think
we ought to admit that Descartes was justified in feeling sure that
there was a certain occurrence, concerning which doubt was impossible;
but he was not justified in bringing in the word “I” in describing this
occurrence, and it remains to be considered whether he was justified in
using the word “think”.

In using a general word such as “think”, we are obviously going beyond
the datum, from a logical point of view. We are subsuming a particular
occurrence under a heading, and the heading is derived from past
experience. Now all words are applicable to many occurrences; therefore
all words go beyond any possible datum. In this sense, it is impossible
ever to convey in words the particularity of a concrete experience; all
words are more or less abstract. Such, at least, is a plausible line
of argument, but I am by no means sure that it is valid. For example,
the sight of a particular dog may make the general word “dog” come
into your mind; you then know that it is a dog, but you may not notice
what sort of dog it is. In this sense, the knowledge with which we
start is abstract and general; that is to say, it consists of a learned
reaction to a stimulus of a certain sort. The reactions, at any rate
in so far as they are verbal, are more uniform than the stimuli. A
witness might be asked “Did you see a dog?” “Yes.” “What sort of dog?”
“Oh, just an ordinary dog; I don’t remember more about it.” That is to
say, the witness’s reaction consisted of the generalised word “dog”
and no more. One is almost reminded of quantum phenomena in the atom.
When light falls on a hydrogen atom, it may make the electron jump from
the first orbit to the second, or to the third, etc. Each of these
is a generalised reaction to a stimulus which has no corresponding
generality. So dogs and cats have each their individual peculiarities,
but the ordinary inobservant person responds with the generalised
reaction “dog” or “cat”, and the particularity of the stimulus leads to
no corresponding particularity in the knowledge-reaction.

To return to Descartes and his thinking: it is possible, according to
what we have just said, that Descartes knew he was thinking with more
certainty than he knew what he was thinking about. This possibility
requires that we should ask what he meant by “thinking”. And since, for
him, thinking was the primitive certainty, we must not introduce any
external stimulus, since he considered it possible to doubt whether
anything external existed.

Descartes used the word “thinking” somewhat more widely than we should
generally do nowadays. He included all perception, emotion, and
volition, not only what are called “intellectual” processes. We may
perhaps with advantage concentrate upon perception. Descartes would say
that, when he “sees the moon”, he is more certain of his visual percept
than he is of the outside object. As we have seen, this attitude is
rational from the standpoint of physics and physiology, because a given
occurrence in the brain is capable of having a variety of causes, and
where the cause is unusual common sense will be misled. It would be
theoretically possible to stimulate the optic nerve artificially in
just the way in which light coming from the moon stimulates it; in this
case, we should have the same experience as when we “see the moon”, but
should be deceived as to its external source. Descartes was influenced
by an argument of this sort, when he brought up the possibility of a
deceitful demon. Therefore what he felt certain about was not what
he had initially felt certain about, but what remained certain after
an argument as to the causes of perception. This brings us to a
distinction which is important, but difficult to apply; the distinction
between what we in fact do not doubt, and what we should not doubt if
we were completely rational. We do not in fact question the existence
of the sun and moon, though perhaps we might teach ourselves to do
so by a long course of Cartesian doubt. Even then, according to
Descartes, we could not doubt that we have the experiences which we
have hitherto called “seeing the sun” and “seeing the moon”, although
we shall need different words if we are to describe these experiences
correctly.

The question arises: Why should we not doubt everything? Why should we
remain convinced that we have these experiences? Might not a deceitful
demon perpetually supply us with false memories? When we say “a moment
ago I had the experience which I have hitherto called seeing the sun”,
perhaps we are deceived. In dreams we often remember things that never
happened. At best, therefore, we can be sure of our present momentary
experience, not of anything that happened even half a minute ago.
And before we can so fix our momentary experience as to make it the
basis of a philosophy, it will be past, and therefore uncertain. When
Descartes said “I think”, he may have had certainty; but by the time he
said “therefore I am”, he was relying upon memory, and may have been
deceived. This line of argument leads to complete scepticism about
everything. If we are to avoid such a result, we must have some new
principle.

In actual fact, we start by feeling certainty about all sorts of
things, and we surrender this feeling only where some definite argument
has convinced us that it is liable to lead to error. When we find any
class of primitive certainties which never leads to error, we retain
our convictions in regard to this class. That is to say, wherever we
feel initial certainty, we require an argument to make us doubt, not an
argument to make us believe. We may therefore take, as the basis of our
beliefs, any class of primitive certainties which cannot be shown to
lead us into error. This is really what Descartes does, although he is
not clear about it himself.

Moreover, when we have found an error in something of which we were
previously certain, we do not as a rule abandon entirely the belief
which misled us, but we seek, if we can, to modify it so that it
shall no longer be demonstrably false. This is what has happened
with perception. When we think we see an external object, we may be
deceived by a variety of causes. There may be a mirage or a reflection;
in this case, the source of the error is in the external world, and a
photographic plate would be equally deceived. There may be a stimulus
to the eye of the sort that makes us “see stars”, or we may see little
black dots owing to a disordered liver, in which case, the source of
the error is in the body but not in the brain. We may have dreams in
which we seem to see all sorts of things; in this case, the source
of the error is in the brain. Having gradually discovered these
possibilities of error, people have become somewhat wary as to the
objective significance of their perceptions; but they have remained
convinced that they really have the perceptions they thought they had,
although the common-sense interpretation of them is sometimes at fault.
Thus, while retaining the conviction that they are sure of something,
they have gradually changed their view as to what it is that they are
sure of. Nothing is known that tends to show error in the view that we
really have the percepts we think we have, so long as we are prudent
in interpreting them as signs of something external. That is the valid
basis for Descartes’ view that “thought” is more certain than external
objects. When “thought” is taken to mean the experiences which we
usually regard as percepts of objects, there are sound reasons for
accepting Descartes’ opinion to this extent.

Let us now take up Dr. Watson’s view. We shall find, if I am not
mistaken, that his position also is to a very large extent valid. That
being so, we shall seek to find an intermediate opinion, accepting what
seems valid and rejecting what seems doubtful in the contentions of
both protagonists.

Dr. Watson’s view as to what is most certain is one which is in entire
accordance with common sense. All psychological matters the plain man
regards as more or less open to question, but he has no doubts about
his office, his morning train, the tax-collector, the weather, and
the other blessings of this life. It may amuse him, in an idle hour,
to listen to some one playing with the idea that life is a dream, or
suggesting that the thoughts of the people in the train are more real
than the train. But unless he is a philosophical lecturer, he does not
countenance such notions in business hours. Who can imagine a clerk in
an office conceiving metaphysical doubts as to the existence of his
boss? Or would any railroad president regard with favour the theory
that his railroad is only an idea in the minds of the shareholders?
Such a view, he would say, though it is often sound as regards
gold-mines, is simply silly when it comes to a railroad: anybody can
see it, and can get himself run over if he wanders on the tracks under
the impression that they do not exist. Belief in the unreality of
matter is likely to lead to an untimely death, and that, perhaps, is
the reason why this belief is so rare, since those who entertained it
died out. We cannot dismiss the common-sense outlook as simply silly,
since it succeeds in daily life; if we are going to reject it in part,
we must be sure that we do so in favor of something equally tough as a
means of coping with practical problems.

Descartes says: I think, therefore I am. Watson says: There are rats in
mazes, therefore I don’t think. At least, a parodist might thus sum up
his philosophy. What Watson really says is more like this: (1) The most
certain facts are those which are public, and can be confirmed by the
testimony of a number of observers. Such facts form the basis of the
physical sciences: physics, chemistry, biology, anatomy, physiology,
to mention only those that are relevant to the matter in question. (2)
The physical sciences are capable of affording an explanation of all
the publicly observable facts about human behaviour. (3) There is no
reason to suppose that there are any facts about human beings that can
be known only in some other way. (4) In particular, “introspection”, as
a means of discovering by self-observation things that are in principle
undiscoverable by observation of others, is a pernicious superstition,
which must be swept away before any really sound knowledge of man
becomes possible. (5) And, as a corollary, there is no reason to
believe in the existence of “thought” as opposed to speech and other
bodily behaviour.

I have numbered the above propositions, as it is important to keep them
separate. On the whole, (1), (2), and (3) seem to me to be true, but
(4) and (5) seem to me to be false. Behaviourists, I think, incline to
the view that (4) and (5) follow from (1), (2), and (3); but this view
I attribute to what I should regard as errors concerning the basis of
physics. That is why it was necessary to discuss physics before coming
to a decision on this question of self-observation. But let us examine
each of the above propositions in turn.

(1) It is true that the facts upon which the physical sciences are
based are all of them public, in the sense that many men can observe
them. If a phenomenon is photographed, any number of people can inspect
the photograph. If a measurement is made, not only may several people
be present, but others can repeat the experiment. If the result does
not confirm the first observer, the supposed fact is rejected. The
publicity of physical facts is always regarded as one of the greatest
assets of physics. On a common-sense basis, therefore, the first of the
propositions in which we have summed up the behaviourist philosophy
must be admitted.

There are, however, some very important provisos which must be
mentioned. In the first place, a scientific observer is not expected
to note his integral reaction to a situation, but only that part of it
which experience leads him to regard as “objective”, _i.e._ the same as
the reaction of any other competent observer. This process of learning
to note only “objective” features in our reaction is, as we have seen,
begun in infancy; training in science only carries it further. A “good”
observer does not mention what is peculiar to himself in his reaction.
He does not say: “A boring speck of light danced about, causing me
eye-fatigue and irritation; finally it settled at such-and-such a
point.” He says simply: “The reading was such-and-such”. All this
objectivity is a result of training and experience. One may say, in
fact, that very few men have the “right” reaction to a scientific
situation. Therefore an immense amount of theory is mixed up with what
passes in science as pure observation. The nature and justification of
this theory is a matter requiring investigation.

In the second place, we must not misinterpret the nature of the
publicity in the case of physical phenomena. The publicity consists in
the fact that a number of people make closely similar reactions at a
given moment. Suppose, for example, that twelve men are told to watch a
screen for the appearance of a bright light, and to say “now” when it
appears. Suppose the experimenter hears them all just when he himself
sees the light; then he has good reason to believe that they have each
had a stimulus similar to his. But physics compels us to hold that they
have had twelve separate stimuli, so that when we say they have all
seen the same light we can only legitimately mean that their twelve
stimuli had a common causal origin. In attributing our perceptions to a
normal causal origin outside ourselves, we run a certain risk of error,
since the origin may be unusual: there may be reflection or refraction
on the way to the eye, there may be an unusual condition of the eye
or optic nerve or brain. All these considerations give a certain very
small probability that, on a given occasion, there is not such an
outside cause as we suppose. If, however, a number of people concur
with us, _i.e._ simultaneously have reactions which they attribute to
an outside cause that can be identified with the one we had inferred,
then the probability of error is enormously diminished. This is exactly
the usual case of concurrent testimony. If twelve men, each of whom
lies every other time that he speaks, independently testify that some
event has occurred, the odds in favour of their all speaking the truth
are 4095 to 1. The same sort of argument shows that our public senses,
when confirmed by others, are probably speaking the truth, except where
there are sources of collective illusion such as mirage or suggestion.

In this respect, however, there is no _essential_ difference between
matters of external observation and matters of self-observation.
Suppose, for example, that, for the first time in your life, you smell
assafœtida. You say to yourself “that is a most unpleasant smell”. Now
unpleasantness is a matter of self-observation. It may be _correlated_
with physiological conditions which can be observed in others, but it
is certainly not identical with these, since people knew that things
were pleasant and unpleasant before they knew about the physiological
conditions accompanying pleasure and its opposite. Therefore when
you say “that smell is unpleasant” you are noticing something that
does not come into the world of physics as ordinarily understood. You
are, however, a reader of psycho-analysis, and you have learned that
sometimes hate is concealed love and love is concealed hate. You say to
yourself, therefore: “Perhaps I really like the smell of assafœtida,
but am ashamed of liking it”. You therefore make your friends smell it,
with the result that you soon have no friends. You then try children,
and finally chimpanzees. Friends and children give verbal expression
to their disgust: chimpanzees are expressive, though not verbal. All
these facts lead you to state: “The smell of assafœtida is unpleasant”.
Although self-observation is involved, the result has the same kind of
certainty, and the same kind of objective verification, as if it were
one of the facts that form the empirical basis of physics.

(2) The second proposition, to the effect that the physical sciences
are capable of affording an explanation of all the publicly observable
facts about human behaviour, is one as to which it is possible to argue
endlessly. The plain fact is that we do not yet know whether it is true
or false. There is much to be said in its favour on general scientific
grounds, particularly if it is put forward, not as a dogma, but as a
methodological precept, a recommendation to scientific investigators
as to the direction in which they are to seek for solution of their
problems. But so long as much of human behaviour remains unexplained
in terms of physical laws, we cannot assert dogmatically that there is
no residue which is theoretically inexplicable by this method. We may
say that the trend of science, so far, seems to render such a view
improbable, but to say even so much is perhaps rash, though, for my
part, I should regard it as still more rash to say that there certainly
is such a residue. I propose, therefore, as a matter of argument, to
admit the behaviourist position on this point, since my objections to
behaviourism as an ultimate philosophy come from quite a different kind
of considerations.

(3) The proposition we are now to examine may be stated as follows:
“All facts that can be known about human beings are known by the
same method by which the facts of physics are known.” This I hold to
be true, but for a reason exactly opposite to that which influences
the behaviourist. I hold that the facts of physics, like those of
psychology, are obtained by what is really self-observation, although
common sense mistakenly supposes that it is observation of external
objects. As we saw in Chapter XIII, your visual, auditory, and other
percepts are all in your head, from the standpoint of physics.
Therefore, when you “see the sun”, it is, strictly speaking, an event
in yourself that you are knowing: the inference to an external cause
is more or less precarious, and is on occasion mistaken. To revert to
the assafœtida: it is by a number of self-observations that you know
that the smell of assafœtida is unpleasant, and it is by a number of
self-observations that you know that the sun is bright and warm. There
is no essential difference between the two cases. One may say that the
data of psychology are those private facts which are not very directly
linked with facts outside the body, while the data of physics are those
private facts which have a very direct causal connection with facts
outside the body. Thus physics and psychology have the same method;
but this is rather what is commonly taken to be the special method of
psychology than what is regarded as the method of physics. We differ
from the behaviourist in assimilating physical to psychological method,
rather than the opposite.

(4) Is there a source of knowledge such as is believed in by those
who appeal to “introspection”? According to what we have just been
saying, all knowledge rests upon something which might, in a sense, be
called “introspection”. Nevertheless, there may be some distinction to
be discovered. I think myself that the only distinction of importance
is in the degree of correlation with events outside the body of the
observer. Suppose, for example, that a behaviourist is watching a rat
in a maze, and that a friend is standing by. He says to the friend
“Do you see that rat?” If the friend says yes, the behaviourist is
engaged in his normal occupation of observing physical occurrences.
But if the friend says no, the behaviourist exclaims, “I must give up
this boot-legged whiskey”. In that case, if his horror still permits
him to think clearly, he will be obliged to say that in watching the
imaginary rat he was engaged in introspection. There was certainly
something happening, and he could still obtain knowledge by observing
what was happening, provided he abstained from supposing that it had
a cause outside his body. But he cannot, without outside testimony
or some other extraneous information, distinguish between the “real”
rat and the “imaginary” one. Thus in the case of the “real” rat also,
his primary datum ought to be considered introspective, in spite of
the fact that it does not seem so; for the datum in the case of the
“imaginary” rat also does not _seem_ to be merely introspective.

The real point seems to be this: some events have effects which radiate
all round them, and can therefore produce reactions in a number of
observers; of these, ordinary speech is an illustration. But other
events produce effects which travel linearly, not spherically; of
these, speech into a telephone from a sound-proof telephone box may
serve as an illustration. This can be heard by only one person beside
the speaker; if instead of a speaker we had an instrument at the
mouthpiece, only one person could hear the sound, namely the person
at the other end of the telephone. Events which happen inside a human
body are like the noise in the telephone: they have effects, in the
main, which travel along nerves to the brain, instead of spreading
out in all directions equally. Consequently, a man can know a great
deal about his own body which another man can only know indirectly.
Another man can see the hole in my tooth, but he cannot feel my
toothache. If he infers that I feel toothache, he still does not have
the very same knowledge that I have; he may use the same words, but
the stimulus to his use of them is different from the stimulus to
mine, and I can be acutely aware of the pain which is the stimulus to
my words. In all these ways a man has knowledge concerning his own
body which is obtained differently from the way in which he obtains
knowledge of other bodies. This peculiar knowledge is, in one sense,
“introspective”, though not quite in the sense that Dr. Watson denies.

(5) We come now to the real crux of the whole matter, namely to the
question: Do we think? This question is very ambiguous, so long as
“thinking” has not been clearly defined. Perhaps we may state the
matter thus: Do we know events in us which would not be included in
an absolutely complete knowledge of physics? I mean by a complete
knowledge of physics a knowledge not only of physical laws, but also
of what we may call geography, _i.e._ the distribution of energy
throughout space-time. If the question is put in this way, I think it
is quite clear that we do know things not included in physics. A blind
man could know the whole of physics, but he could not know what things
look like to people who can see, nor what is the difference between
red and blue as seen. He could know all about wave-lengths, but people
knew the difference between red and blue as seen before they knew
anything about wave-lengths. The person who knows physics and can see
knows that a certain wave-length will give him a sensation of red, but
this knowledge is not part of physics. Again, we know what we mean by
“pleasant” and “unpleasant”, and we do not know this any better when
we have discovered that pleasant things have one kind of physiological
effect and unpleasant things have another. If we did not already know
what things are pleasant and what unpleasant, we could never have
discovered this correlation. But the knowledge that certain things are
pleasant and certain others unpleasant is no part of physics.

Finally, we come to imaginations, hallucinations, and dreams. In all
these cases, we may suppose that there is an external stimulus, but
the cerebral part of the causal chain is unusual, so that there is not
in the outside world something connected with what we are imagining
in the same way as in normal perception. Yet in such cases we can
quite clearly know what is happening to us; we can, for example,
often remember our dreams. I think dreams must count as “thought”, in
the sense that they lie outside physics. They may be accompanied by
movements, but knowledge of them is not knowledge of these movements.
Indeed all knowledge as to movements of matter is inferential, and
the knowledge which a scientific man should take as constituting
his primary data is more like our knowledge of dreams than like our
knowledge of the movements of rats or heavenly bodies. To this extent,
I should say, Descartes is in the right as against Watson. Watson’s
position seems to rest upon naive realism as regards the physical
world, but naive realism is destroyed by what physics itself has to say
concerning physical causation and the antecedents of our perceptions.
On these grounds, I hold that self-observation can and does give us
knowledge which is not part of physics, and that there is no reason to
deny the reality of “thought”.




CHAPTER XVII

IMAGES


In this chapter we shall consider the question of images. As the reader
doubtless knows, one of the battle-cries of behaviourism is “death
to images”. We cannot discuss this question without a good deal of
previous clearing of the ground.

What are “images” as conceived by their supporters? Let us take this
question first in the sense of trying to know some of the phenomena
intended, and only afterwards in the sense of seeking a formal
definition.

In the ordinary sense, we have visual images if we shut our eyes and
call up pictures of scenery or faces we have known; we have auditory
images when we recall a tune without actually humming it; we have
tactual images when we look at a nice piece of fur and think how
pleasant it would be to stroke it. We may ignore other kinds of images,
and concentrate upon these, visual, auditory, and tactual. There is no
doubt that we have such experiences as I have suggested by the above
words; the only question is as to how these experiences ought to be
described. Then we have another set of experiences, namely dreams,
which feel like sensations at the moment, but do not have the same kind
of relation to the external world as sensations have. Dreams, also,
indubitably occur, and again it is a question of analysis whether we
are to say that they contain “images” or not.

The behaviourist does not admit images, but he equally does not
admit sensations and perceptions. Although he does not say so quite
definitely, he may be taken to maintain that there is nothing but
matter in motion. We cannot, therefore, tackle the question of images
by contrasting them with sensations or perceptions, unless we have
first clearly proved the existence of these latter and defined their
characteristics. Now it will be remembered that in Chapter V we
attempted a behaviourist definition of perception, and decided that its
most essential feature was “sensitivity”. That is to say, if a person
always has a reaction of a certain kind B when he has a certain spatial
relation to an object of a certain kind A, but not otherwise, then we
say that the person is “sensitive” to A. In order to obtain from this a
definition of “perception”, it is necessary to take account of the law
of association; but for the moment we will ignore this complication,
and say that a person “perceives” any feature of his environment, or
of his own body, to which he is sensitive. Now, however, as a result
of the discussion in Chapter XVI, we can include in his reaction, not
only what others can observe, but also what he alone can observe.
This enlarges the known sphere of perception, practically if not
theoretically. But it leaves unchanged the fact that the essence
of perception is a causal relation to a feature of the environment
which, except in astronomy, is approximately contemporaneous with the
perception, though always at least slightly earlier, owing to the
time taken by light and sound to travel and the interval occupied in
transmitting a current along the nerves.

Let us now contrast with this what happens when you sit still with
your eyes shut, calling up pictures of places you have seen abroad,
and perhaps ultimately falling asleep. Dr. Watson, if I understand
him aright, maintains that either there is actual stimulation of the
retina, or your pictures are mere word-pictures, the words being
represented by small actual movements such as would, if magnified and
prolonged, lead to actual pronunciation of the words. Now if you are
in the dark with your eyes shut, there is no stimulation of the retina
from without. It may be that, by association, the eye can be affected
through stimuli to other senses; we have already had an example in the
fact that the pupil can be taught to contract at a loud noise if this
had been frequently experienced along with a bright light. We cannot,
therefore, dismiss the idea that a stimulus to one sense may, as a
result of past events, have an effect upon the organs of another sense.
“Images” might be definable as effects produced in this way. It may be
that, when you see a picture of Napoleon, there is an effect upon your
aural nerves analogous to that of having the word “Napoleon” pronounced
in your presence, and that that is why, when you see the picture, the
word “Napoleon” comes into your head. And similarly, when you shut
your eyes and call up pictures of foreign scenes, you may actually
pronounce, completely or incipiently, the word “Italy”, and this may,
through association, stimulate the optic nerve in a way more or less
similar to that in which some actual place in Italy stimulated it on
some former occasion. Thence association alone may carry you along
through a series of journeys, until at last, when you fall asleep, you
think you are actually making them at the moment. All this is quite
possible, but so far as I know there is no reason to hold that it is
more than possible, apart from an _a priori_ theory excluding every
other explanation.

What I think is clearly untenable is the view, sometimes urged by Dr.
Watson, that when we are, as we think, seeing imaginary pictures with
the eyes shut, we are really only using such words as would describe
them. It seems to me as certain as anything can be that, when I
visualise, something is happening which is connected with the sense of
sight. For example, I can call up quite clear mental pictures of the
house in which I lived as a child; if I am asked a question as to the
furniture of any of the rooms in that house, I can answer it by first
calling up an image and then looking to see what the answer is, just
as I should look to see in an actual room. It is quite clear to me
that the picture comes first and that words after; moreover, the words
need not come at all. I cannot tell what is happening in my retina or
optic nerve at these moments of visualisation, but I am quite sure
that something is happening which has a connection with the sense of
sight that it does not have with other senses. And I can say the same
of aural and tactual images. If this belief were inconsistent with
anything else that seems to me equally certain, I might be induced to
abandon it. But so far as I can see, there is no such inconsistency.

It will be remembered that we decided in favour of perceptions as
events distinct from those which they perceive, and only causally
connected with them. There is, therefore, no reason why association
should not work in this region as well as in the region of muscles
and glands; in other words, there is no reason to deny what used to
be called “association of ideas”, in spite of the fact that bodily
changes can also be associated. If a physical basis is wanted, it can
be assumed to exist in the brain. The state of the brain which causes
us to hear the word “Napoleon” may become associated with the state of
brain which causes us to see a picture of Napoleon, and thus the word
and the picture will call each other up. The association _may_ be in
the sense-organs or nerves, but may equally well be in the brain. So
far as I know, there is no conclusive evidence either way, nor even
that the association is not purely “mental.”

When we try to find a definition of the difference between a sensation
and an image, it is natural to look first for intrinsic differences.
But intrinsic differences between ordinary sensations and ordinary
images, for example as to “liveliness”, are found to be subject to
exceptions, and therefore unsuitable for purposes of definition. Thus
we are brought to differences as to causes and effects.

It is obvious that, in an ordinary case, you perceive a table because
(in some sense) the table is there. That is to say, there is a causal
chain leading backwards from your perception to something outside your
body. This alone, however, is hardly sufficient as a criterion. Suppose
you smell peat smoke and think of Ireland, your thought can equally be
traced to a cause outside your body. The only real difference is that
the outside cause (peat smoke) would not have had the effect (images
of Ireland) upon every normal person, but only upon such as had smelt
peat smoke in Ireland, and not all of them. That is to say, the normal
cerebral apparatus does not cause the given stimulus to produce the
given effect except where certain previous experiences have occurred.
This is a very vital distinction. Part of what occurs in us under the
influence of a stimulus from without depends upon past experience; part
does not. The former part includes images, the latter consists of pure
sensations. This, however, as we shall see later, is inadequate as a
definition.

Mental occurrences which depend upon past experience are called
“mnemic” occurrences, following Semon. Images are thus to be included
among mnemic occurrences, at least so far as human experience goes.
This, however, does not suffice to define them, since there are others,
_e.g._ recollections. What further defines them is their similarity
to sensations. This only applies strictly to simple images; complex
ones may occur without a prototype, though all their parts will have
prototypes among sensations. Such, at least, is Hume’s principle, and
on the whole it seems to be true. It must not, however, be pressed
beyond a point. As a rule, an image is more or less vague, and has a
number of similar sensations as its prototypes. This does not prevent
the connection with sensation in general, but makes it a connection
with a number of sensations, not with one only.

It happens that, when a complex of sensations has occurred at some
time in a person’s experience, the recurrence of part of the whole
tends to produce images of the remaining parts or some of them. This is
association, and has much to do with memory.

It is common to speak of images as “centrally excited”, as opposed to
sensations, which are excited by a stimulus to some sense organ. In
essence this is quite correct, but there is need of some caution in
interpreting the phrase. Sensations also have _proximate_ causes in
the brain; images also may be due to some excitement of a sense-organ,
when they are roused by a sensation through association. But in such
cases there is nothing to explain their occurrence except the past
experience and its effect on the brain. They will not be aroused by
the same stimulus in a person with similar sense-organs but different
past experience. The connection with past experience is clearly known;
it is, however, an explanatory hypothesis, not directly verifiable in
the present state of knowledge, to suppose that this connection works
through an effect of the past experience on the brain. This hypothesis
must be regarded as doubtful, but it will save circumlocution to adopt
it. I shall therefore not repeat, on each occasion, that we cannot feel
sure it is true. In general, where the causal connection with past
experience is obvious, we call an occurrence “mnemic”, without implying
this or that hypothesis as to the explanation of mnemic phenomena.

It is perhaps worth while to ask how we know that images are like the
sensations which are their prototypes. The difficulty of this question
arises as follows. Suppose you call up an image of the Brooklyn
Bridge, and you are convinced that it is like what you see when you
look at Brooklyn Bridge. It would seem natural to say that you know
the likeness because you remember Brooklyn Bridge. But remembering is
often held to involve, as an essential element, the occurrence of an
image which is regarded as referring to a prototype. Unless you can
remember without images, it is difficult to see how you can be sure
that images resemble prototypes. I think that in fact you cannot be
sure, unless you can find some indirect means of comparison. You might,
for example, have photographs of Brooklyn Bridge taken from a given
place on two different days, and find them indistinguishable, showing
that Brooklyn Bridge has not changed in the interval. You might see
Brooklyn Bridge on the first of these days, remember it on the second,
and immediately afterwards look at it. In looking at it, you might find
every detail coming to you with a feeling of expectedness, or you might
find some details coming with a feeling of surprise. In this case you
would say that your image had been wrong as regards the details which
were surprising. Or, again, you might make a picture of Brooklyn Bridge
on paper, from memory, and then compare it with the original or a
photograph. Or you might content yourself by writing down a description
of it in words, and verifying its accuracy by direct observation.
Innumerable methods of this kind can be devised by which you can test
the likeness of an image to its prototype. The result is that there is
often a great likeness, though seldom complete accuracy. The belief in
the likeness of an image to its prototype is, of course, not generated
in this way, but only tested. The belief exists prior to evidence as to
its correctness, like most of our beliefs. I shall have more to say on
this subject in the next chapter, which will be concerned with memory.
But I think enough has been said to show that it is not unreasonable
to regard images as having a greater or less degree of resemblance to
their prototypes. To claim more is hardly justifiable.

We can now reach a definite conclusion about perception, sensation, and
images. Let us imagine a number of people placed, as far as possible,
in the same environment; we will suppose that they sit successively in
a certain chair in a dark room, in full view of illuminated pictures
of two eminent politicians of opposite parties whose names are written
underneath them. We will suppose that all of them have normal eyesight.
Their reactions will be partly similar, partly different. If any of
these observers are babies too young to have learnt to focus, they will
not see sharp outlines, but a mere blurr, not from an optical defect,
but from a lack of cerebral control over muscles. In this respect,
experience has an effect even upon what must count as pure sensation.
But this difference is really analogous to the difference between
having one’s eyes open and having them shut; the difference is in the
sense-organ, although it may be due to a difference in the brain. We
will therefore assume that all the spectators know how to adjust the
eyes so as to see as well as possible, and all try to see. We shall
then say that, if the spectators differ as widely as is possible for
normal human beings, what is common to the reactions of all of them
is sensation, provided it is connected with the sense of sight, or,
more correctly, provided it has that quality which we observe to be
common and peculiar to visual objects. But probably all of them, if
they are over three months old, will have tactile images while they
see the pictures. And if they are more than about a year old, they
will interpret them as pictures, which represent three-dimensional
objects; before that age, they may see them as coloured patterns,
not as representations of faces. Most animals, though not all, are
incapable of interpreting pictures as representations. But in an adult
human being this interpretation is not deliberate; it has become
automatic. It is, I think, mainly a question of tactile images: the
images you have in looking at a picture are not those appropriate to a
smooth flat surface, but those appropriate to the object represented.
If the object represented is a large one, there will also be images of
movement--walking round the object, or climbing up it, or what not.
All these are obviously a product of experience, and therefore do not
count as part of the sensation. This influence of experience is still
more obvious when it comes to reading the names of the politicians,
considering whether they are good likenesses, and feeling what a fine
fellow one of them looks and what unmitigated villainy is stamped upon
the features of the other. None of this counts as sensation, yet it is
part of a man’s spontaneous reaction to an outside stimulus.

It is evidently difficult to avoid a certain artificiality in
distinguishing between the effects of experience and the rest in a
man’s reaction to a stimulus. Perhaps we could tackle the matter in a
slightly different way. We can distinguish stimuli of different sorts:
to the eye, the ear, the nose, the palate, etc. We can also distinguish
elements of different sorts in the reaction: visual elements, auditory
elements, etc. The latter are defined, not by the stimulus, but by
their intrinsic quality. A visual sensation and a visual image have
a common quality which neither shares with an auditory sensation or
an auditory image. We may then say: a visual image is an occurrence
having the visual quality but not due to a stimulus to the eye, _i.e._
not having as a direct causal antecedent the incidence of light-waves
upon the retina. Similarly an auditory image will be an occurrence
having the auditory quality but not due to sound-waves reaching the
ear, and so on for the other senses. This means a complete abandonment
of the attempt to distinguish psychologically between sensations and
images; the distinction becomes solely one as to physical antecedents.
It is true that we can and do arrive at the distinction without
scientific physics, because we find that certain elements in our
integral reactions have the correlations that make us regard them as
corresponding to something external while others do not--correlations
both with the experience of others and with our own past and future
experiences. But when we refine upon this common-sense distinction and
try to make it precise, it becomes the distinction in terms of physics
as stated just now.

We might therefore conclude that an image is an occurrence having the
quality associated with stimulation by some sense-organ, but not due
to such stimulation. In human beings, images seem to depend upon past
experience, but perhaps in more instinctive animals they are partly due
to innate cerebral mechanisms. In any case dependence upon experience
is not the mark by which they are to be defined. This shows how
intimate is the dependence of traditional psychology upon physics, and
how difficult it is to make psychology into an autonomous science.

There is, however, still a further refinement necessary. Whatever is
included under our present definition is an image, but some things
not included are also images. The sight of an object may bring with
it a visual image of some other object frequently associated with it.
This latter is called an image, not a sensation, because, though also
visual, it is not appropriate to the stimulus in a certain sense: it
would not appear in a photograph of the scene, or in a photograph
of the retina. Thus we are forced to say: the sensation element in
the reaction to a stimulus is that part which enables you to draw
inferences as to the nature of the extra-cerebral event (if any)
which was the stimulus;[9] the rest is images. Fortunately, images
and sensations _usually_ differ in intrinsic quality; this makes it
possible to get an approximate idea of the external world by using the
usual intrinsic differences, and to correct it afterwards by means of
the strict causal definition. But evidently the matter is difficult
and complicated, depending upon physics and physiology, not upon pure
psychology. This is the main thing to be realised about images.

      [9] _I.e._ the immediate stimulus, not the “physical object”.

The above discussion has suggested a definition of the word “image”.
We might have called an event an “image” when it is recognisably of
the same kind as a “percept”, but does not have the stimulus which it
would have if it were a percept. But if this definition is to be made
satisfactory, it will be necessary to substitute a different word in
place of “percept”. For example, in the percept of a visible object
it would be usual to include certain associated tactual elements, but
these must, from our point of view, count as images. It will be better
to say, therefore, that an “image” is an occurrence recognisably visual
(or auditory, etc., as the case may be), but not caused by a stimulus
which is of the nature of light (or sound etc., as the case may be), or
at any rate only indirectly so caused as a result of association. With
this definition, I do not myself feel any doubt as to the existence of
images. It is clear that they constitute most of the material of dreams
and day-dreams, that they are utilised by composers in making music,
that we employ them when we get out of a familiar room in the dark
(though here the rats in mazes make a different explanation possible),
and that they account for the shock of surprise we have when we take
salt thinking it is sugar or (as happened to me recently) vinegar
thinking it is coffee. The question of the causation of images--_i.e._
whether it is in the brain or in other parts of the body--is not one
which it is necessary to our purposes to decide, which is fortunate,
since, so far as I know, there is not at present any adequate evidence
on the point. But the existence of images and their resemblance to
perception is important, as we shall see in the next chapter.

Images come in various ways, and play various parts. There are
those that come as accretions to a case of sensation, which are not
recognised as images except by the psychologist; these form, for
example, the tactual quality of things we only see, and the visual
quality of things we only touch. I think dreams belong, in part, to
this class of images: some dreams result from misinterpreting some
ordinary stimulus, and in these cases the images are those suggested
by a sensation, but suggested more uncritically than if we were awake.
Then there are images which are not attached to a present reality, but
to one which we locate in the past; these are present in memory, not
necessarily always, but sometimes. Then there are images not attached
to reality at all so far as our feeling about them goes: images which
merely float into our heads in reverie or in passionate desire.
And finally there are images which are called up voluntarily, for
example, in considering how to decorate a room. This last kind has its
importance, but I shall say nothing more about it at present, since we
cannot profitably discuss it until we have decided what we are to mean
by the word “voluntary”. The first kind, which comes as an accretion
to sensation, and gives to our feeling of objects a certain rotundity
and full-bloodedness which the stimulus alone would hardly warrant, has
been considered already. Therefore what remains for the present is the
use of images in memory and imagination; and of these two I shall begin
with memory.




CHAPTER XVIII

IMAGINATION AND MEMORY


In this chapter we have to consider the two topics of imagination and
memory. The latter has already been considered in Chapter VI, but there
we viewed it from outside. We want now to ask ourselves whether there
is anything further to be known about it by taking account of what is
only perceptible to the person remembering.

As regards the part played by images, I do not think this is essential.
Sometimes there are memory-images, sometimes not; sometimes when images
come in connection with memory, we may nevertheless know that the
images are incorrect, showing that we have also some other and more
reliable source of memory. Memory _may_ depend upon images, as in the
case mentioned above, of the house where I lived as a child. But it may
also be purely verbal. I am a poor visualiser, except for things I saw
before I was ten years old; when now I meet a man and wish to remember
his appearance, I find that the only way is to describe him in words
while I am seeing him, and then remember the words. I say to myself:
“This man has blue eyes and a brown beard and a small nose; he is
short, with a rounded back and sloping shoulders”. I can remember these
words for months, and recognise the man by means of them, unless two
men having these characteristics are present at once. In this respect,
a visualiser would have the advantage of me. Nevertheless, if I had
made my verbal inventory sufficiently extensive and precise, it would
have been pretty sure to answer its purpose. I do not think there is
anything in memory that absolutely demands images as opposed to words.
Whether the words we use in “thought” are themselves sometimes images
of words, or are always incipient movements (as Watson contends), is a
further question, as to which I offer no opinion, since it ought to be
capable of being decided experimentally.

The most important point about memory is one which has nothing to do
with images, and is not mentioned in Watson’s brief discussion. I mean
the reference to the past. This reference to the past is not involved
in mere habit memory, _e.g._ in skating or in repeating a poem formerly
learned. But it is involved in recollection of a past incident. We do
not, in this case, merely repeat what we did before: then, we felt the
incident as present, but now we feel it as past. This is shown in the
use of the past tense. We say to ourselves at the time “I _am having_ a
good dinner”, but next day we say “I _did have_ a good dinner”. Thus we
do not, like a rat in a maze, repeat our previous performance: we alter
the verbal formula. Why do we do so? What constitutes this reference of
a recollection to the past?[10]

     [10] On this subject, cf. Broad, _The Mind and Its Place in
          Nature_, p. 264 ff., in his chapter on “Memory”.

Let us take up the question first from the point of view of
sensitivity. The stimulus to a recollection is, no doubt, always
something in the present, but our reaction (or part of it) is more
intimately related to a certain past event than to the present
stimulus. This, in itself, can be paralleled in inanimate objects,
for example, in a gramophone record. It is not the _likeness_ of our
reaction to that called forth on a former occasion that concerns us
at the moment; it is its _un-likeness_, in the fact that now we have
the feeling of pastness, which we did not have originally. You cannot
sing into a dictaphone “I love you”, and have it say five days hence
“I loved you last Wednesday”; yet that is what we do when we remember.
I think, however, that this feature of memory is probably connected
with a feature of reactions due to association when the association
is cerebral: I think also that this is connected with the difference
in quality that exists usually, though not always, between images and
sensations. It would seem that, in such cases, the reaction aroused
through association is usually different from that which would have
been aroused directly, in certain definite ways. It is fainter, and
has, when attended to, the sort of quality that makes us call it
“imaginary”. In a certain class of cases, we come to know that we can
make it “real” if we choose; this applies, _e.g._ to the tactual images
produced by visible objects that we can touch. In such cases, the image
is attached by us to the object, and its “imaginary” character fails to
be noticed. These are the cases in which the association is not due to
some accident of our experience, but to a collocation which exists in
nature. In other cases, however, we are perfectly aware, if we reflect,
that the association depends upon some circumstance in our private
lives. We may, for instance, have had a very interesting conversation
at a certain spot, and always think of this conversation when we find
ourselves in this place. But we know that the conversation does not
actually take place again when we go back to where it happened. In
such a case, we notice the intrinsic difference between the event as
a sensible fact in the present and the event as merely revived by
association. I think this difference has to do with our feeling of
pastness. The difference which we can directly observe is not, of
course, between our present recollection and the past conversation,
but between our present recollection and present sensible facts. This
difference, combined with the inconsistency of our recollection with
present facts if our recollection were placed in the present, is
perhaps a cause of our referring memories to the past. But I offer this
suggestion with hesitation; and, as we shall find when we have examined
imagination, it cannot be the whole truth, though it may be part of it.

There are some facts that tend to support the above view. In dreams,
when our critical faculty is in abeyance, we may live past events
over again under the impression that they are actually happening; the
reference of recollections to the past must, therefore, be a matter
involving a somewhat advanced type of mental activity. Conversely,
we sometimes have the impression that what is happening now really
happened in the past; this is a well-known and much discussed illusion.
It happens especially when we are profoundly absorbed in some inward
struggle or emotion, so that outer events only penetrate faintly.
I suggest that, in these circumstances, the quality of sensations
approximates to that of images, and that this is the source of the
illusion.

If this suggestion is right, the feeling of pastness is really complex.
Something is suggested by association, but is recognisably different
from a present sensible occurrence. We therefore do not suppose that
this something is happening now; and we may be confirmed in this by
the fact that it is inconsistent with something that is happening now.
We may then either refer the something to the past, in which case we
have a recollection, though not necessarily a correct one; or we may
regard the something as purely imaginary, in which case we have what we
regard as pure imagination. It remains to inquire why we do sometimes
the one and sometimes the other, which brings us to the discussion of
imagination. I think we shall find that memory is more fundamental
than imagination, and that the latter consists merely of memories of
different dates assembled together. But to support this theory will
demand first an analysis of imagination and then, in the light of this
analysis, an attempt to give further precision to our theory of memory.

Imagination is not, as the word might suggest, essentially connected
with images. No doubt images are often, even usually, present when
we imagine, but they need not be. A man can improvise on the piano
without first having images of the music he is going to make; a poet
might write down a poem without first making it up in his head.
In talking, words suggest other words, and a man with sufficient
verbal associations may be successfully carried along by them for a
considerable time. The art of talking without thinking is particularly
necessary to public speakers, who must go on when once they are on
their feet, and gradually acquire the habit of behaving in private
as they do before an audience. Yet the statements they make must
be admitted to be often imaginative. The essence of imagination,
therefore, does not lie in images.

The essence of imagination, I should say, is the absence of belief
together with a novel combination of known elements. In memory, when
it is correct, the combination of elements is not novel; and whether
correct or not, there is belief. I say that in imagination there is “a
novel combination of known elements”, because, if nothing is novel,
we have a case of memory, while if the elements, or any of them,
are novel, we have a case of perception. This last I say because I
accept Hume’s principle that there is no “idea” without an antecedent
“impression”. I do not mean that this is to be applied in a blind and
pedantic manner, where abstract ideas are concerned. I should not
maintain that no one can have an idea of liberty until he has seen the
Statue of Liberty. The principle applies rather to the realm of images.
I certainly do not think that, in an image, there can be any element
which does not resemble some element in a previous perception, in the
distinctive manner of images.

Hume made himself an unnecessary difficulty in regard to the theory
that images “copy” impressions. He asked the question: Suppose a
man has seen all the different shades of colour that go to make up
the spectrum, except just one shade. To put the thing in modern
language, suppose he has never seen light of a certain small range of
wave-lengths, but has seen light of all other wave-lengths. Will he
be able to form an image of the shade he has never seen? Hume thinks
he will, although this contradicts the principle. I should say that
images are always more or less vague copies of impressions, so that an
image might be regarded as a copy of any one of a number of different
impressions of slightly different shades. In order to get a test
case for Hume’s question, we should have to suppose that there was a
broad band of the spectrum that the man had never seen--say the whole
of the yellow. He would then, one may suppose, be able to form images
which, owing to vagueness, might be applicable to orange-yellow, and
others applicable to green-yellow, but none applicable to a yellow
midway between orange and green. This is an example of an unreal puzzle
manufactured by forgetting vagueness. It is analogous to the following
profound problem: A man formerly hairy is now bald; he lost his hairs
one by one; therefore there must have been just one hair that made
the difference, so that while he had it he was not bald but when he
lost it he was. Of course “baldness” is a vague conception; and so
is “copying”, when we are speaking of the way in which images copy
prototypes.

What causes us, in imagination, to put elements together in a new way?
Let us think first of concrete instances. You read that a ship has
gone down on a route by which you have lately travelled; very little
imagination is needed to generate the thought “I might have gone
down”. What happens here is obvious: the route is associated both with
yourself and with shipwreck, and you merely eliminate the middle term.
Literary ability is largely an extension of the practice of which the
above is a very humble example. Take, say:

    And all our yesterdays have lighted fools
    The way to dusty death. Out, out, brief candle!
    Life’s but a walking shadow, a poor player
    Who struts and frets his hour upon the stage,
    And then is heard no more. It is a tale
    Told by an idiot, full of sound and fury
    Signifying nothing.

I do not pretend to explain all the associations which led Shakespeare
to think of these lines, but some few are obvious. “Dusty death” is
suggested by Genesis iii. 19: “Dust thou art, and unto dust shalt thou
return”. Having spoken of “lighting fools the way”, it is natural
to think of a “candle”, and thence of a “walking shadow” being
lighted by the candle along the way. From shadows to players was a
well-established association in Shakespeare’s mind; thus in _Midsummer
Night’s Dream_ he says of players: “The best in this kind are but
shadows, and the worst are no worse, if imagination amend them”. From
a “poor player” to a “tale told by an idiot” is no very difficult
transition for a theatre-manager; and “sound and fury” no doubt often
formed part of the tales to which he had to listen in spite of their
“signifying nothing”. If we knew more about Shakespeare, we could
explain more of him in this sort of way.

Thus exceptional imaginative gifts appear to depend mainly upon
associations that are unusual and have an emotional value owing to
the fact that there is a certain uniform emotional tone about them.
Many adjectives are suitable to death: in a mood quite different from
Macbeth’s, it may be called “noble, puissant and mighty”. A Chancellor
of the Exchequer, thinking of the Death Duties, might feel inclined to
speak of “lucrative death”; nevertheless he would not, like Vaughan,
speak of “dear, beauteous death”. Shakespeare also would not have
spoken of death in such terms, for his view of it was pagan; he speaks
of “that churl death”. So a man’s verbal associations may afford a key
to his emotional reactions, for often what connects two words in his
mind is the fact that they rouse similar emotions.

The absence of belief that accompanies imagination is a somewhat
sophisticated product; it fails in sleep and in strong and emotional
excitement. Children invent terrors for fun, and then begin to believe
in them. The state of entertaining an idea without believing it is one
involving some tension, which demands a certain level of intellectual
development. It may be assumed that imagination, at first, always
involved belief, as it still does in dreams. I am not concerned at the
moment to define “belief”, but a criterion is influence on action. If
I say “suppose there were a tiger outside your front door”, you will
remain calm; but if I say, with such a manner as to command belief,
“there is a tiger outside your front door”, you will stay at home, even
if it involves missing your train to the office. This illustrates what
I mean when I say that imagination, in its developed form, involves
absence of belief. But this is not true of its primitive forms. And
even a civilised adult, passing through a churchyard on a dark night,
may feel fear if his imagination turns in the direction of ghosts.

When imagination passes into belief, it does not, as a rule, become a
belief about the past. Generally we place the imagined object in the
present, but not where it would be perceptible to our senses. If we
place it in the past, it is because the past has some great emotional
significance for us. If a person we love has been in great danger,
and we do not know whether he has come through safely, imagination
of his death may lead us to believe that he has been killed. And
often imagination leads us to believe that something is going to
happen. What is common to all such cases is the emotional interest:
this first causes us to imagine an event, and then leads us to think
that it has happened, is happening, or will happen, according to the
circumstances. Hope and fear have this effect equally; wish-fulfilment
and dread-fulfilment are equally sources of dreams and day-dreams.
A great many beliefs have a source of this kind. But, in spite of
psycho-analysis, there are a great many that have a more rational
foundation. I believe that Columbus first crossed the ocean in 1492,
though 1491 or 1493 would have suited me just as well. I cannot
discover that there is any emotional element in this belief, or in the
belief that Semipalatinsk is in Central Asia. The view that all our
beliefs are irrational is perhaps somewhat overdone nowadays, though it
is far more nearly true than the views that it has displaced.

We must now return to the subject of memory. Memory proper does not,
like imagination, involve a re-arrangement of elements derived from
past experience; on the contrary, it should restore such elements
in the pattern in which they occurred. This is the vital difference
between memory and imagination; belief, even belief involving reference
to the past, may, as we have seen, be present in what is really
imagination though it may not seem to be so to the person concerned.
That being so, we still have to consider what constitutes the reference
to the past, since the view tentatively suggested before we had
considered imagination turns out to be inadequate.

There is one possible view, suggested, though not definitely adopted,
by Dr. Broad in his chapter on “Memory” already referred to. According
to this view, we have to start from temporal succession as perceived
within what is called the “specious present”, _i.e._ a short period of
time such that the events that occur throughout it can be perceived
together. (I shall return to this subject presently.) For example, you
can see a quick movement as a whole; you are not merely aware that
the object was first in one place and then in another. You can see
the movement of the second-hand of a watch, but not of the hour-hand
or minute-hand. When you see a movement in this sense, you are aware
that one part of it is earlier than another. Thus you acquire the idea
“earlier”, and you can mean by “past” “earlier than this”, where “this”
is what is actually happening. This is a logically possible theory,
but it seems nevertheless somewhat difficult to believe. I do not
know, however, of any easier theory, and I shall therefore adopt it
provisionally while waiting for something better.

For the understanding of memory, it is a help to consider the links
connecting its most developed forms with other occurrences of a less
complex kind. True recollection comes at the end of a series of stages.
I shall distinguish five stages on the way, so that recollection
becomes the sixth in gradual progress. The stages are as follows:

1. _Images._--As we have seen, images, at any rate in their simpler
parts, in fact copy past sensations more or less vaguely, even when
they are not known to do so. Images are “mnemic” phenomena, in the
sense that they are called up by stimuli formerly associated with their
prototypes, so that their occurrence is a result of past experience
according to the law of association. But obviously an image which in
fact copies a past occurrence does not constitute a recollection unless
it is _felt_ to be a copy.

2. _Familiarity._--Images and perceptions may come to us, and so may
words or other bodily movements, with more or less of the feeling we
call “familiarity”. When you recall a tune that you have heard before,
either by images or by actually singing it, part of what comes to you
may feel familiar, part unfamiliar. This may lead you to judge that
you have remembered the familiar part rightly and the unfamiliar part
wrongly, but this judgment belongs to a later stage.

3. _Habit-Memory._--We have already discussed this in Chapter VI.
People say they remember a poem if they can repeat it correctly.
But this does not necessarily involve any recollection of a past
occurrence; you may have quite forgotten when and where you read the
poem. This sort of memory is mere habit, and is essentially like
knowing how to walk although you cannot remember learning to walk. This
does not deserve to be called memory in the strict sense.

4. _Recognition._--This has two forms. (_a_) When you see a dog, you
can say to yourself “there is a dog”, without recalling any case in
which you have seen a dog before, and even without reflecting that
there have been such cases. This involves no knowledge about the past;
essentially it is only an associative habit. (_b_) You may know “I
saw this before”, though you do not know when or where, and cannot
recollect the previous occurrence in any way. In such a case there is
knowledge about the past, but it is very slight. When you judge: “I saw
_this_ before”, the word “this” must be used vaguely, because you did
not see exactly what you see now, but only something very like this.
Thus all that you are really knowing is that, on some past occasion,
you saw something very like what you are seeing now. This is about the
minimum of knowledge about the past that actually occurs.

5. _Immediate Memory._--I come now to a region intermediate between
sensation and true memory, the region of what is sometimes called
“immediate memory”. When a sense-organ is stimulated, it does not,
on the cessation of the stimulus, return at once to its unstimulated
condition: it goes on (so to speak) vibrating, like a piano-string,
for a short time. For example, when you see a flash of lightning, your
sensation, brief as it is, lasts much longer than the lightning as a
physical occurrence. There is a period during which a sensation is
fading: it is then called an “acoleuthic” sensation. It is owing to
this fact that you can see a movement as a whole. As observed before,
you cannot see the minute-hand of a watch moving, but you can see
the second-hand moving. That is because it is in several appreciably
different places within the short time that is required for one visual
sensation to fade, so that you do actually, at one moment, see it in
several places. The fading sensations, however, feel different from
those that are fresh, and thus the various positions which are all
sensibly present are placed in a series by the degree of fading, and
you acquire the perception of movement as a process. Exactly the same
considerations apply to hearing a spoken sentence.

Thus not only an instant, but a short finite time is sensibly present
to you at any moment. This short finite time is called the “specious
present”. By the felt degree of fading, you can distinguish earlier and
later in the specious present, and thus experience temporal succession
without the need of true memory. If you see me quickly move my arm from
left to right, you have an experience which is quite different from
what you would have if you now saw it at the right and remembered that
a little while ago you saw it at the left. The difference is that, in
the quick movement, the whole falls within the specious present, so
that the entire process is sensible. The knowledge of something as
in the immediate past, though still sensible, is called “immediate
memory”. It has great importance in connection with our apprehension of
temporal processes, but cannot count as a form of true memory.

6. _True Recollection._--We will suppose, for the sake of definiteness,
that I am remembering what I had for breakfast this morning. There
are two questions which we must ask about this occurrence: (_a_) What
is happening now when I recollect? (_b_) What is the relation of the
present happening to the event remembered? As to what is happening now,
my recollection may involve either images or words; in the latter case,
the words themselves may be merely imagined. I will take the case in
which there are images without words, which must be the more primitive,
since we cannot suppose that memory would be impossible without words.

The first point is one which seems so obvious that I should be ashamed
to mention it, but for the fact that many distinguished philosophers
think otherwise. The point is this: whatever may be happening now, the
event remembered is _not_ happening. Memory is often spoken of as if
it involved the actual persistence of the past which is remembered;
Bergson, _e.g._ speaks of the interpenetration of the present by the
past. This is mere mythology; the event which occurs when I remember
is quite different from the event remembered. People who are starving
can remember their last meal, but the recollection does not appease
their hunger. There is no mystic survival of the past when we remember;
merely a new event having a certain relation to the old one. What this
relation is, we shall consider presently.

It is quite clear that images are not enough to constitute
recollection, even when they are accurate copies of a past occurrence.
One may, in a dream, live over again a past experience; while one is
dreaming, one does not seem to be recalling a previous occurrence, but
living through a fresh experience. We cannot be said to be remembering,
in the strict sense, unless we have a belief referring to the past.
Images which, like those in dreams, feel as if they were sensations,
do not constitute recollection. There must be some feeling which makes
us refer the images to a past prototype. Perhaps familiarity is enough
to cause us to do so. And perhaps this also explains the experience of
trying to remember something and feeling that we are not remembering
it right. Parts of a complex image may feel more familiar than other
parts, and we then feel more confidence in the correctness of the
familiar parts than in that of the others. The conviction that the
image we are forming of a past event is wrong might _seem_ to imply
that we must be knowing the past otherwise than by images, but I do not
think this conclusion is really warranted, since degrees of familiarity
in images suffice to explain this experience.

(_b_) What is the relation of the present happening to the event
remembered? If we recollect correctly, the several images will have
that kind of resemblance of quality which images can have to their
prototypes, and their structure and relations will be identical with
those of their prototypes. Suppose, for instance, you want to remember
whether, in a certain room, the window is to the right or left of the
door as viewed from the fireplace. You can observe your image of the
room, consisting (_inter alia_) of an image of the door and an image
of the window standing (if your recollection is correct) in the same
relation as when you are actually seeing the room. Memory will consist
in attaching to this complex image the sort of belief that refers to
the past; and the correctness of memory consists of similarity of
quality and identity of structure between the complex image and a
previous perception.

As for the trustworthiness of memory, there are two things to be said.
Taken as a whole, memory is one of the independent sources of our
knowledge; that is to say, there is no way of arriving at the things we
know through memory by any argument wholly derived from things known
otherwise. But no single memory is obliged to stand alone, because it
fits, or does not fit, into a system of knowledge about the past based
upon the sum-total of memories. When what is remembered is a perception
by one or more of the public senses, other people may corroborate it.
Even when it is private, it may be confirmed by other evidence. You
may remember that you had a toothache yesterday, and that you saw
the dentist to-day; the latter fact may be confirmed by an entry in
your diary. All these make a consistent whole, and each increases the
likelihood of the other. Thus we can test the truth of any particular
recollection, though not of memory as a whole. To say that we cannot
test the truth of memory as a whole is not to give a reason for
doubting it, but merely to say that it is an independent source of
knowledge, not wholly replaceable by other sources. We know that our
memory is fallible, but we have no reason to distrust it on the whole
after sufficient care in verification has been taken.

The causation of particular acts of recollection seems to be wholly
associative. Something in the present is very like something in the
past, and calls up the context of the past occurrence in the shape of
images or words; when attention falls upon this context, we believe
that it occurred in the past, not as mere images, and we then have an
act of recollection.

There are many difficult problems connected with memory which I have
not discussed, because they have an interest which is more purely
psychological than philosophical. It is memory as a source of knowledge
that specially concerns the philosopher.




CHAPTER XIX

THE INTROSPECTIVE ANALYSIS OF PERCEPTION


We have considered perception already from the behaviourist standpoint,
and also from that of physics. In the present chapter we are to
consider it from the standpoint of self-observation, with a view to
discovering as much as we can about the intrinsic character of the
event in us when we perceive. I shall begin with certain traditional
doctrines as to mental events, and shall thence pass to the doctrines
that I wish to advocate.

The words “mind” and “matter” are used glibly, both by ordinary people
and by philosophers, without any adequate attempt at definition.
Philosophers are much to blame for this. My own feeling is that there
is not a sharp line, but a difference of degree; an oyster is less
mental than a man, but not wholly un-mental. And I think “mental” is a
character, like “harmonious” or “discordant”, that cannot belong to a
single entity in its own right, but only to a system of entities. But
before defending this view, I wish to spend some time on the theories
that have been current in the past.

Traditionally, there are two ways of becoming aware that something
exists, one by the senses, the other by what is called “introspection”,
or what Kant called the “inner sense”. By means of introspection, it is
maintained, we become aware of occurrences quite different in kind from
those perceived through the outer senses. Occurrences known through
introspection are traditionally called “mental”, and so are any other
occurrences which intrinsically resemble them.

Mental occurrences are traditionally of three main types, called
knowing, willing, and feeling. “Feeling”, in this connection, means
pleasure and unpleasure--we do not say “pleasure and pain”, because
“pain” is an ambiguous word: it may stand for painful sensation, as
when you say “I have a pain in my tooth”, or it may stand for the
unpleasant character of the sensation. Roughly pleasure is a quality
which makes you want an experience to continue, and unpleasure is the
opposite quality which makes you want an experience to stop. However, I
am not concerned to enlarge upon feeling at present.

As for the other two kinds of mental occurrence, “knowing” and
“willing” are recognised as too narrow to describe what is meant.
Philosophers wish to include not only knowledge but also error, and
not only the sort of knowledge that is expressed in beliefs but also
the sort that occurs in perception. The word “cognition” or “cognitive
state” is used to cover everything that could possibly be described as
either knowledge or error; perception is _prima facie_ included, but
pure sensation is more debatable.

“Willing”, again, is too narrow a term. A term is required which will
include desire and aversion, and generally those states of mind which
lead up to action. These are all included under the head of “conation”,
a technical term invented for this special purpose.

Cognition and conation both have, in the orthodox theory, the property
of being directed to an _object_. What you perceive or believe, what
you desire or will, is something different from your state of mind. To
take instances: you remember a past event, but your remembering occurs
now; therefore your remembering is a different occurrence from what you
remember. You will to move your arm, but the movement is a physical
occurrence, and therefore obviously different from your volition. Many
psychologists have taken this relation to an object as the essential
characteristic of mind--notably the two Austrians Brentano and Meinong.
Sometimes feeling also is regarded as having an object: it is held
that we are pleased or displeased _at_ something. This view, however,
has never won general acceptance, whereas the view that cognition and
conation are directed to objects may be regarded as orthodox.

It is undeniable that this characteristic of being directed to objects
is, in some sense, a property of cognition and conation, but there
is room for great difference of opinion as to the proper analysis of
the property. I think we cannot hope to understand the word “mental”
until we have undertaken this analysis, and I shall therefore proceed
to address myself to it. I shall confine myself to cognition, which is
more important for our present purposes than conation.

As regards cognition, though philosophers have disagreed widely, I
think that, until recently, most would have assented to at least the
following paragraph:

Cognition is of various sorts. Take, as important kinds, perception,
memory, conception, and beliefs involving concepts. Perception is the
ordinary awareness of sensible objects: seeing a table, hearing a
piano, and so on. Memory is awareness of a past occurrence, when this
awareness is direct, not inferred or derived from testimony. Conception
is more difficult to characterise. One may say, as a way of pointing
out what is intended, that we “conceive” whenever we understand the
meaning of an abstract word, or think of that which is in fact the
meaning of the word. If you see a white patch of snow, or recall it
by means of images, you do not have a concept; but if you think about
whiteness, you have a concept. Similarly if, after seeing a number of
coins, you think about roundness as a common characteristic of all of
them, you have a concept. The object of your thought, in such a case,
is a _universal_ or a Platonic idea. Every sentence must contain at
least one word expressing a concept, and therefore every belief that
can be expressed in words contains concepts.

Each of these kinds of cognitive attitude involves its own problems.
In the present chapter we are concerned with perception. This has to
be treated both introspectively and causally; it is the introspective
treatment that we have now to undertake.

When you have the experience called “seeing a table”, there is a
certain amount of difference between your unreflecting judgment and
what careful examination reveals as to the nature of your experience.
You judge that the table is rectangular, but the patch of colour in
your visual field is not a rectangle; when you learn to draw, you have
to draw the table as it really seems and not as it seems to seem. You
have images of sensations of touch; if you were to try to touch the
table and it turned out to be an optical illusion, you would get a
violent shock of surprise. You have also expectations of a certain
degree of permanence and weight. If you went to lift the table, you
would find your muscles quite wrongly adjusted if the table were much
lighter than it looked. All these elements must be included in the
perception, though not in the sensation.

“Sensation”, as opposed to perception, is more or less hypothetical.
It is supposed to be the core, in the perception, which is solely due
to the stimulus and the sense-organ, not to past experience. When
you judge that the table is rectangular, it is past experience that
enables and compels you to do so; if you had been born blind and just
operated upon, you could not make this judgment. Nor would you have
expectations of hardness, etc. But none of this can be discovered by
introspection. From an introspective point of view, the elements due
to past experience are largely indistinguishable from those due to the
stimulus alone. One supposes that past experience modifies the brain,
and thereby modifies the mental occurrence due to the stimulus. The
notion of sensation as opposed to perception belongs, therefore, to the
causal study of perception, not to the introspective study.

There is, however, a distinction to be made here. You can discover
by mere self-observation that visual objects are accompanied by
expectations or images of touch; and similarly if you touch an object
in the dark you will probably be led to form some visual image of
it. Here you can arrive at a certain degree of analysis of your
perception through the fact that images, as a rule, _feel_ different
from the immediate results of a sensory stimulus. On the other hand,
no amount of introspection alone will reveal such things as the blind
spot. The filling in of a sensation by elements belonging to the same
sense is much less discoverable by introspection than the filling
in by associated images belonging to other senses. Thus although
by introspection alone we could discover _part_ of the influence
of experience on perception, there is another part which we cannot
discover in this way.

Remaining in the introspective attitude, it is evident that the
contents of our minds at any given moment are very complex. Throughout
our normal waking life we are always seeing, hearing, and touching,
sometimes smelling and tasting, always having various bodily
sensations, always feeling pleasant or unpleasant feelings (usually
both), always having desires or aversions. We are not normally aware
of all these items, but we can become aware of any of them by turning
our attention in the right direction. I am not at present discussing
“unconscious mental states”, because they, obviously, can only be known
causally, and we are now considering what can be known introspectively.
There may be any number of perceptions that cannot be known by
introspection; the point for us, at the moment, is that those that can
be discovered by introspection at any one time are many and various.

I do not wish, just now, to discuss the nature of attention; I wish
only to point out that it enables us to take the first steps in
abstraction. Out of the whole multiplicity of objects of sense, it
enables us to single out a small selection, which is an indispensable
preliminary to abstraction. For example, attention will enable us to
discriminate a coloured pattern which we are seeing, and to separate
it from the other things we see and from images and other objects of
sense and thoughts which may exist simultaneously. For the sake of
simplicity, let us suppose that we discriminate a black and white
pattern in the form of a triangle. Within this pattern we can further
discriminate sides and angles and an inside and outside--of course the
sides are not mathematical lines nor the angles mathematical points.

We now come to a question of very great importance, upon which our
views of the relations of mind and matter largely depend. The question
is this:

What difference is there between the propositions “there is a triangle”
and “I see a triangle”?

Both these statements seem as certain as any statement can be--at least
if rightly interpreted. As always happens in such cases, we are quite
certain of something, but not quite certain what it is that we are
certain of. I want to ask whether this something that we are certain
of is really different in the above two statements, or whether the
difference between them is only as to surroundings of which we are not
certain. Most philosophers hold that there is a difference in what we
are certain of; Mach, James, Dewey, the American realists, and I hold
that the difference is in the uncertain context. Let us examine this
question.

The _suggestions_ of the two statements “I see a triangle” and “there
is a triangle” are obviously different. The first states an event in
my life, and suggests its possible effects upon me. The second aims at
stating an event in the world, supposed to be equally discoverable by
other people. You might say “there is a triangle” if you had seen it
a moment ago but now had your eyes shut; in this case you would not
say “I see a triangle”. On the other hand, one sometimes, under the
influence of indigestion or fatigue, sees little black dots floating in
the air; in such circumstances you would say “I see a black dot”, but
not “there is a black dot”. This illustration shows that when you say
“there is a black dot” you are making a stronger assertion than when
you say “I see a black dot”. In the other case, when you say “there is
a triangle” because you saw it a moment ago, though not now, you have
three stages: First, memory assures you of the proposition “I saw a
triangle”, and then you pass on to “there was a triangle”, and then,
further, to “there is a triangle, because nothing can have happened to
destroy it so quickly.” Here we have obviously passed far beyond the
region of immediate certainty.

It seems clear, therefore, that, of our two statements, the one which
comes nearest to expressing the fact of which we are immediately
certain is “I see a triangle”, because the other makes inferences to
something public, and thus goes beyond the bare datum. This is on the
assumption that we should not say “there is a black dot” when we see
a black dot which we attribute to eye-trouble and therefore suppose
that no one else can see. Let us therefore concentrate upon “I see a
triangle”, and ask ourselves whether the whole of this, or only part,
can be accepted as a primitive certainty.

A moment’s reflection shows that both “I” and “see” are words which
take us beyond what the momentary event reveals. Take “I” to begin
with. This is a word whose meaning evidently depends upon memory
and expectation. “I” means the person who had certain remembered
experiences and is expected to have certain future experiences. We
might say “I see a triangle now and I saw a square a moment ago.” The
word “I” has exactly the same meaning in its two occurrences in this
sentence, and therefore evidently has a meaning dependent upon memory.
Now it is our object to arrive at the contribution to your knowledge
which is made by seeing the triangle at the moment. Therefore, since
the word “I” takes you beyond this contribution, we must cut it out
if we want to find a correct verbal expression for what is added to
our knowledge by seeing the triangle. We will say “a triangle is being
seen”. This is at any rate one step nearer to what we are seeking.

But now we must deal with the word “seen”. As ordinarily used, this is
a causal word, suggesting something dependent upon the eyes. In this
sense, it obviously involves a mass of previous experience; a new-born
baby does not know that what it sees depends upon its eyes. However,
we could eliminate this. Obviously all objects of sight have a common
quality, which no objects of touch or hearing have; a visual object is
different from an auditory object, and so on. Therefore instead of
saying “a triangle is being seen”, we should say “there is a visual
triangle”. Of course the meanings of the words “visual” and “triangle”
can only be learnt by experience, but they are not _logically_
dependent upon experience. A being could be imagined which would know
the words at birth; such a being could express its datum in the words
“there is a visual triangle”. In any case, the problems remaining
belong to the study of concepts; we will therefore ignore them at
present.

Now in English the words “there is” are ambiguous. When I used them
before, saying, “there is a triangle”, I meant them in the sense of
“_voila_” or “_da ist_”. Now I mean them in the sense of “_il y a_”
or “_es giebt_”. One might express what is meant by saying “a visual
triangle exists”, but the word “exist” has all sorts of metaphysical
connotations that I wish to avoid. Perhaps it is best to say “occurs”.

We have now arrived at something which is just as true when your
perception is illusory as when it is correct. If you say “a visual
black dot is occurring”, you are speaking the truth, if there is one
in your field of vision. We have eliminated the suggestion that others
could see it, or that it could be touched, or that it is composed of
matter in the sense of physics. All these suggestions are present when
one says, in ordinary conversation, “there is a black dot”; they are
intended to be eliminated by the addition of the word “visual” and the
substitution of “is occurring” for “there is”. By these means we have
arrived at what is indubitable and intrinsic in the addition to your
knowledge derived from a visual datum.

We must now ask ourselves once more: Is there still a distinction,
within what is immediate and intrinsic, between the occurrence of a
visual datum and the cognition of it? Can we say, on the basis of
immediate experience, not only “a visual black dot occurs”, but also
“a visual black dot is cognised”? My feeling is that we cannot. When
we say that it is cognised, we seem to me to mean that it is part
of an experience, that is to say, that it can be remembered, or can
modify our habits, or, generally, can have what are called “mnemic”
effects. All this takes us beyond the immediate experience into the
realm of its causal relations. I see no reason to think that there is
any duality of subject and object in the occurrence itself, or that
it can properly be described as a case of “knowledge”. It gives rise
to knowledge, through memory, and through conscious or unconscious
inferences to the common correlates of such data. But in itself it
is not knowledge, and has no duality. The datum is a datum equally
for physics and for psychology; it is a meeting point of the two. It
is neither mental nor physical, just as a single name is neither in
alphabetical order nor in order of precedence; but it is part of the
raw material of both the mental and the physical worlds. This is the
theory which is called “neutral monism”, and is the one that I believe
to be true.




CHAPTER XX

CONSCIOUSNESS?


Twenty-three years have elapsed since William James startled the
world with his article entitled “Does ‘consciousness’ exist?” In this
article, reprinted in the volume called _Essays in Radical Empiricism_,
he set out the view that “there is only one primal stuff or material in
the world”, and that the word “consciousness” stands for a function,
not an entity. He holds that there are “thoughts”, which perform the
function of “knowing”, but that thoughts are not made of any different
“stuff” from that of which material objects are made. He thus laid
the foundations for what is called “neutral monism”, a view advocated
by most American realists. This is the view advocated in the present
volume. In this chapter, we have to ask ourselves whether there is
anything that we can call “consciousness” in any sense involving a
peculiar kind of stuff, or whether we can agree with William James that
there is no “inner duplicity” in the stuff of the world as we know it,
and that the separation of it into knowing and what is known does not
represent a fundamental dualism.

There are two very different meanings attached to the word
“consciousness” by those who use it. On the one hand, we are said to be
“conscious of” something; in this sense, “consciousness” is a relation.
On the other hand, “consciousness” may be regarded as a quality of
mental occurrences, not consisting in their relation to other things.
Let us take the first view first, since, in discussing it, we shall
find reasons for rejecting the second view.

What is the relation we call being “conscious of” something? Take the
difference between a person awake and a person asleep. The former
reacts to all kinds of stimuli to which the latter does not react; we
therefore say that the latter is not “conscious of” what is happening
in his neighbourhood. But even if the sleeper does react in a fashion,
for example, by turning away from the light, such a reaction does not
fall within what is commonly regarded as “knowledge” or “awareness”; we
should say that the sleeper turned over “unconsciously”. If he wakes
up sufficiently to speak intelligently, for instance to address the
disturber by name, we consider him “conscious”. So we do if we find
that he remembers the incident next morning. But common sense does
not regard any and every bodily movement in response to a stimulus as
evidence of “consciousness”. There is no doubt, I think, that common
sense regards certain kinds of response as evidence of some “mental”
process caused by the stimulus, and regards the “consciousness” as
residing in the inferred “mental” occurrence.

Sometimes, however, as in hypnotism and sleep-walking, people refuse
to admit “consciousness” even where many of the usual marks of it are
present. For this there are certain reasons. One of them is subsequent
lack of memory; another is lack of intelligence in what is being done.
If you offer a hypnotised patient a drink of ink, telling him it is
port wine, and he drinks it up with every sign of enjoyment, you say
that he is not “conscious”, because he does not react normally to
the nasty taste. It would seem better, however, to say that he is
conscious of the hypnotist and what he commands, though not of other
things of which he would be conscious in a normal condition. And lack
of subsequent memory is a very difficult criterion, since we normally
forget many things that have happened to us, and the sleep-walker’s
forgetting is only unusually complete. This is obviously a matter of
degree. Take next morning’s memories in the case of a man who was drunk
overnight. They become more and more vague as he reviews the later
hours of the evening, but there is no sharp line where they cease
abruptly. Thus, if memory is a test, consciousness must be a matter of
degree. I think that here, again, common sense regards a certain amount
of memory as necessary evidence to prove that there were “mental”
processes at the time of the acts in question, acts in sleep being
regarded as not involving “mind”, and other acts in certain abnormal
conditions being supposed to resemble those of sleep in this respect.

It follows that, if we are to find out what is commonly meant by
“consciousness”, we must ask ourselves what is meant by a “mental”
occurrence. Not every mental occurrence, however, is in question.
The only kinds concerned are those which seem to have relation to an
“object”. A feeling of pleasant drowsiness would commonly count as
“mental”, but does not involve “consciousness” of an “object”. It is
this supposed peculiar relation to an “object” that we have to examine.

We may take, as the best example, an ordinary act of perception. I
see, let us say, a table, and I am convinced that the table is outside
me, whereas my seeing of it is a “mental” occurrence, which is inside
me. In such a case I am “conscious” of the table--so at least common
sense would say. And since I cannot see without seeing something, this
relation to an “object” is of the very essence of seeing. The same
essential relation to an “object”, it would be said, is characteristic
of every kind of consciousness.

But when we begin to consider this view more closely, all sorts of
difficulties arise. We have already seen that, on grounds derived from
physics, the table itself, as a physical thing, cannot be regarded as
the object of our perception, if the object is something essential to
the existence of the perception. In suitable circumstances, we shall
have the same perception although there is no table. In fact, there
is no event outside the brain which _must_ exist whenever we “see
a table”. It seems preposterous to say that when we think we see a
table we really see a motion in our own brain. Hence we are led to the
conclusion that the “object” which is essential to the existence of
an act of perception is just as “mental” as the perceiving. In fact,
so this theory runs, the mental occurrence called “perceiving” is one
which contains within itself the relation of perceiver and perceived,
both sides of the relation being equally “mental”.

Now, however, there seems no longer any reason to suppose that there is
any essentially relational character about what occurs in us when we
perceive. The original reason for thinking so was the naively realistic
view that we see the actual table. If what we see is as mental as our
seeing, why distinguish between the two? The coloured pattern that
we see is not really “out there”, as we had supposed; it is in our
heads, if we are speaking of physical space. True, more than a coloured
pattern occurs when we “see a table”. There are tactual expectations or
images: there is probably belief in an external object; and afterwards
there may be memory or other “mnemic” effects. All this may be taken as
representing what the above theory took to be the “subject” side of an
act of perception, while the coloured pattern is what the theory took
to be the “object” side. But both sides are on a level as regards being
“mental”. And the relation between the two sides is not of such a kind
that the existence of the one logically demands the existence of the
other; on the contrary, the relation between the two sides is causal,
being dependent upon experience and the law of association.

If this is correct, what really happens when, as common sense would
say, we are conscious of a table, is more or less as follows. First
there is a physical process external to the body, producing a stimulus
to the eye which occurs rarely (not never) in the absence of an actual
physical table. Then there is a process in the eye, nerves, and brain,
and finally there is a coloured pattern. This coloured pattern, by the
law of association, gives rise to tactual and other expectations and
images; also, perhaps, to memories and other habits. But everything in
this whole series consists of a causally continuous chain of events
in space-time, and we have no reason to assert that the events in us
are so very different from the events outside us--as to this, we must
remain ignorant, since the outside events are only known as to their
abstract mathematical characteristics, which do not show whether these
events are like “thoughts” or unlike them.

It follows that “consciousness” cannot be defined either as a
peculiar kind of relation or as an intrinsic character belonging to
certain events and not to others. “Mental” events are not essentially
relational, and we do not know enough of the intrinsic character of
events outside us to say whether it does or does not differ from that
of “mental” events. But what makes us call a certain class of events
“mental” and distinguish them from other events is the combination
of sensitivity with associative reproduction. The more markedly this
combination exists, the more “mental” are the events concerned; thus
mentality is a matter of degree.

There is, however, a further point which must be discussed in this
connection, and that is “self-consciousness”, or awareness of our own
“mental” events. We already had occasion to touch on this in Chapter
XVI in connection with Descartes’ “I think, therefore I am”. But I want
to discuss the question afresh in connection with “consciousness”.

When the plain man sees “a table” in the presence of a philosopher, the
plain man can be driven, by the arguments we have repeatedly brought
forward, to admit that he cannot have complete certainty as to anything
outside himself. But if he does not lose his head or his temper, he
will remain certain that there is a coloured pattern, which may be in
him, but indubitably exists. No argument from logic or physics even
tends to show that he is mistaken in this; therefore there is no reason
why he should surrender his conviction. The argument about knowledge
in Chapter VIII showed that, accepting the usual views of physicists
as to causal laws, our knowledge becomes more certain as the causal
chain from object to reaction is shortened, and can only be quite
certain when the two are in the same place in space-time, or at least
contiguous. Thus we should expect that the highest grade of certainty
would belong to knowledge as to what happens in our own heads. And this
is exactly what we have when we are aware of our own “mental” events,
such as the existence of a coloured pattern when we thought we were
seeing a table.

We might, therefore, if we were anxious to preserve the word “mental”,
define a “mental” event as one that can be known with the highest
grade of certainty, because, in physical space-time, the event and the
knowing of it are contiguous. Thus “mental” events will be certain of
the events that occur in heads that have brains. They will not be _all_
events that occur in brains, but only such as cause a reaction of the
kind that can be called “knowledge”.

There are, however, still a number of difficult questions, to which, as
yet, a definitive answer cannot be given. When we “know” a thought of
our own, what happens? And do we know the thought in a more intimate
way than we know anything else? Knowledge of external events, as we
have seen, consists of a certain sensitivity to their presence, but
not in having in or before our minds anything similar to them, except
in certain abstract structural respects. Is knowledge of our own minds
equally abstract and indirect? Or is it something more analogous to
what we ordinarily imagine knowledge to be?

Take first the question: What happens when we “know” a thought of our
own? Taking the definition of “knowing” that we adopted in Chapter
VIII, we shall say: We “know” a thought of our own when an event in
our brain causes a characteristic reaction which is present when the
event occurs and not otherwise. In this sense, whenever we say, “I see
a table”, we are knowing a thought, since an event in our brain is the
only invariable antecedent of such a statement (assuming it to be made
truthfully). We may _think_ we are knowing a table, but this is an
error.

Thus the difference between introspective and other knowledge is only
in our intention and in the degree of certainty. When we say, “I see a
table”, we may intend to know an external object, but if so we may be
mistaken; we are, however, actually knowing the occurrence of a visual
percept. When we describe the same occurrence in the words “a certain
coloured pattern is occurring”, we have changed our intention and are
much more certain of being right. Thus all that differentiates our
reaction when it gives introspective knowledge from our reaction when
it gives knowledge of another kind is the elimination of a possible
source of error.

I come now to the question: Do we know our own thoughts in a more
intimate way than we know anything else? This is a question to which it
is difficult to give precision; it describes something that one _feels_
to be a problem without being able to say exactly what the problem
is. However, some things can be said which may serve to clear up our
feelings, if not our ideas.

Suppose you are asked to repeat after a man whatever he says, as a
test of your hearing. He says “how do you do?” and you repeat “how
do you do?” This is your knowledge-reaction, and you hear yourself
speaking. You can perceive that what you hear when you speak is
closely similar to what you hear when the other man speaks. This makes
you feel that your reaction reproduces accurately what you heard.
Your knowledge-reaction, in this case, is the cause of an occurrence
closely similar to the occurrence that you are knowing. Moreover, our
inveterate naive realism makes us think that what we said was what we
heard while we were speaking. This is, of course, an illusion, since
an elaborate chain of physical and physiological causation intervenes
between speaking and hearing oneself speak; nevertheless, the illusion
re-enforces our conviction that our knowledge, in such a case, is very
intimate. And it is, in fact, as intimate as it can hope to be, when
our knowledge-reaction reproduces the very event we are knowing, or
at least an event extremely similar to it. This _may_ be the case on
other occasions, but we can only know, with any certainty, that it
is the case when what is known is a percept. This accounts for the
fact that our most indubitable and complete knowledge is concerning
percepts, not concerning other mental events or events in the external
world. Our reaction to a sound can be to make a similar sound, and if
we are clever enough we can paint something very like what we see. But
we cannot show our knowledge of a pleasure by creating for ourselves
another very similar pleasure, nor of a desire by creating a similar
desire. Thus percepts are known with more accuracy and certainty than
anything else either in the outer world or in our own minds.

The conclusion we have reached in this chapter is that William James
was right in his views on “consciousness”. No mental occurrence has,
in its own intrinsic nature, that sort of relational character that
was implied in the opposition of subject and object, or of knower and
known. Nevertheless we can distinguish “mental” events from others,
and our most indubitable knowledge is concerned with a certain class
of mental events. We have arrived at this result by following out to
its logical conclusion the behaviourist definition of knowledge which
we gave in Chapter VIII. We have had to modify considerably the point
of view which originally led us to that definition, the modification
having been forced upon us by the physical knowledge which, starting
from a common-sense realism, has been gradually driven, through the
causal theory of perception, to a view of cognition far more subjective
than that from which physicists, like the rest of mankind, originally
set out. But I do not see how there can be any escape from this
development.




CHAPTER XXI

EMOTION, DESIRE, AND WILL


Hitherto, in our investigation of man from within, we have considered
only the cognitive aspect, which is, in fact, the most important to
philosophy. But now we must turn our attention to the other sides of
human nature. If we treat them more briefly than the cognitive side,
it is not because they are less important, but because their main
importance is practical and our task is theoretical. Let us begin with
the emotions.

The theory of the emotions has been radically transformed by the
discovery of the part played by the ductless glands. Cannon’s _Bodily
Changes in Pain, Hunger, Fear and Rage_ is a book whose teaching
has come to be widely known, though not more so than its importance
warrants. It appears that certain secretions from the glands into the
blood are the essential physiological conditions of the emotions.
Some people say that the physiological changes correlated with these
secretions _are_ the emotions. I think this view must be received with
some caution. As everyone knows, the adrenal glands secrete adrenin,
which produces the bodily symptoms of fear or rage. On one occasion my
dentist injected a considerable amount of this substance into my blood,
in the course of administering a local anæsthetic. I turned pale and
trembled, and my heart beat violently; the bodily symptoms of fear were
present, as the books said they should be, but it was quite obvious to
me that I was not actually feeling fear. I should have had the same
bodily symptoms in the presence of a tyrant about to condemn me to
death, but there would have been something extra which was absent when
I was in the dentist’s chair. What was different was the cognitive
part: I did not feel fear because I knew there was nothing to be afraid
of. In normal life, the adrenal glands are stimulated by the perception
of an object which is frightful or enraging; thus there is already a
cognitive element present. The fear or rage attaches itself to the
object which has stimulated the glands, and the full emotion arises.
But when adrenin is artificially administered, this cognitive element
is absent, and the emotion in its entirety fails to arise. Probably if
it were administered in sleep it would produce a dream of terror, in
which the dreamer’s imagination would supply an object for fear. The
same thing might happen on waking life with animals or young children.
But with an adult of average rationality, the knowledge that there is
nothing to be afraid of inhibits the full development of the emotion.
Fear and rage are both active emotions, demanding a certain kind of
behaviour towards an object; when this behaviour is obviously not
called for, it is impossible to feel either emotion fully.

There are, however, other emotions, such as melancholy, which do not
demand an object. These, presumably, can be caused in their entirety
by administering the proper secretions. A disordered liver may cause
melancholy which is not relieved by knowledge of its source. The
emotions which do not require an object are those which do not call for
any appropriate line of action.

Emotions are subject to “conditioning”, so that the stimuli which call
them out become more various as a result of experience. Dr. Watson has
found only two original stimuli to fear in young infants, namely loud
noises, and lack of support; but anything associated with either of
these may become terrifying.

The separation of an emotional element in our integral reaction to a
situation is more or less artificial. No doubt there is a definite
physiological concomitant, namely stimulation of a gland; but fear,
for example, involves a mode of action towards an object, for which
mode of action the secretion of adrenin is helpful. There is,
however, something in common among a number of occasions that have a
given emotional tone; this may be seen from the fact that they are
associated. When we are feeling some emotion strongly, we tend to think
of other occasions when we have had similar feelings. Association by
means of emotional similarity is a characteristic of a great deal of
poetry. And this accounts for the fact that, if our blood is in a state
usually associated with terror, we shall, if our critical faculty is in
abeyance, be very likely to imagine some cause of fear so vividly as to
believe that it is really present:

    In the night, imagining some fear,
    How easy is a bush supposed a bear.

But in a rational man, if he is not drunk or sleepy, other associations
are too strong for this production of imaginary terrors. That is why it
is possible to show the physical symptoms of fear under the influence
of adrenin, without actually feeling the emotion.

The emotions are what makes life interesting, and what makes us feel it
important. From this point of view, they are the most valuable element
in human existence. But when, as in philosophy, we are trying to
understand the world, they appear rather as a hindrance. They generate
irrational opinions, since emotional associations seldom correspond
with collocations in the external world. They cause us to view the
universe in the mirror of our moods, as now bright, now dim, according
to the state of the mirror. With the sole exception of curiosity, the
emotions are on the whole a hindrance to the intellectual life, though
the degree of vigour required for successful thinking is likely to be
correlated with a considerable susceptibility to emotion. If I say
little about the emotions in this book, it is not from under-estimating
their human importance, but solely because the task upon which we are
engaged is theoretical rather than practical: to understand the world,
not to change it. And if emotion determines the ends we shall pursue,
knowledge is what gives us the power to realise them. Even from the
practical point of view, the advancement of knowledge is more useful
than anything else that lies within human power.

I come now to the subject of _desire_, which we considered from a
behaviourist standpoint in Chapter III. I want now to ask whether there
is anything to be added from an introspective point of view.

Let us again remind ourselves that there is an element of artificiality
in isolating elements within the one process leading from stimulus to
reaction. Whenever a stimulus produces a reaction, we may consider the
reaction as the effect of the stimulus, or as the cause of further
effects. The former is the natural way of viewing the reaction when we
are concerned with knowledge; the latter is the natural way when we are
concerned with desire and will. In desire, we wish to change something
in ourselves or in our environment or both. The question is: What can
we discover introspectively about desire?

I think that here, as in the case of knowledge, the purely
behaviouristic account is more important causally than the
introspective account, and applies over a much wider range. Desire as
a characteristic of behaviour, as considered in Chapter III, begins
very low in the scale of evolution, and remains, even in human beings,
the whole of what can be discovered in a large number of instances.
The Freudian “unconscious” desires give a formula which is useful as
explaining causally a number of acts, but these desires do not exist as
anything except ways of behaving. Some desires, on the other hand, are
conscious and explicit. What, exactly, is added in these last that is
not present in the others?

Let us take some stock instance, say, Demosthenes desiring to become
a great orator. This was a desire of which he was conscious, and
in accordance with which he deliberately moulded his actions. One
may suppose, to begin with, a merely behaviouristic tendency to do
such things as seemed likely to impress his companions. This is
a practically universal characteristic of human nature, which is
displayed naively by children. Then come attempts, just like those of
rats in mazes, to reach the goal; wrong turnings, leading to derision;
right turnings, leading to a brief nibble at the cheese of admiration.
Self-observation, still of a behaviourist kind, may lead to the
formula: I want to be admired. At this point the desire has become
“conscious”. When this point has been reached, knowledge can be brought
to bear on the problem of achieving the desired end. By association,
the means come to be desired also. And so Demosthenes arrives at the
decision to subject himself to a difficult training as an orator, since
this seems the best way of achieving his end. The whole development
is closely analogous to that of explicit knowledge out of mere
sensitivity; it is, indeed, part of the very same evolution. We cannot,
in our integral reaction to a situation, separate out one event as
knowledge and another as desire; both knowledge and desire are features
which characterise the reaction, but do not exist in isolation.

In explicit conscious desire there is always an object, just as there
is in explicit conscious perception; we desire some event or some state
of affairs. But in the primitive condition out of which explicit desire
is evolved, this is not the case. We have a state of affairs which may
be said to involve discomfort, and activities of various sorts until a
certain different state of affairs is achieved, or fatigue supervenes,
or some other interest causes a distraction. These activities will
be such as to achieve the new state of affairs quickly if there has
been previous experience of a relevant kind. When we reach the level
of explicit conscious desire, it seems as if we were being attracted
to a goal, but we are really still pushed from behind. The attraction
to the goal is a shorthand way of describing the effects of learning
together with the fact that our efforts will continue till the goal
is achieved, provided the time required is not too long. There are
feelings of various kinds connected with desire, and in the case of
familiar desires, such as hunger, these feelings become associated
with what we know will cause the desire to cease. But I see no more
reason in the case of desire than in the case of knowledge to admit
an _essentially_ relational occurrence such as many suppose desire to
be. Only experience, memory and association--so I should say--confer
objects upon desire, which are initially blind tendencies to certain
kinds of activity.

It remains to say a few words about “will”. There is a sense in
which will is an observable phenomena, and another in which it is a
metaphysical superstition. It is obvious that I can say, “I will hold
my breath for thirty seconds”, and proceed to do so; that I can say, “I
will go to America”, and proceed to do so; and so on. In this sense,
will is an observable phenomenon. But as a faculty, as a separable
occurrence, it is, I think, a delusion. To make this clear, it will be
necessary to examine the observable phenomenon.

Very young infants do not appear to have anything that could be called
“will”. Their movements, at first, are reflexes, and are explicable,
where they first cease to be reflexes, by the law of conditioned
reflexes. One observes, however, something that looks very like will
when the child learns control over fingers and toes. It seems clear,
in watching this process, that, after some experience of involuntary
movements, the child discovers how to think of a movement first
and then make the movement, and that this discovery is exceedingly
pleasurable. We know that, in adult life, a deliberate movement is one
which we think of before we make it. Obviously we cannot think of a
movement unless we have previously made it; it follows that no movement
can be voluntary unless it has previously been involuntary. I think
that, as William James suggested, a voluntary movement is merely one
which is preceded by the thought of it, and has the thought of it as an
essential part of its cause.

When I say this, I do not mean to take any particular view as to what
constitutes “thinking”. It may consist almost entirely of talking, as
Dr. Watson holds; or it may be something more. That is not the point
at present. The point is that, whatever philosophy one may adopt, there
certainly is an occurrence which is described by ordinary people as
“thinking of getting up in the morning”, or “thinking of” any other
bodily movement. Whatever the analysis of this occurrence may be, it is
an essential part of the cause of any movement which can be attributed
to the “will”.

It is true, of course, that we may think of a movement without
performing it. This is analogous to imagining a state of affairs
without believing in it; each is a rather sophisticated and late
development. Each will only happen when we think of several things
at once, and one of them interferes with another. It may, I think,
be assumed that, whenever we think of a possible movement, we have a
tendency to perform it, and are only restrained, if at all, by some
thought, or other circumstance, having a contrary tendency.

If this is the case, there is nothing at all mysterious about the will.
Whatever may constitute “thinking of” a movement, it is certainly
something associated with the movement itself; therefore, by the usual
law of learned reactions we should expect that thinking of a movement
would tend to cause it to occur. This, I should say, is the essence of
will.

Emphatic cases of volition, where we decide after a period of
deliberation, are merely examples of conflicting forces. You may have
both pleasant and unpleasant associations with some place that you are
thinking of going to; this may cause you to hesitate, until one or
other association proves the stronger. There may be more than this in
volition, but I cannot see any good ground for believing that there is.




CHAPTER XXII

ETHICS


Ethics is traditionally a department of philosophy, and that is my
reason for discussing it. I hardly think myself that it ought to be
included in the domain of philosophy, but to prove this would take as
long as to discuss the subject itself, and would be less interesting.

As a provisional definition, we may take ethics to consist of general
principles which help to determine rules of conduct. It is not the
business of ethics to say how a person should act in such and such
specific circumstances; that is the province of casuistry. The
word “casuistry” has acquired bad connotations, as a result of the
Protestant and Jansenist attacks on the Jesuits. But in its old and
proper sense it represents a perfectly legitimate study. Take, say,
the question: In what circumstances is it right to tell a lie? Some
people, unthinkingly, would say: Never! But this answer cannot be
seriously defended. Everybody admits that you should lie if you meet a
homicidal maniac pursuing a man with a view to murdering him, and he
asks you whether the man has passed your way. It is admitted that lying
is a legitimate branch of the art of warfare; also that priests may
lie to guard the secrets of the confessional, and doctors to protect
the professional confidences of their patients. All such questions
belong to casuistry in the old sense, and it is evident that they are
questions deserving to be asked and answered. But they do not belong to
ethics in the sense in which this study has been included in philosophy.

It is not the business of ethics to arrive at actual rules of conduct,
such as: “Thou shalt not steal”. This is the province of morals. Ethics
is expected to provide a basis from which such rules can be deduced.
The rules of morals differ according to the age, the race, and the
creed of the community concerned, to an extent that is hardly realised
by those who have neither travelled nor studied anthropology. Even
within a homogeneous community differences of opinion arise. Should a
man kill his wife’s lover? The Church says no, the law says no, and
common sense says no; yet many people would say yes, and juries often
refuse to condemn. These doubtful cases arise when a moral rule is
in process of changing. But ethics is concerned with something more
general than moral rules, and less subject to change. It is true that,
in a given community, an ethic which does not lead to the moral rules
accepted by that community is considered immoral. It does not, of
course, follow that such an ethic is in fact false, since the moral
rules of that community may be undesirable. Some tribes of head-hunters
hold that no man should marry until he can bring to the wedding the
head of an enemy slain by himself. Those who question this moral
rule are held to be encouraging licence and lowering the standard of
manliness. Nevertheless, we should not demand of an ethic that it
should justify the moral rules of head-hunters.

Perhaps the best way to approach the subject of ethics is to ask what
is meant when a person says: “You _ought_ to do so-and-so” or “I
_ought_ to do so-and-so”. Primarily, a sentence of this sort has an
emotional content; it means “this is the act towards which I feel the
emotion of approval”. But we do not wish to leave the matter there; we
want to find something more objective and systematic and constant than
a personal emotion. The ethical teacher says: “You ought to approve
acts of such-and-such kinds”. He generally gives reasons for this view,
and we have to examine what sorts of reasons are possible. We are here
on very ancient ground. Socrates was concerned mainly with ethics;
Plato and Aristotle both discussed the subject at length; before their
time, Confucius and Buddha had each founded a religion consisting
almost entirely of ethical teaching, though in the case of Buddhism
there was afterwards a growth of theological doctrine. The views of
the ancients on ethics are better worth studying than their views on
(say) physical science; the subject has not yet proved amenable to
exact reasoning, and we cannot boast that the moderns have as yet
rendered their predecessors obsolete.

Historically, virtue consisted at first of obedience to authority,
whether that of the gods, the government, or custom. Those who
disobeyed authority suffered obvious penalties. This is still the view
of Hegel, to whom virtue consists in obedience to the State. There
are, however, different forms of this theory, and the objections to
them are different. In its more primitive form, the theory is unaware
that different authorities take different views as to what constitutes
virtue, and it therefore universalises the practice of the community
in which the theoriser lives. When other ages and nations are found to
have different customs, these are condemned as abominations. Let us
consider this view first.

The view we are now to examine is the theory that there are certain
rules of conduct--_e.g._ the Decalogue--which determine virtue in all
situations. The person who keeps all the rules is perfectly virtuous;
the person who fails in this is wicked in proportion to the frequency
of his failures. There are several objections to this as the basis
of ethics. In the first place, the rules can hardly cover the whole
field of human conduct; _e.g._ there is nothing in the Decalogue to
show whether we ought to have a gold standard or not. Accordingly
those who hold this view regard some questions as “moral issues”,
while others have not this character. That means, in practice, that in
regard to “moral issues” we ought to act in a certain way, regardless
of consequences, while in other matters we ought to consider which
course will do the most good. Thus in effect we are driven to adopt two
different ethical systems, one where the code has spoken, the other
where it is silent. This is unsatisfactory to a philosopher.

The second objection to such a view is suggested by the first. We all
feel that certain results are desirable, and others undesirable; but
a code of conduct which takes no account of circumstances will have
sometimes the sort of consequences we think desirable, and sometimes
the sort we think undesirable. Take, _e.g._ the precept “Thou shalt
not kill”. All respectable people hold that this does not apply when
the State orders a person to kill; on this ground among others, the
New York School Board recently refused to sanction the teaching of the
Decalogue in schools.

A third objection is that it may be asked how the moral rules are
known. The usual answer, historically, is that they are known by
revelation and tradition. But these are extra-philosophical sources of
knowledge. The philosopher cannot but observe that there have been many
revelations, and that it is not clear why he should adopt one rather
than another. To this it may be replied that conscience is a personal
revelation to each individual, and invariably tells him what is right
and what is wrong. The difficulty of this view is that conscience
changes from age to age. Most people nowadays consider it wrong to burn
a man alive for disagreeing with them in metaphysics, but formerly this
was held to be a highly meritorious act, provided it was done in the
interests of the right metaphysics. No one who has studied the history
of moral ideas can regard conscience as invariably right. Thus we are
driven to abandon the attempt to define virtue by means of a set of
rules of conduct.

There is, however, another form of the view that virtue consists in
obedience to authority. This may be called “the administrator’s ethic”.
A Roman or Anglo-Indian pro-consul would define virtue as obedience to
the moral code of the community to which a man happens to belong. No
matter how moral codes may differ, a man should always obey that of
his own time and place and creed. A Mohammedan, for instance, would
not be regarded as wicked for practising polygamy, but an Englishman
would, even if he lived in a Mohammedan country. This view makes social
conformity the essence of virtue; or, as with Hegel, regards virtue as
obedience to the government. The difficulty of such theories is that
they make it impossible to apply ethical predicates to authority: we
cannot find any meaning for the statement that a custom is good or that
the government is bad. The view is appropriate to despots and their
willing slaves; it cannot survive in a progressive democracy.

We come a little nearer to a correct view when we define right conduct
by the motive or state of mind of the agent. According to this theory,
acts inspired by certain emotions are good, and those inspired by
certain other emotions are bad. Mystics hold this view, and have
accordingly a certain contempt for the letter of the law. Broadly
speaking, it would be held that acts inspired by love are good, and
those inspired by hate are bad. In practice, I hold this view to be
right; but philosophically I regard it as deducible from something more
fundamental.

All the theories we have hitherto considered are opposed to those which
judge the rightness or wrongness of conduct by its consequences. Of
these the most famous is the utilitarian philosophy, which maintained
that happiness is the good, and that we ought to act so as to maximise
the balance of happiness over unhappiness in the world. I should not
myself regard happiness as an adequate definition of the good, but I
should agree that conduct ought to be judged by its consequences. I do
not mean, of course, that in every practical exigency of daily life
we should attempt to think out the results of this or that line of
conduct, because, if we did, the opportunity for action would often
be past before our calculations were finished. But I do mean that
the received moral code, in so far as it is taught in education and
embodied in public opinion or the criminal law, should be carefully
examined in each generation, to see whether it still serves to achieve
desirable ends, and, if not, in what respects it needs to be amended.
The moral code, in short, like the legal code, should adapt itself to
changing circumstances, keeping the public good always as its motive.
If so, we have to consider in what the public good consists.

According to this view, “right conduct” is not an autonomous concept,
but means “conduct calculated to produce desirable results”. It will be
right, let us say, to act so as to make people happy and intelligent,
but wrong to act so as to make them unhappy and stupid. We have to
ask ourselves how we can discover what constitutes the ends of right
conduct.

There is a view, advocated, _e.g._ by Dr. G. E. Moore, that “good” is
an indefinable notion, and that we know _a priori_ certain general
propositions about the kinds of things that are good on their own
account. Such things as happiness, knowledge, appreciation of beauty,
are known to be good, according to Dr. Moore; it is also known that we
ought to act so as to create what is good and prevent what is bad. I
formerly held this view myself, but I was led to abandon it, partly by
Mr. Santayana’s _Winds of Doctrine_. I now think that good and bad are
derivative from desire. I do not mean quite simply that the good is the
desired, because men’s desires conflict, and “good” is, to my mind,
mainly a social concept, designed to find an issue from this conflict.
The conflict, however, is not only between the desires of different
men, but between incompatible desires of one man at different times,
or even at the same time, and even if he is solitary, like Robinson
Crusoe. Let us see how the concept of “good” emerges from reflection or
conflicts of desires.

We will begin with Robinson Crusoe. In him there will be conflicts,
for example, between fatigue and hunger, particularly between fatigue
at one time and foreseen hunger at another. The effort which he will
require in order to work when he is tired with a view to providing
food on another occasion has all the characteristics of what is called
a moral effort: we think better of a man who makes the effort than of
one who does not, and the making of it requires self-control. For some
reason, this sort of thing is called, not morals, but “morale”; the
distinction, however, seems to me illusory. Robinson Crusoe is bound
to realise that he has many desires, each of which is stronger at one
time than at another, and that, if he acts always upon the one that
is strongest at the moment, he may defeat others that are stronger in
the long run. So far, only intelligence is involved; but one may assume
that, with the progress of intelligence, there goes a growing desire
for a harmonious life, _i.e._ a life in which action is dominated by
consistent quasi-permanent desires. Again: some desires, in addition to
the desire for a harmonious life, are more likely to lead to harmony
then certain other desires. Intellectual curiosity, _e.g._ affords a
mild diffused satisfaction, whereas drugs provide ecstasy followed by
despair. If we arrive unexpectedly in Robinson Crusoe’s island and find
him studying botany, we shall think better of him than if we find him
dead drunk on his last bottle of whisky. All this belongs to morals,
although it is purely self-regarding.

When we come to considering men in society, moral questions become
both more important and more difficult, because conflicts between
the desires of different persons are harder to resolve than internal
conflicts among the desires of one person. There are some distinctions
to be made. First, there is the difference between the point of view
of the neutral authority contemplating a squabble in which it is not
interested, and the point of view of the disputants themselves. Then
there is the distinction between what we wish people to _do_, and what
we wish them to _feel_ in the way of emotions and desires.

The view of authority everywhere is that squabbles to which it is not a
party are undesirable, but that in the squabbles to which it is a party
virtue consists in promoting the victory of authority. In the latter
respect, it is acting, not as an authority, but merely as a combination
of quarrelsome individuals who think it more profitable to quarrel
with outsiders than with each other; we will therefore ignore this
aspect of authority, and consider its action only when it is a neutral.
In this case, it aims at preventing quarrels by punishing those who
begin them, or sometimes by punishing both parties. Monsieur Huc, the
Jesuit missionary who wrote a fascinating account of his travels in
China, Tartary, and Tibet about eighty years ago, relates an amusing
conversation he had with a mandarin. Monsieur Huc had remarked that
Chinese justice was dilatory, expensive, and corrupt. The mandarin
explained that it had been made so in obedience to an Imperial edict,
setting forth that the subjects of the Son of Heaven had become too
much addicted to litigation, and must be led to abandon this practice.
The rescript then proceeded to suggest to magistrates and judges
the desirability of the above defects as a means of diminishing the
number of law-suits. It appeared that the Emperor’s commands had been
faithfully obeyed in this respect--more so than in some others.

Another method adopted by public authorities to prevent the impulse
towards internal quarrels is the creation of _esprit de corps_, public
spirit, patriotism, etc., _i.e._ a concentration of quarrelsome
impulses or persons outside the group over which it rules. Such a
method, obviously, is partial and external; it would not be open to a
world-wide democratic authority, should this ever come into existence.
Such an authority would have to adopt better methods of producing
harmony; it would also have a higher claim to the obedience of citizens
than some authorities have at present.

What can we say from the point of view of the disputants themselves? It
is of course obvious that there will be a greater _total_ satisfaction
when two people’s desires harmonise than when they conflict, but that
is not an argument which can be used to people who in fact hate each
other. One can argue that the one who is going to be beaten would do
well to give way, but each will think that he himself is going to be
victorious. One can argue that there is more happiness to be derived
from love than from hate, but people cannot love to order, and there is
no satisfaction to be derived from an insincere love. Nor is it always
true in an individual case that love brings more happiness than hate.
During and immediately after the war, those who hated the Germans were
happier than those who still regarded them as human beings, because
they could feel that what was being done served a good purpose. I
think, therefore, that certain departments of morals, and those the
most important, cannot be inculcated from a personal point of view, but
only from the point of view of a neutral authority. That is why I said
that ethics is mainly social.

The attitude of a neutral authority would, it seems to me, be this:
Men desire all sorts of things, and in themselves all desires,
taken singly, are on a level, _i.e._ there is no reason to prefer
the satisfaction of one to the satisfaction of another. But when we
consider not a single desire but a group of desires, there is this
difference, that sometimes all the desires in a group can be satisfied,
whereas in other cases the satisfaction of some of the desires in
the group is incompatible with that of others. If A and B desire to
marry each other, both can have what they want, but if they desire to
kill each other, at most one can succeed, unless they are Kilkenny
cats. Therefore the former pair of desires is socially preferable to
the latter. Now our desires are a product of three factors: native
disposition, education, and present circumstances. The first factor is
difficult to deal with at present, for lack of knowledge. The third is
brought into operation by means of the criminal law, economic motives,
and social praise and blame, which make it on the whole to the interest
of an individual in a community to promote the interests of the
dominant group in that community. But this is done in an external way,
not by creating good desires, but by producing a conflict of greed and
fear in which it is hoped that fear will win. The really vital method
is education, in the large sense in which it includes care of the body
and habit-formation in the first few years. By means of education,
men’s desires can be changed, so that they act spontaneously in a
social fashion. To force a man to curb his desires, as we do by the
criminal law, is not nearly so satisfactory as to cause him genuinely
to feel the desires which promote socially harmonious conduct.

And this brings me to the last point with which we are concerned,
namely, the distinction between feeling and doing. No doubt, from a
social point of view the important thing is what a man does, but it is
impossible to cause a man to do the right things consistently unless he
has the right desires. And the right desires cannot be produced merely
by praising them or by desiring to have them; the technique of moral
education is not one of exhortation or _explicit_ moral instruction.

We can now state the ethic at which we have arrived in abstract terms.
Primarily, we call something “good” when we desire it, and “bad” when
we have an aversion from it. But our use of words is more constant than
our desires, and therefore we shall continue to call a thing good even
at moments when we are not actually desiring it, just as we always
call grass green though it sometimes looks yellow. And the laudatory
associations of the word “good” may generate a desire which would not
otherwise exist: we may want to eat caviare merely because we are told
that it is good. Moreover the use of words is social, and therefore
we learn only to call a thing good, except in rare circumstances, if
most of the people we associate with are also willing to call it good.
Thus “good” comes to apply to things desired by the whole of a social
group. It is evident, therefore, that there can be more good in a world
where the desires of different individuals harmonise than in one where
they conflict. The supreme moral rule should, therefore, be: _Act so
as to produce harmonious rather than discordant desires_. This rule
will apply wherever a man’s influence extends: within himself, in his
family, his city, his country, even the world as a whole, if he is able
to influence it.

There will be two main methods to this end: first, to produce social
institutions under which the interests of different individuals or
groups conflict as little as possible; second, to educate individuals
in such a way that their desires can be harmonised with each other and
with the desires of their neighbours. As to the first method, I shall
say nothing further, since the questions that arise belong to politics
and economics. As to the second, the important period is the formative
period of childhood, during which there should be health, happiness,
freedom, and a gradual growth of self-discipline through opportunities
for difficult achievement of a sort which is useful and yet satisfies
the impulse towards mastery of the environment. The desire for power,
which is present in most people and strongest in the most vigorous,
should be directed towards power over things rather than over people.

It is clear that, if harmonious desires are what we should seek, love
is better than hate, since, when two people love each other, both
can be satisfied, whereas when they hate each other one at most can
achieve the object of his desire. It is obvious also that desire for
knowledge is to be encouraged, since the knowledge that a man acquires
is not obtained by taking it away from some one else; but a desire for
(say) large landed estates can only be satisfied in a small minority.
Desire for power over other people is a potent source of conflict,
and is therefore to be discouraged; a respect for the liberty of
others is one of the things that ought to be developed by the right
kind of education. The impulse towards personal achievement ought to
go into such things as artistic creation or scientific discovery or
the promotion of useful institutions--in a word, into activities that
are creative rather than possessive. Knowledge, which may do positive
harm where men’s desires conflict (for example, by showing how to make
war more deadly), will have only good results in a world where men’s
desires harmonise, since it tends to show how their common desires are
to be realised.

The conclusion may be summed up in a single phrase: _The good life is
one inspired by love and guided by knowledge_.[11]

     [11] Cf. _What I Believe_, by the present author--To-day and
          To-morrow Series.




PART IV

THE UNIVERSE




CHAPTER XXIII

SOME GREAT PHILOSOPHIES OF THE PAST


Our discussions, hitherto, have been concerned very largely with
Man, but Man on his own account is not the true subject-matter of
philosophy. What concerns philosophy is the universe as a whole; Man
demands consideration solely as the instrument by means of which we
acquire knowledge of the universe. And that is why it is human beings
as capable of knowledge that have concerned us mainly in past chapters,
rather than as centres of will or of emotion. We are not in the mood
proper to philosophy so long as we are interested in the world only as
it affects human beings; the philosophic spirit demands an interest in
the world for its own sake. But since we apprehend the world through
our own senses, and think about it with our own intellect, the picture
that we acquire is inevitably coloured by the personal medium through
which it comes to us. Consequently we have to study this medium,
namely ourselves, in order to find out, if we can, what elements in
our picture of the world are contributed by us, and what elements we
may accept as representative of outside fact. Previous chapters have
studied cognition, both as an outwardly observable reaction, and as
it appears to introspection. In the chapters that remain, we shall
be concerned with what we can know about the universe, in view of
the nature of the instrument that we have to employ. I do not think
we can know as much as many philosophers of the past have supposed,
but I think it is worth while to have in our minds an outline of
their systems. I shall therefore begin by setting forth a few typical
philosophical constructions of earlier centuries.

Modern philosophy is generally taken as beginning with Descartes,
who flourished in the first half of the seventeenth century. We have
already had occasion, in Chapter XVI, to consider his argument “I
think, therefore, I am”, but now we will deal with him somewhat more
generally. He inaugurated two movements, one in metaphysics, one in
theory of knowledge. In metaphysics, he emphasised the gulf between
mind and matter, or between soul and body; in theory of knowledge he
advocated a critical scrutiny of premises. These two movements had
different histories, each of them interesting. The science of dynamics
was rapidly developing in Descartes’ time, and seemed to show that the
motions of matter could be calculated mathematically, given sufficient
data. As the motions of matter include our bodily acts, even speaking
and writing, it seemed as if the consequence must be a materialistic
theory of human behaviour. This consequence, however, was distasteful
to most philosophers, and they therefore invented various ways of
escaping from it. Descartes himself thought that the will could have
certain direct physical effects. He thought that the brain contains a
fluid called the “animal spirits”, and that the will could influence
the direction of its motion, though not the velocity. In this way he
was still able to hold that the will is effective in the manner in
which common sense supposes it to be. But this view did not fit in at
all well with the rest of his philosophy. He held that, apart from the
Supreme Substance, namely God, there are two created substances, mind
and matter; that the essence of mind is thought, and that the essence
of matter is extension. He made these two substances so different
that interaction between them became difficult to understand, and his
followers decided that there is never any effect either of mind on
matter or of matter on mind.

The motives for this development were various; perhaps the most
important was the development of physics immediately after Descartes’
time. A law was discovered called the “conservation of momentum”. This
states that, if a system of bodies is in any sort of motion, and is
free from outside influences, the amount of motion _in any direction_
is constant. This showed that the kind of action of the will on the
“animal spirits” which Descartes had assumed was contrary to the
principles of dynamics. It seemed to follow that mind cannot influence
matter, and it was inferred that matter cannot influence mind, since
the two were regarded as co-equal substances. It was held that each
goes it own way, according to its own laws. The fact that our arm moves
when we will it to move was regarded as analogous to the fact that two
perfectly accurate clocks strike at the same moment, though neither
has any effect upon the other. The series of mental events and the
series of physical events were parallel, each going at the same rate as
the other, therefore they continued to synchronise, in spite of their
independence of each other.

Spinoza sought to make this parallelism less mysterious by denying
that there are two separate substances, mind and matter. He maintained
that there is only one substance, of which thought and extension are
attributes. But there seemed still no good reason why the events
belonging to the two attributes should develop along parallel lines.
Spinoza is in many ways one of the greatest philosophers, but his
greatness is rather ethical than metaphysical. Accordingly he was
regarded by contemporaries as a profound metaphysician but a very
wicked man.

The notion of the impossibility of interaction between mind and body
has persisted down to our own day. One still hears of “psychophysical
parallelism”, according to which to every state of the brain a state of
mind _corresponds_ and vice versa, without either acting on the other.
This whole point of view, though not exactly that of Descartes, derives
from him. It has a number of sources, religious, metaphysical, and
scientific; but there seems no ground whatever for regarding it as true.

Take, first, the rigid determinism of traditional physics, which was
to have been avoided. Spinoza rightly perceived that this could not
be avoided by such methods, and therefore accepted determinism in
the psychical as in the physical realm. If everything we _say_ is
determined by physical causes, our thoughts are only free when we
tell lies: so long as we say what we think, our thoughts also can be
inferred from physics. The philosophy which I advocate escapes this
consequence in several ways. In the first place, causality does not
involve _compulsion_, but only a law of sequence: if physical and
mental events run parallel, either may with equal justice be regarded
as causing the other, and there is no sense in speaking of them as
causally independent. Thus the Cartesian dualism does not have the
pleasant consequences which were intended. In the second place, modern
physics has become less deterministic than the physics of the past
few centuries. We do not know, _e.g._ what makes a radio-active atom
explode or an electron jump from a larger to a smaller orbit. In these
matters we only know statistical averages.

Take next the view that mind and matter are quite disparate. This we
have criticised already. It rests upon a notion that we know much
more about matter than we do, and in particular upon the belief that
the space of physics can be identified with the space of sensible
experience. This belief is absent in Leibniz, who, however, never quite
realised what his own view was. It is not absent in Kant, who realised
that the space of sensible experience is subjective, and inferred
that the space of physics is subjective. Since Kant, no one seems to
have thought clearly about space until Einstein and Minkowski. The
separation of physical and sensible space, logically carried out, shows
the groundlessness of traditional views about mind and matter. This
part of Descartes’ philosophy, therefore, though it accelerated the
progress of physics, must be regarded as metaphysically an aberration.

The other part of Descartes’ philosophy, namely, the emphasis upon
methodical doubt, and consequently upon theory of knowledge, has
been more fruitful. The beginning of a philosophic attitude is the
realisation that we do not know as much as we think we do, and to this
Descartes contributed notably. We have seen that he set to work to
doubt all he could, but found he could not doubt his own existence,
which he therefore took as the starting-point of his constructive
system. He supposed that the most certain fact in the world is “I
think”. This was unfortunate, since it gave a subjective bias to modern
philosophy. As a matter of fact, “I” seems to be only a string of
events, each of which separately is more certain than the whole. And
“think” is a word which Descartes accepted as indefinable, but which
really covers complicated relations between events. When is an event
a “thought”? Is there some intrinsic characteristic which makes it a
thought? Descartes would say yes, and so would most philosophers. I
should say no. Take, _e.g._ a visual and an auditory sensation. Both
are “thoughts” in Descartes’ sense, but what have they in common? Two
visual sensations _have_ an indefinable common quality, viz. that
which makes them visual. Two auditory sensations likewise. But a
visual and an auditory sensation have in common, if I am not mistaken,
no intrinsic property, but a certain capacity for being _known_
without inference. This amounts to saying that they are mnemic causes
of a certain kind of event, called a cognition, and that they have
moreover, a certain formal similarity to the cognition which they
cause. Therefore, instead of taking the general “I think” as our basis,
we ought to take the particular occurrences which are known without
inference, among which sensations (or rather “perceptions”) will be
included. These occurrences, as we have already seen, may be regarded
with equal justice as physical and mental: they are parts of chains of
physical causation, and they have mnemic effects which are cognitions.
The former fact makes us call them physical, the latter mental, both
quite truly. It is the particular events which are certain, not the
“I think” which Descartes made the basis of his philosophy. It is not
correct to regard the ultimate certainties as “subjective”, except in
the sense that they are events in that part of space-time in which our
body is--and our mind also, I should say.

A new turn was given to the Cartesian type of metaphysics by Leibniz
(1646–1716), who, like Descartes, was supremely eminent both in
mathematics and in philosophy. Leibniz rejected the view that there
is only one substance, as Spinoza held, or only two other than God,
as the orthodox followers of Descartes maintained. He also rejected
the dualism of mind and matter, holding that there are innumerable
substances all in a greater or less degree mental, and none in any
degree material. He maintained that every substance is immortal, and
that there is no interaction between one substance and another--this
last being a view derived from the Cartesian independence of mind
and matter. He also extended to his many substances the belief in
parallelism which had existed for the two substances of the Cartesians.
He called his substances “monads”, and maintained that every monad
mirrors the universe, and develops along lines which correspond, point
by point, with those along which every other monad is developing. A
man’s soul or mind is a single monad, while his body is a collection of
monads, each mental in some degree, but less so than the monad which
is his soul. Inferior monads mirror the world in a more confused way
than higher ones do, but there is some element of confusion in the
perceptions of even the most superior monads. Every monad mirrors the
world from its own point of view, and the difference between points of
view is compared to a difference of perspective. “Matter” is a confused
way of perceiving a number of monads; if we perceived clearly, we
should see that there is no such thing as matter.

Leibniz’s system had great merits and great demerits. The theory that
“matter” is a confused way of perceiving something non-material was
an advance upon anything to be found in his predecessors. He had,
though only semi-consciously, the distinction between physical and
perceptual space: there is space in each monad’s picture of the world,
and there is also the assemblage or pattern of “points of view”. The
latter corresponds to what I have called “physical space”, the former
to “perceptual space”. Leibniz maintained, as against Newton, that
space and time consists only of relations--a view which has achieved a
definitive triumph in Einstein’s theory of relativity. The weak point
of his system was what he called the “pre-established harmony”, in
virtue of which all the monads (so to speak) kept step, in spite of
the fact that they were “windowless” and never acted upon each other.
Perception, for Leibniz, was not an effect of the object perceived, but
a modification arising in the perceiving monad and running parallel
with what was happening in the perceived object. This view would
never have seemed plausible but for the anterior Cartesian theory of
the mutual independence of mind and matter. And if Leibniz himself
developed, as he believed, in complete independence of all other
created things, it is not clear what good reasons he could have had for
believing in the existence of anything except himself, since, by his
own theory, his experiences would remain unchanged if everything else
were annihilated. In fact, he was only able to refute this possibility
by bringing in theological considerations, which, whether valid or
not, are out of place in philosophy. For this reason, his doctrines,
ingenious as they were, found little acceptance in France and England,
though in Germany they prevailed, in a modified form, until the time of
Kant.

The systems of Descartes, Spinoza and Leibniz have one very important
characteristic in common, namely, that they all depend upon the
category of “substance”. This is a concept which has developed out of
the common-sense notion of “thing”. A “substance” is that which has
qualities, and is in general supposed to be indestructible, though
it is difficult to see why. It acquired its hold over metaphysicians
partly because both matter and the soul were held to be immortal, and
partly through a hasty transference to reality of ideas derived from
grammar. We say “Peter is running”, “Peter is talking”, “Peter is
eating”, and so on. We think that there is one entity, Peter, who does
all these things, and that none of them could be done unless there were
someone to do them, but that Peter might quite well do none of them.
Similarly we assign qualities to Peter: we say he is wise and tall
and blond and so on. All these qualities, we feel, cannot subsist by
themselves in the void, but only when there is a subject to which they
belong; but Peter would remain Peter even if he became foolish and
short and dyed his hair. Thus Peter, who is regarded as a “substance”,
is self-subsistent as compared with his qualities and states, and he
preserves his substantial identity throughout all sorts of changes.
Similarly in the material world an atom is supposed (or rather was
supposed until recently) to preserve its identity throughout all time,
however it might move and whatever combinations it might form with
other atoms. The concept of “motion”, upon which all physics seemed to
depend, was only strictly applicable to a substance which preserves
its identity while changing its spatial relations to other substances;
thus “substance” acquired an even firmer hold upon physics than upon
metaphysics.

Nevertheless, the notion of “substance”, at any rate in any sense
involving permanence, must be shut out from our thoughts if we are to
achieve a philosophy in any way adequate either to modern physics or
to modern psychology. Modern physics, both in the theory of relativity
and in the Heisenberg-Schrödinger theories of atomic structure, has
reduced “matter” to a system of events, each of which lasts only for a
very short time. To treat an electron or a proton as a single entity
has become as wrong-headed as it would be to treat the population of
London or New York as a single entity. And in psychology, equally,
the “ego” has disappeared as an ultimate conception, and the unity
of a personality has become a peculiar causal nexus among a series
of events. In this respect, grammar and ordinary language have been
shown to be bad guides to metaphysics. A great book might be written
showing the influence of syntax on philosophy; in such a book, the
author could trace in detail the influence of the subject-predicate
structure of sentences upon European thought, more particularly in
this matter of “substance”. And it must be understood that the same
reasons which lead to the rejection of substance lead also to the
rejection of “things” and “persons” as ultimately valid concepts. I
say “I sit at my table”, but I ought to say: “One of a certain string
of events causally connected in the sort of way that makes the whole
series that is called a ‘person’ has a certain spatial relation to one
of another string of events causally connected with each other in a
different way and having a spatial configuration of the sort denoted
by the word ‘table’”. I do not say so, because life is too short; but
that is what I should say if I were a true philosopher. Apart from
any other grounds, the inadequacy of the notion of “substance” would
lead us to regard the philosophy of Descartes, Spinoza, and Leibniz as
incompatible with modern science. There is of course in all three, a
great deal that does not depend upon “substance”, and that still has
value; but “substance” supplied the framework and a good deal of the
argumentation, and therefore introduces a fatal defect into these three
great systems.

I come now to the triad of British philosophers, Locke, Berkeley, and
Hume--English, Irish, and Scotch respectively. Perhaps from patriotic
bias or from community of national temperament, I find more that I
can accept, and regard as still important, in the writings of these
three than in the philosophy of their continental predecessors. Their
constructions are less ambitious, their arguments more detailed, and
their methods more empirical; in all these respects they show more
kinship with the modern scientific outlook. On the other hand, Locke
and Hume, if not Berkeley, approach philosophy too exclusively from
the side of psychology, and are concerned to study Man rather than the
universe.

Locke was a contemporary and friend of Newton; his great book, _An
Essay concerning Human Understanding_, was published at almost the
same moment as Newton’s _Principia_. His influence has been enormous,
greater, in fact, than his abilities would seem to warrant; and this
influence was not only philosophical, but quite as much political and
social. He was one of the creators of eighteenth century liberalism:
democracy, religious toleration, freedom of economic enterprise,
educational progress, all owe much to him. The English Revolution of
1688 embodied his ideas; the American Revolution of 1776 and the
French Revolution of 1789 expressed what had grown, in a century, out
of his teaching. And in all these movements, philosophy and politics
went hand in hand. Thus the practical success of Locke’s ideas has been
extraordinary.

When, knowing all this, one comes to read Locke himself, it is
difficult to resist a feeling of disappointment. He is sensible,
enlightened, minute, but uninspired and (to moderns) uninspiring.
One has to remember that his contemporaries found common sense
exhilarating after a century of wars of religion and a long struggle
with obscurantism. Locke combatted the doctrine of “innate ideas”,
according to which we learned only certain things by experience,
but possessed our abstract knowledge in virtue of our congenital
constitution. He regarded the mind at birth as a wax tablet, upon which
experience proceeded to write. Undoubtedly he was, in this matter,
more in the right than his opponents, although the terms in which the
controversy was waged are not such as a modern could employ. We should
say that the innate apparatus of man consists of “reflexes” rather than
“ideas”; also that our sense-organs, our glands, and our muscles lead
to responses of certain kinds, in which our own organisation plays a
part of the same importance as that played by the external stimulus.
The element in our knowledge-responses that corresponds to our own
bodily organisation might, perhaps, be regarded as representing what
Locke’s opponents meant by “innate”. But it does not represent this
at all accurately so far as our feelings towards it are concerned.
The “innate” ideas were the ideas to be proud of; they embraced pure
mathematics, natural theology, and ethics. But nobody is proud of
sneezing or coughing. And when Locke tried to show, in detail, how our
knowledge is generated by experience, he was liberating philosophy from
a great deal of useless lumber, even if his own doctrines were not
altogether such as we can now accept.

Locke used his own principles only in ways consistent with common
sense; Berkeley and Hume both pushed them to paradoxical conclusions.
The philosophy of Berkeley, to my mind, has not received quite the
attention and respect that it deserves--not that I agree with it,
but that I think it ingenious and harder to refute than is often
supposed. Berkeley, as everyone knows, denied the reality of matter,
and maintained that everything is mental. In the former respect I
agree with him, though not for his reasons; in the latter respect, I
think his argument unsound and his conclusion improbable, though not
certainly false. However, I will leave the development of my own views
to a later chapter, and confine myself to Berkeley’s argument.

Berkeley contended that when, for example, you “see a tree”, all
that you really _know_ to be happening is in you, and is mental. The
colour that you see, as Locke had already argued, does not belong to
the physical world, but is an effect upon you, produced, according
to Locke, by a physical stimulus. Locke held that the purely spatial
properties of perceived objects really belong to the objects, whereas
such things as colour, softness, sound, etc., are effects in us.
Berkeley went further, and argued that the spatial properties of
perceived objects are no exception. Thus the object perceived is
composed entirely of “mental” constituents, and there is no reason to
believe in the existence of anything not mental. He did not wish to
admit that a tree ceases to exist when we do not look at it, so he
maintained that it acquires permanence through being an idea in the
mind of God. It is still only an “idea”, but not one whose existence
depends upon the accidents of our perceptions.

The real objection to Berkeley’s view is rather physical than
metaphysical. Light and sound take time to travel from their sources
to the percipient, and one must suppose that something is happening
along the route by which they travel. What is happening along the route
is presumably not “mental”, for, as we have seen, “mental” events are
those that have peculiar mnemic effects which are connected with living
tissue. Therefore, although Berkeley is right in saying that the events
we know immediately are mental, it is highly probable that he is wrong
as to the events which we infer in places where there are no living
bodies. In saying this, however, we are anticipating the results of a
fuller discussion in a later chapter.

Hume, proceeding from a starting-point essentially similar to that
of Locke and Berkeley, arrived at conclusions so sceptical that all
subsequent philosophers have shied away from them. He denied the
existence of the Self, questioned the validity of induction, and
doubted whether causal laws could be applied to anything except our own
mental processes. He is one of the very few philosophers not concerned
to establish any positive conclusions. To a great extent, I think, we
must admit the validity of his reasons for refusing to feel the usual
certainties. As regards the Self, he was almost certainly right. As we
have already argued, a person is not a single entity, but a series of
events linked together by peculiar causal laws. As regards induction,
the question is very difficult, and I shall devote a subsequent chapter
to it. As regards causal laws, the question, as we shall find later, is
the same as the question of induction. On both points Hume’s doubts are
not to be lightly dismissed.

The usual modern criticism of Locke, Berkeley, and Hume is that they
were unduly “atomistic”. They thought of the mind as a collection of
“ideas”, each as hard and separate as a billiard-ball. They had not
the conception of continuous change or of integral processes; their
causal units were too small. As we have already seen in connection with
_Gestaltpsychologie_ and with sentences, the causal unit is often a
configuration which cannot be broken up without losing its distinctive
causal properties. In this sense, it is true that the traditional
British philosophy was too atomistic. But in another sense I do not
think it is true, and I think much modern philosophy is confused on
this point. Although a configuration may lose its _causal_ properties
when broken up into its elements, it nevertheless does consist of
these elements related in certain ways; analysis into “atoms” is
perfectly valid, so long as it is not assumed that the causal efficacy
of the whole is compounded out of the separate effects of the separate
atoms. It is because I hold this view that I call the philosophy which
I advocate “logical atomism”. And to this extent I regard Locke,
Berkeley, and Hume as in the right as against their modern critics. But
this also is a topic which will be resumed in a later chapter.

Hume’s criticism of the notion of cause was what led Kant to his new
departure. Kant’s philosophy is difficult and obscure, and philosophers
still dispute as to what he meant. Those who disagree with him are held
by his supporters to have misunderstood him; I must therefore warn the
reader that what follows is my view of what he meant, and that there is
no agreed view.

Kant maintained that, in virtue of our mental constitution, we deal
with the raw material of sense-impressions by means of certain
“categories” and by arranging it in space and time. Both the categories
and the space-time arrangement are supplied by us, and do not belong to
the world except as known by us. But since our mental constitution is
a constant datum, all phenomena _as known_ will be spatio-temporal and
will conform to the categories. Among the latter “cause” is the most
important. Thus although there may be no cause in the world as it is
in itself (a point on which Kant was inconsistent in the interest of
morals), yet phenomena, _i.e._ things as they seem to us, will always
have other phenomena as their causes. And although there is no time in
the real world, things as they appear to us will be some earlier and
some later. Space, again is supplied by us, and therefore geometry can
be known _a priori_, without our having to study the outer world. Kant
thought that Euclidean geometry was quite certainly true, although it
could not be proved by logic alone, since Euclid’s axioms could be
denied without self-contradiction.

It was on this question of geometry that the weakness of Kant’s
system first became obvious. It was found that we have no grounds for
regarding Euclidean geometry as quite true. Since Einstein, we have
positive grounds for regarding it as not quite true. It appears that
geometry is just as empirical as geography. We depend upon observation
if we want to know whether the sum of the angles of a triangle is two
right angles just as much as if we want to know how much land there is
in the western hemisphere.

With regard to the “categories” there are equally great difficulties.
Let us take “cause” as our illustration. We see lightning, and then we
hear thunder; as phenomena, our seeing and hearing are connected as
cause and effect. But we must not--if we are to take the subjectivity
of “cause” seriously--suppose that our seeing or our hearing has an
outside cause. In that case, we have no reason to suppose that there
is anything outside ourselves. Nay, more: what _really_ happens when
we see is not, according to Kant, what we perceive by introspection;
what really happens is something without a date, without a position
in space, without causes and without effects. Thus we do not know
ourselves any better than we know the outside world. Space and time
and the categories interpose a mirage of illusion which cannot be
penetrated at any point. As an answer to Hume’s scepticism, this
seems a somewhat unsuccessful effort. And Kant himself, later, in the
_Critique of Practical Reason_, demolished much of his own edifice,
because he thought that ethics at least must have validity in the
“real” world. This part of his philosophy, however, is usually ignored
by his followers or apologetically minimised.

Kant gave a new turn to an old philosophical controversy, as to how
far our knowledge is _a priori_ and how far it is based on experience.
Kant admitted that without experience we could know nothing, and that
what we know is only valid within the realm of experience. But he held
that the general framework of our knowledge is _a priori_ in the sense
that it is not proved by means of particular facts of experience, but
represents the conditions to which phenomena have to conform in order
to be capable of being experienced. Before his day, the tendency had
been for continental philosophers to regard almost everything as
_a priori_ while British philosophers regarded almost everything as
empirical. But both sides thought that what is _a priori_ can be proved
by logic, at least in theory, whereas Kant held that mathematics is
_a priori_ and yet “synthetic”, _i.e._ not capable of being proved
by logic. In this he was misled by geometry. Euclidean geometry,
considered as true, is “synthetic” but not _a priori_; considered
merely as deducing consequences from premisses, it is _a priori_
but not “synthetic”. The geometry of the actual world, as required
by engineers, is empirical; the geometry of pure mathematics, which
does not inquire into the truth of the axioms but merely shows their
implications, is an exercise in pure logic.

It should be said, however, that, if the correct analysis of knowledge
bears any resemblance at all to that which has been suggested in this
book, the whole controversy between empiricists and apriorists becomes
more or less unreal. All beliefs are _caused_ by external stimuli; when
they are as particular as the stimuli they are of the sort which an
empiricist might regard as _proved_ by experience, but when they are
more general difficulties arise. A foreigner arrives in America and
sees the immigration officials, who lead him to the generalisation that
all Americans are rude; but a few minutes later the porter upsets this
induction in the hope of a tip. Thus sometimes a given belief will be
caused by one event and destroyed by another. If all the events in a
man’s life, so far as they affect the belief in question, are such as
to cause it, he counts the belief true. The more general a belief is,
the more events are relevant to it, and therefore the more difficult
it is for it to be such as a man will long consider true. Roughly
speaking, the beliefs which count as _a priori_ will be those which
well might have been upset by subsequent events, but in fact were
confirmed. Here as elsewhere we are driven to the view that theory of
knowledge is not so fundamental as it has been considered since Kant.

There is one more traditional controversy which I wish to consider,
namely, that between monists and pluralists. Is the universe one,
or is it many? If many, how intimately are they interconnected? The
monistic view is very old: it is already complete in Parmenides (fifth
century B.C.). It is fully developed in Spinoza, Hegel, and Bradley.
The pluralistic view, on the other hand, is found in Heraclitus,
the atomists, Leibniz, and the British empiricists. For the sake of
definiteness, let us take the monistic view as found in Bradley, who
is in the main a follower of Hegel. He maintains that every judgment
consists in assigning a predicate to Reality as a whole: the whole is
the subject of every predicate. Suppose you start by saying “Tommy
has a cold in the head”. This may not _seem_ to be a statement about
the universe as a whole, but according to Bradley it is. If I may
be allowed to set forth his argument in popular language which his
followers might resent, I should put it something like this: First of
all, who is Tommy? He is a person with a certain nature, distinguished
from other persons by that nature; he may resemble others in many
respects, but not in all, so that you cannot really explain who Tommy
is unless you set forth all his characteristics. But when you try to
do this, you are taken beyond Tommy: he is characterised by relations
to his environment. He is affectionate or rebellious or thirsty, noisy
or quiet, and so on; all of these qualities involve his relations
to others. If you try to define Tommy without mentioning anything
outside him, you will find this quite impossible; therefore he is not a
self-subsistent being, but an unsubstantial fragment of the world. The
same thing applies even more obviously to his nose and his cold. How do
you know he has a cold? Because material substances of a certain kind
pass from his nose to his handkerchief, which would not be possible
if he alone existed. But now, when you take in the environment with a
view to defining Tommy and his nose and his cold, you find that you
cannot define his immediate environment without taking account of its
environment, and so on, until at last you have been forced to include
the whole world. Therefore Tommy’s cold is in reality a property of
the world, since nothing short of the world is sufficiently substantial
to have properties.

We may put the argument in a more abstract form. Everything which is
part of the world is constituted, in part, by its relations to other
things; but relations cannot be real. Bradley’s argument against
relations is as follows. First he argues that, if there are relations,
there must be qualities between which they hold. This part of the
argument need not detain us. He then proceeds:

“But how the relation can stand to the qualities is, on the other
side, unintelligible. If it is nothing to the qualities, then they
are not related at all; and, if so, as we saw, they have ceased to
be qualities, and their relation is a nonentity. But if it is to be
something to them, then clearly we shall require a _new_-connecting
relation. For the relation hardly can be the mere adjective of one or
both of its terms; or, at least, as such it seems indefensible. And,
being something itself, if it does not itself bear a relation to the
terms, in what intelligible way will it succeed in being anything to
them? But here again we are hurried off into the eddy of a hopeless
process, since we are forced to go on finding new relations without
end. The links are united by a link, and this bond of union is a link
which also has two ends; and these require each a fresh link to connect
them with the old. The problem is to find how the relation can stand to
its qualities, and this problem is insoluble.”

I cannot deal adequately with this argument without abstruse
technicalities which would be out of place. I will, however, point out
what seems to me the essential error. Bradley conceives a relation as
something just as substantial as its terms, and not radically different
in kind. The analogy of the chain with links should make us suspicious,
since it clearly proves, if it is valid, that chains are impossible,
and yet, as a fact, they exist. There is not a word in his argument
which would not apply to physical chains. The successive links are
united not by another link, but by a spatial relation. I think Bradley
has been misled, unconsciously, by a circumstance to which I alluded
in an earlier chapter, namely, the fact that the _word_ for a relation
is as substantial as the _words_ for its terms. Suppose A and B are
two events, and A precedes B. In the proposition “A precedes B”, the
word “precedes” is just as substantial as the words “A” and “B”. The
relation of the _two_ events A and B is represented, in language, by
the time or space order of the _three_ words “A”, “precedes”, and
“B”. But this order is an actual relation, not a word for relation.
The first step in Bradley’s regress does actually have to be taken in
giving verbal expression to a relation, and the word for a relation
does have to be related to the words for its terms. But this is a
linguistic, not a metaphysical, fact, and the regress does not have to
go any further.

It should be added that, as Bradley himself recognises, his
difficulties break out afresh when he comes to consider the relation of
subject and predicate when a character is assigned to Reality, and that
he is therefore compelled to conclude that _no_ truth is quite true.
A conclusion of this sort, based upon an extremely abstract argument,
makes it natural to suspect that there is some error in the argument.

Pluralism is the view of science and common sense, and is therefore
to be accepted if the arguments against it are not conclusive. For
my part, I have no doubt whatever that it is the true view, and that
monism is derived from a faulty logic inspired by mysticism. This logic
dominates the philosophy of Hegel and his followers; it is also the
essential basis of Bergson’s system, although it is seldom mentioned in
his writings. When it is rejected, ambitious metaphysical systems such
as those of the past are seen to be impossible.




CHAPTER XXIV

TRUTH AND FALSEHOOD


The question of truth and falsehood has been wrapped in unnecessary
mystery owing to a number of causes. In the first place, people wish to
think that their beliefs are more apt to be true than false, so that
they seek a theory that will show that truth is normal and falsehood
more or less accidental. In the second place, people are very vague as
to what they mean by “belief” or “judgment”, though persuaded that they
know beliefs or judgments to be the objects to which the predicates
“true” or “false” apply. In the third place, there is a tendency to
use “truth” with a big T in the grand sense, as something noble and
splendid and worthy of adoration. This gets people into a frame of mind
in which they become unable to think. But just as the grave-diggers in
_Hamlet_ became familiar with skulls, so logicians become familiar with
truth. “The hand of little employment hath the daintier sense,” says
Hamlet. Therefore it is not from the logician that awe before truth is
to be expected.

There are two questions in our present subject: (1) What are the
objects to which the predicates “true” and “false” apply? (2) What is
the difference between such as are true and such as are false? We will
begin with the first of these questions.

_Prima facie_, “true” and “false” apply to statements, whether in
speech or in writing. By extension, they are supposed to apply to the
beliefs expressed in those statements, and also to hypotheses which are
entertained without being believed or disbelieved. But let us first
consider the truth and falsehood of statements, following our practice
of going as far as we can with the behaviourists before falling back on
introspection. We considered the meaning of words earlier; now we have
to consider sentences. Of course a sentence may consist of a single
word, or of a wink; but generally it consists of several words. In
that case, it has a meaning which is a function of the meanings of the
separate words and their order. A sentence which has no meaning is not
true or false; thus it is only sentences as vehicles of a certain sort
of meaning that have truth or falsehood. We have therefore to examine
the meaning of a sentence.

Let us take some very humble example. Suppose you look in a time-table
and find it there stated that a passenger train leaves King’s Cross for
Edinburgh at 10 A.M. What is the meaning of this assertion? I shudder
when I think of its complexity. If I were to try to develop the theme
adequately, I should be occupied with nothing else till the end of
the present volume, and then I should have only touched the fringe of
the subject. Take first the social aspect: it is not essential that
anybody but the engineer and fireman should travel by the train, though
it is essential that others should be _able_ to travel by it if they
fulfil certain conditions. It is not essential that the train should
reach Edinburgh: the statement remains true if there is an accident or
breakdown on the way. But it is essential that the management of the
railway should intend it to reach Edinburgh. Take next the physical
aspect: it is not essential, or even possible, that the train should
start _exactly_ at ten; one might perhaps say that it must not start
more than ten seconds before its time or more than fifty seconds after,
but these limits cannot be laid down rigidly. In countries where
unpunctuality is common they would be much wider. Then we must consider
what we mean by “starting”, which no one can define unless he has
learnt the infinitesimal calculus. Then we consider the definitions of
King’s Cross and Edinburgh, both of which are more or less vague terms.
Then we must consider what is meant by a “train”. Here there will be
first of all complicated legal questions; what constitutes fulfilment
of a railway company’s obligations in the way of running “trains”? Then
there are questions as to the constitution of matter, since evidently
a train is a piece of matter; also of course there are questions as
to methods of estimating Greenwich time at King’s Cross. Most of the
above points have to do with the meaning of single words, not with the
meaning of the whole sentence. It is obvious that the ordinary mortal
does not trouble about such complications when he uses the words: to
him a word has a meaning very far from precise, and he does not try to
exclude marginal cases. It is the search for precision that introduces
complications. We think we attach a meaning to the word “man”, but we
don’t know whether to include Pithecanthropus Erectus. To this extent,
the meaning of the word is vague.

As knowledge increases, words acquire meanings which are more precise
and more complex; new words have to be introduced to express the less
complex constituents which have been discovered. A word is intended to
describe something in the world; at first it does so very badly, but
afterwards it gradually improves. Thus single words embody knowledge,
although they do not make assertions.

In an ideal logical language, there will be words of different kinds.
First, proper names. Of these, however, there are no examples in
actual language. The words which are _called_ proper names describe
collections, which are always defined by some characteristic;
thus assertions about “Peter” are really about everything that is
“Peterish”. To get a true proper name, we should have to get to a
single particular or a set of particulars defined by enumeration,
not by a common quality. Since we cannot acquire knowledge of actual
particulars, the words we use denote, in the best language we can make,
either adjectives or relations between two or more terms. In addition
to these, there are words indicative of structure: _e.g._ in “A is
greater than B”, the words “is” and “than” have no separate meaning,
but merely serve to show the “sense” of the relation “greater”, _i.e._
that it goes from A to B, not from B to A.

Strictly speaking, we are still simplifying. True adjectives and
relations will require particulars for their terms; the sort of
adjectives we can know, such as “blue” and “round”, will not be
applicable to particulars. They are therefore analogous to the
adjective “populous” applied to a town. To say “this town is populous”
means “many people live in this town”. A similar transformation would
be demanded by logic in all the adjectives and relations we can know
empirically. That is to say, no word that we can understand would occur
in a grammatically correct account of the universe.

Leaving on one side the vagueness and inaccuracy of words, let us ask
ourselves; in what circumstances do we feel convinced that we know a
statement to be true or false as the case may be? A present statement
will be regarded as true if, _e.g._ it agrees with recollection or
perception; a past statement, if it raised expectations now confirmed.
I do not mean to say that these are the only grounds upon which we
regard statements as true; I mean that they are simple and typical,
and worth examining. If you say “it was raining this morning”, I may
recollect that it was or that it wasn’t. One may perhaps say that the
words “this morning” are associated for me with the word “raining” or
with the words “not raining”. According to which occurs, I judge your
statement true or false. If I have neither association, I do not judge
your statement either true or false unless I have material for an
inference; and I do not wish to consider inference yet. If you say “the
lights have gone out”, when I can see the lights shining, I judge that
you speak falsely, because my perception is associated with the words
“lights shining”. If you say “the lights will go out in a minute”, you
produce a certain familiar kind of tension called “expectation”, and
after a time you produce a judgment that you spoke falsely (if the
lights do not go out). These are the ordinary _direct_ ways of deciding
on the truth or falsehood of statements about past, present, or future.

It is necessary to distinguish between direct and indirect grounds
for accepting or rejecting statements. Pragmatism considers only
indirect grounds. Broadly speaking, it considers a statement false when
the consequences of accepting it are unfortunate. But this belongs
to the region of inference. I ask you the way to the station, you
tell me wrong, and I miss my train; I then _infer_ that you told me
wrong. But if you say “the lights are out” when I see them shining,
I reject your statement without inference. In this case, something
in my present circumstances is associated with words different from
yours, and different in ways which I have learnt to regard as involving
incompatibility. The ultimate test of falsehood is _never_, so I think,
the nature of the consequences of a belief, but the association between
words and sensible or remembered facts. A belief is “verified” when a
situation arises which gives a feeling of expectedness in connection
with it; it is falsified when the feeling is one of surprise. But
this only applies to beliefs which await some future contingency for
verification or refutation. A belief which is an immediate reaction
to a situation--_e.g._ when you are waiting for a race to begin and
presently you say “they’re off”--has no need of verification, but
verifies other beliefs. And even where the confirmation of a belief is
in the future, it is the expectedness, not the pleasantness, of the
consequences that confirms the truth of the belief.

I think it is a mistake to treat “belief” as one kind of occurrence,
as is done in traditional psychology. The sort of belief which is
based upon memory or perception alone differs from the sort which
involves expectation. When you find in the time-table that a train
leaves King’s Cross at ten, your belief that this statement occurs in
the time-table does not await future confirmation, but your belief
about the train does: you may go to King’s Cross and see the train
start. A belief which concerns an event may be a recollection, a
perception, or an expectation. It may be none of these, in the case of
an event which you have not seen and do not expect to see--_e.g._ Cæsar
crossing the Rubicon, or the abolition of the House of Lords. But
such beliefs always involve inference. I do not at this stage consider
logical and mathematical beliefs, some of which must be, _in a sense_,
non-inferential. But I think we shall find that this sense is different
from that in which memories and perceptions are non-inferential.

A belief, I should say, interpreted narrowly, is a form of words
related to an emotion of one of several kinds. (I shall give a broader
meaning later.) The emotion is different according as the belief
embodies a reminiscence, a perception, an expectation, or something
outside the experience of the believer. Moreover, a form of words
is not essential. Where the emotion is present, and leads to action
relevant to some feature of the environment, there may be said to be
a belief. The fundamental test of a belief, of no matter what sort,
is that it causes some event which actually takes place to arouse
the emotion of expectedness or its opposite. I do not now attempt to
decide what an emotion is. Dr. Watson gives a behaviouristic account
of emotions, which would, if adopted, make my definition of “belief”
purely behaviouristic. I have framed the definition so as not to
involve a decision on the question of introspection.

The subject of truth and falsehood may be subdivided as follows:

  A. _Formal Theory._--Given the meanings of the component words, what
      decides whether a sentence is true or false?

  B. _Causal Theory._--Can we distinguish between truth and falsehood
      by (_a_) their causes, (_b_) their effects?

  C. _Individual and Social Elements._--A statement is a social
      occurrence, a belief is something individual.

      How can we define a belief, and what is it when not composed of
      words?

  D. _Consistency and Truth._--Can we get outside the circle of
      beliefs or statements to something else which shows them true,
      not merely consistent? In other words, what possible relation is
      there between propositions and facts?

It is very hard to disentangle these questions. The first question,
as to formal theories, leads to the fourth, as to the relations of
propositions to facts. _E.g._ “Brutus killed Cæsar” is true because
of a certain fact; what fact? The fact that Brutus killed Cæsar. This
keeps us in the verbal realm, and does not get us outside it to some
realm of non-verbal fact by which verbal statements can be verified.
Hence our fourth problem arises. But this leads us to our second
problem, as to causes and effects of what is true or false, for it
is here that we shall naturally look for the vital relation between
propositions and facts. And here again we must distinguish between
_thinking_ truly and _speaking_ truly. The former is an individual
affair, the latter a social affair. Thus all our problems hang together.

I will begin with C, the difference between a belief and a statement.
By a “statement” I mean a form of words, uttered or written, with a
view to being heard or read by some other person or persons, and not
a question, interjection, or command, but such as we should call an
assertion. As to the question what forms of words are assertions, that
is one for the grammarian and differs from language to language. But
perhaps we can say rather more than that. The distinction, however,
between an assertion and an imperative is not sharp. In England,
notices say “Visitors are requested not to walk on the grass”. In
America, they say “Keep off! This means you.” Effectively, the two have
the same meaning: yet the English notice consists only of a statement,
while the American notice consists of an imperative followed by a
statement which must be false if read by more than one person. In so
far as statements are intended to influence the conduct of others, they
partake of the nature of imperatives or requests. Their characteristic,
however, is that they endeavour to effect their aim by producing a
_belief_ which may or may not exist in the mind of the speaker. Often,
however, they _express_ a belief, without stopping to consider the
effect upon others. Thus a statement may be defined as a form of words
which either expresses a belief or is intended to create one. Our next
step, therefore, must be the definition of “belief”.

“Belief” is a word which will be quite differently defined if we take
an analytic point of view from the way in which we shall define it if
we regard the matter causally. From the point of view of science, the
causal point of view is the more important. Beliefs influence action
in certain ways; what influences action in these ways may be called a
belief, even if, analytically, it does not much resemble what would
ordinarily be so called. We may therefore widen our previous definition
of belief. Consider a man who goes to the house where his friend used
to live, and, finding he has moved, says, “I _thought_ he still lived
here”, whereas he acted merely from habit without thought. If we are
going to use words causally, we ought to say that this man had a
“belief” and therefore a “belief” will be merely a characteristic of
a string of actions. We shall have to say: A man “believes” a certain
proposition _p_ if, whenever he is aiming at any result to which _p_
is relevant, he acts in a manner calculated to achieve the result if
_p_ is true, but not otherwise. Sometimes this gives definite results,
sometimes not. When you call a telephone number, it is clear that you
believe that to be the number of the subscriber you want. But whether
you believe in the conservation of energy or a future life may be
harder to decide. You may hold a belief in some contexts and not in
others; for we do not think in accordance with the so-called “Laws
of Thought”. “Belief” like all the other categories of traditional
psychology, is a notion incapable of precision.

This brings me to the question whether the truth or falsehood of a
belief can be determined either by its causes or by its effects. There
is, however, a preliminary difficulty. I said just now that A believes
_p_ if he acts in a way which will achieve his ends if _p_ is _true_.
I therefore assumed that we know what is meant by “truth”. I assumed,
to be definite, that we know what is meant by “truth” as applied to
a form of words. The argument was as follows: From observation of
a person’s acts, you infer his beliefs, by a process which may be
elaborate as the discovery of Kepler’s Laws from the observed motions
of the planets. His “beliefs” are not assumed to be “states of mind”,
but merely characteristics of series of actions. These beliefs, when
ascertained by observation, can be expressed in words; you can say,
_e.g._ “This person believes that there is a train from King’s Cross at
10 A.M.” Having once expressed the belief in words of which the meaning
is known, you have arrived at the stage where formal theories are
applicable. Words of known meaning, put together according to a known
syntax, are true or false in virtue of some fact, and their relation to
this fact results logically from the meanings of the separate words and
the laws of syntax. This is where logic is strong.

It will be seen that, according to what we have said, truth is
applicable primarily to a form of words, and only derivatively to
a belief. A form of words is a social phenomenon, therefore the
fundamental form of truth must be social. A form of words is true when
it has a certain relation to a certain fact. What relation to what
fact? I think the fundamental relation is this: a form of words is true
if a person who knows the language is led to that form of words when
he finds himself in an environment which contains features that are
the meanings of those words, and these features produce reactions in
him sufficiently strong for him to use words which mean them. Thus “a
train leaves King’s Cross at 10 A.M.” is true if a person can be led
to say, “It is now 10 A.M., this is King’s Cross, and I see a train
starting”. The environment causes words, and words directly caused by
the environment (if they are statements) are “true”. What is called
“verification” in science consists in putting oneself in a situation
where words previously used for other reasons result directly from
the environment. Of course, given this basis, there are innumerable
indirect ways of verifying statements, but all, I think, depend upon
this direct way.

The above theory may be thought very odd, but it is partly designed
to meet the fourth of our previous questions, namely, “How can we get
outside words to the facts which make them true or false?” Obviously we
cannot do this within logic, which is imprisoned in the realm of words;
we can only do it by considering the relations of words to our other
experiences, and these relations, in so far as they are relevant, can
hardly be other than causal. I think the above theory, as it stands,
is too crude to be quite true. We must also bring in such things as
expectedness, which we discussed earlier. But I believe that the
definition of truth or falsehood will have to be sought along some such
lines as I have indicated.

I want in conclusion to indulge in two speculations. The first concerns
a possible reconciliation of behaviourism and logic. It is clear that,
when we have a problem to solve, we do not always solve it as the rat
does, by means of random movements; we often solve it by “thinking”,
_i.e._ by a process in which we are not making any overt movements.
The same thing was sometimes true of Köhler’s chimpanzees. Now what is
involved in the possibility of solving a problem by verbal thinking?
We put words together in various ways which are not wholly random, but
limited by previous knowledge of the _sort_ of phrase that is likely to
contain a solution of our problem. At last we hit upon a phrase which
seems to give what we want. We then proceed to an overt action of the
kind indicated by the phrase; if it succeeds, our problem is solved.
Now this process is only intelligible if there is some connection
between the laws of syntax and the laws of physics--using “syntax”
in a psychological rather than a grammatical sense. I think this
connection is _assumed_ in logic and ordinary philosophy, but it ought
to be treated as a problem requiring investigation by behaviourist
methods. I lay no stress on this suggestion, except as giving a hint
for future investigations. But I cannot think that the behaviourist has
gone far towards the solution of his problem until he has succeeded in
establishing a connection between syntax and physics. Without this,
the efficacy of “thought” cannot be explained on his principles.

My second speculation is as to the limitations which the structure
of language imposes upon the extent of our possible knowledge of
the world. I am inclined to think that quite important metaphysical
conclusions, of a more or less sceptical kind, can be drawn from simple
considerations as to the relation between language and things. A spoken
sentence consists of a temporal series of events; a written sentence
is a spatial series of bits of matter. Thus it is not surprising that
language can represent the course of events in the physical world;
it can, in fact, make a map of the physical world, preserving its
structure in a more manageable form, and it can do this because it
consists of physical events. But if there were such a world as the
mystic postulates, it would have a structure different from that of
language, and would therefore be incapable of being verbally described.
It is fairly clear that nothing verbal can conform or confute this
hypothesis.

A great deal of the confusion about relations which has prevailed in
practically all philosophies comes from the fact that relations are
indicated, not by relations, but by words which are as substantial as
other words. Consequently, in thinking about relations, we constantly
hover between the unsubstantiality of the relation itself and the
substantiality of the word. Take, say, the fact that lightning precedes
thunder. We saw earlier that to express this by a language closely
reproducing the structure of the fact, we should have to say simply:
“lightning, thunder”, where the fact that the first word precedes the
second means that what the first word means precedes what the second
word means. But even if we adopted this method for temporal order, we
should still need words for all other relations, because we could not
without intolerable ambiguity symbolise them also by the order of our
words. When we say “lightning precedes thunder”, the word “precedes”
has a quite different relation to what it means from that which the
words “lightning” and “thunder” have to what they respectively mean.
Wittgenstein[12] says that what really happens is that we establish a
relation between the word “lightning” and the word “thunder”, namely
the relation of having the word “precedes” between them. In this way he
causes relations to be symbolised by relations. But although this may
be quite correct, it is sufficiently odd to make it not surprising that
people have thought the word “precedes” means a relation in the same
sense in which “lightning” means a kind of event. This view, however,
must be incorrect. I think it has usually been held unconsciously, and
has produced many confusions about relations which cease when it is
exposed to the light of day--for example, those which lead Bradley to
condemn relations.

     [12] _Tractatus Logico-Philosophicus_ (Kegan Paul).

In all this I have been considering the question of the relation
between the structure of language and the structure of the world. It is
clear that anything that can be said in an inflected language can be
said in an uninflected language; therefore, everything that can be said
in language can be said by means of a temporal series of uninflected
words. This places a limitation upon what can be expressed in words.
It may well be that there are facts which do not lend themselves to
this very simple schema; if so, they cannot be expressed in language.
Our confidence in language is due to the fact that it consists of
events in the physical world, and, therefore, shares the structure of
the physical world, and therefore can express that structure. But if
there be a world which is not physical, or not in space-time, it may
have a structure which we can never hope to express or to know. These
considerations might lead us to something like the Kantian _a priori_,
not as derived from the structure of the mind, but as derived from the
structure of language, which is the structure of the physical world.
Perhaps that is why we know so much physics and so little of anything
else. However, I have lapsed into mystical speculation, and will leave
these possibilities, since, by the nature of the case, I cannot _say_
anything true about them.




CHAPTER XXV

THE VALIDITY OF INFERENCE


It is customary in science to regard certain facts as “data”, from
which laws and also other facts are “inferred”. We saw in Chapter VII
that the _practice_ of inference is much wider than the theories of any
logician would justify, and that it is nothing other than the law of
association or of “learned reactions”. In the present chapter, I wish
to consider what the logicians have evolved from this primitive form of
inference, and what grounds we have, as rational beings, for continuing
to infer. But let us first get as clear a notion as we can of what
should be meant by a “datum”.

The conception of a “datum” cannot be made absolute. Theoretically,
it should mean something that we know without inference. But before
this has any definite meaning, we must define both “knowledge” and
“inference”. Both these terms have been considered in earlier chapters.
For our present purpose it will simplify matters to take account only
of such knowledge as is expressed in words. We considered in Chapter
XXIV the conditions required in order that a form of words may be
“true”; for present purposes, therefore, we may say that “knowledge”
means “the assertion of a true form of words”. This definition is not
quite adequate, since a man may be right by chance; but we may ignore
this complication. We may then define a “datum” as follows: A “datum”
is a form of words which a man utters as the result of a stimulus, with
no intermediary of any learned reaction beyond what is involved in
knowing how to speak. We must, however, permit such learned reactions
as consist in adjustments of the sense-organs or in mere increase of
sensitivity. These merely improve the receptivity to data, and do not
involve anything that can be called inference.

If the above definition is accepted, all our data for knowledge of
the external world must be of the nature of percepts. The belief in
external objects is a learned reaction acquired in the first months of
life, and it is the duty of the philosopher to treat it as an inference
whose validity must be tested. A very little consideration shows that,
logically, the inference cannot be demonstrative, but must be at best
probable. It is not logically _impossible_ that my life may be one
long dream, in which I merely imagine all the objects that I believe
to be external to me. If we are to reject this view, we must do so on
the basis of an inductive or analogical argument, which cannot give
complete certainty. We perceive other people behaving in a manner
analogous to that in which we behave, and we assume that they have had
similar stimuli. We may hear a whole crowd say “oh” at the moment when
we see a rocket burst, and it is natural to suppose that the crowd
saw it too. Nor are such arguments confined to living organisms. We
can talk to a dictaphone and have it afterwards repeat what we said;
this is most easily explained by the hypothesis that at the surface
of the dictaphone events happened, while I was speaking, which were
closely analogous to those that were happening just outside my ears.
It remains _possible_ that there is no dictaphone and I have no ears
and there is no crowd watching the rocket; my percepts _may_ be all
that is happening in such cases. But, if so, it is difficult to arrive
at any causal laws, and arguments from analogy are more misleading
than we are inclined to think them. As a matter of fact, the whole
structure of science, as well as the world of common sense, demands
the use of induction and analogy if it is to be believed. These forms
of inference, therefore, rather than deduction, are those that must be
examined if we are to accept the world of science or any world outside
of our own dreams.

Let us take a simple example of an induction which we have all
performed in practice. If we are hungry, we eat certain things we see
and not others--it may be said that we infer edibility inductively
from a certain visual and olfactory appearance. The history of this
process is that children a few months old put everything into their
mouths unless they are stopped; sometimes the result is pleasant,
sometimes unpleasant; they repeat the former rather than the latter.
That is to say: given that an object having a certain visual and
olfactory appearance has been found pleasant to eat, an object having
a very similar appearance will be eaten; but when a certain appearance
has been found connected with unpleasant consequences when eaten, a
similar appearance does not lead to eating next time. The question is:
what logical justification is there for our behaviour? Given all our
past experience, are we more likely to be nourished by bread than by a
stone? It is easy to see why we think so, but can we, as philosophers
justify this way of thinking?

It is, of course, obvious that unless one thing can be a sign of
another both science and daily life would be impossible. More
particularly, reading involves this principle. One accepts printed
words as signs, but this is only justifiable by means of induction.
I do not mean that induction is necessary to establish the existence
of other people, though that also, as we have seen, is true. I mean
something simpler. Suppose you want your hair cut, and as you walk
along the street you see a notice “hair-cutting, first floor”. It
is only by means of induction that you can _establish_ that this
_notice_ makes it in some degree probable that there is a hair-cutter’s
establishment on the first floor. I do not mean that you employ the
principle of induction; I mean that you act in accordance with it,
and that you would have to appeal to it if you were accompanied by a
long-haired sceptical philosopher who refused to go upstairs till he
was persuaded there was some point in doing so.

The principle of induction, _prima facie_, is as follows: Let there
be two kinds of events, A and B (_e.g._ lightning and thunder), and
let many instances be known in which an event of the kind A has
been quickly followed by one of the kind B, and no instances of the
contrary. Then either a sufficient number of instances of this
sequence, or instances of suitable kinds will make it increasingly
probable that A is always followed by B, and in time the probability
can be made to approach certainty without limit provided the right
kind and number of instances can be found. This is the principle we
have to examine. Scientific theories of induction generally try to
substitute well-chosen instances for numerous instances, and represent
number of instances as belonging to crude popular induction. But in
fact popular induction depends upon the emotional interest of the
instances, not upon their number. A child who has burnt its hand
_once_ in a candle-flame establishes an induction, but words take
longer, because at first they are not emotionally interesting. The
principle used in primitive practice is: Whatever, on a given occasion,
immediately precedes something very painful or pleasant, is a sign
of that interesting event. Number plays a secondary part as compared
with emotional interest. That is one reason why rational thought is so
difficult.

The logical problem of induction is to show that the proposition “A
is always accompanied (or followed) by B” can be rendered probable by
knowledge of instances in which this happens, provided the instances
are suitably chosen or very numerous. Far the best examination of
induction is contained in Mr. J. M. Keynes’s _Treatise on Probability_.
There is a valuable doctor’s thesis by the late Jean Nicod, _Le
Problème logique de l’induction_, which is very ably reviewed by R. B.
Braithwaite in _Mind_, October 1925. A man who reads these three will
know most of what is known about induction. The subject is technical
and difficult, involving a good deal of mathematics, but I will attempt
to give the gist of the results.

We will begin with the condition in which the problem had been left by
J. S. Mill. He had four canons of induction, by means of which, given
suitable examples, it could be demonstrated that A and B were causally
connected, if the law of causation could be assumed. That is to say,
given the law of causation, the scientific use of induction could
be reduced to deduction. Roughly the method is this: We know that B
must have a cause; the cause cannot be C or D or E, etc., because we
find by experiment or observation that these may be present without
producing B. On the other hand, we never succeed in finding A without
its being accompanied (or followed) by B. If A and B are both capable
of quantity, we may find further that the more there is of A the more
there is of B. By such methods we eliminate all possible causes except
A; therefore, since B must have a cause, that cause must be A. All
this is not really induction at all; true induction only comes in in
proving the law of causation. This law Mill regards as proved by mere
enumeration of instances: we know vast numbers of events which have
causes, and no events which can be shown to be uncaused; therefore, it
is highly probable that all events have causes. Leaving out of account
the fact that the law of causality cannot have quite the form that Mill
supposed, we are left with the problem: Does mere number of instances
afford a basis for induction? If not, is there any other basis? This is
the problem to which Mr. Keynes addresses himself.

Mr. Keynes holds that an induction may be rendered more probable by
number of instances, not because of their mere number, but because of
the probability, if the instances are very numerous, that they will
have nothing in common except the characteristics in question. We want,
let us suppose, to find out whether some quality A is always associated
with some quality B. We find instances in which this is the case; but
it may happen that in all our instances some quality C is also present,
and that it is C that is associated with B. If we can so choose our
instances that they have nothing in common except the qualities A and
B, then we have better grounds for holding that A is always associated
with B. If our instances are very numerous, then, even if we do not
_know_ that they have no other common quality, it may become quite
likely that this is the case. This, according to Mr. Keynes, is the
sole value of many instances.

A few technical terms are useful. Suppose we want to establish
inductively that there is some probability in favour of the
generalisation: “Everything that has the property _F_ also has the
property _f_”. We will call this generalisation _g_. Suppose we have
observed a number of instances in which _F_ and _f_ go together, and
no instances to the contrary. These instances may have other common
properties as well; the sum-total of their common properties is called
the _total positive analogy_, and the sum-total of their _known_ common
qualities is called the _known positive analogy_. The properties
belonging to some but not to all of the instances in question are
called the _negative analogy_: all of them constitute the _total
negative analogy_, all those that are _known_ constitute the _known
negative analogy_. To strengthen an induction, we want to diminish the
positive analogy to the utmost possible extent; this, according to Mr.
Keynes, is why numerous instances are useful.

On “pure” induction, where we rely solely upon number of instances,
without _knowing_ how they affect the analogy, Mr. Keynes concludes
(_Treatise in Probability_, p. 236):

“We have shown that if each of the instances necessarily follows
from the generalisation, then each additional instance increases the
probability of the generalisation, so long as the new instance could
not have been predicted with certainty from a knowledge of the former
instances.... The common notion, that each successive verification of
a doubtful principle strengthens it, is formally proved, therefore
without any appeal to conceptions of law or of causality. _But we have
not proved_ that this probability approaches certainty as a limit, or
even that our conclusion becomes more likely than not, as the number of
verifications or instances is indefinitely increased.”

It is obvious that induction is not much use unless, with suitable
care, its conclusions can be rendered more likely to be true than
false. This problem therefore necessarily occupies Mr. Keynes.

It is found that an induction will approach certainty as a limit if two
conditions are fulfilled:

(1) If the generalisation is false, the probability of its being true
in a new instance when it has been found to be true in a certain
number of instances, however great that number may be, falls short of
certainty by a finite amount.

(2) There is a finite _a priori_ probability in favour of our
generalisation.

Mr. Keynes uses “finite” here in a special sense. He holds that not all
probabilities are numerically measurable; a “finite” probability is one
which exceeds some numerically measurable probability however small.
_E.g._ our generalisation has a finite _a priori_ probability if it is
less unlikely than throwing heads a billion times running.

The difficulty is, however, that there is no easily discoverable way of
estimating the _a priori_ probability of a generalisation. In examining
this question, Mr. Keynes is led to a very interesting postulate
which, if true, will, he thinks, give the required finite _a priori_
probability. His postulate as he gives it is not quite correct, but I
shall give his form first, and then the necessary modification.

Mr. Keynes supposes that the qualities of objects cohere in groups,
so that the number of _independent_ qualities is much less than the
total number of qualities. We may conceive this after the analogy
of biological species: a cat has a number of distinctive qualities
which are found in all cats, a dog has a number of other distinctive
qualities which are found in all dogs. The method of induction can, he
says, be justified if we assume “that the objects in the field, over
which our generalisations extend, do not have an infinite number of
independent qualities; that, in other words, their characteristics,
however numerous, cohere together in groups of invariable connection,
which are finite in number” (p. 256). Again (p. 258): “As a biological
foundation for Analogy, therefore, we seem to need some such assumption
as that the amount of variety in the universe is limited in such a way
that there is no one object so complex that its qualities fall into an
infinite number of independent groups ... or rather that none of the
objects about which we generalise are as complex as this; or at least
that, though some objects may be infinitely complex, we sometimes have
a finite probability that an object about which we seek to generalise
is not infinitely complex.”

This postulate is called the “principle of limitation of variety”. Mr.
Keynes again finds that it is needed in attempts to establish laws
by statistics; if he is right, it is needed for all our scientific
knowledge outside pure mathematics. Jean Nicod pointed out that it is
not quite sufficiently stringent. We need, according to Mr. Keynes,
a finite probability that the object in question has only a finite
number of independent qualities; but what we really need is a finite
probability that the number of its independent qualities is less than
some assigned finite number. This is a very different thing, as may be
seen by the following illustration. Suppose there is some number of
which we know only that it is finite; it is infinitely improbable that
it will be less than a million, or a billion, or any other assigned
finite number, because, whatever such number we take, the number
of smaller numbers is finite and the number of greater numbers is
infinite. Nicod requires us to assume that there is a finite number _n_
such that there is a finite probability that the number of independent
qualities of our object is less than _n_. This is a much stronger
assumption than Mr. Keynes’s, which is merely that the number of
independent qualities is finite. It is the stronger assumption which is
needed to justify induction.

This result is very interesting and very important. It is remarkable
that it is in line with the trend of modern science. Eddington has
pointed out that there is a certain finite number which is fundamental
in the universe, namely the number of electrons. According to the
quantum theory, it would seem that the number of possible arrangements
of electrons may well also be finite, since they cannot move in all
possible orbits, but only in such as make the action in one complete
revolution conform to the quantum principle. If all this is true, the
principle of limitation of variety may well also be true. We cannot,
however, arrive at a proof of our principle in this way, because
physics uses induction, and is therefore presumably invalid unless
the principle is true. What we can say, in a general way, is that
the principle does not refute itself, but, on the contrary, leads to
results which confirm it. To this extent, the trend of modern science
may be regarded as increasing the plausibility of the principle.

It is important to realise the fundamental position of probability in
science. At the very best, induction and analogy only give probability.
Every inference worthy of the name is inductive, therefore all inferred
knowledge is at best probable. As to what is meant by probability,
opinions differ. Mr. Keynes takes it as a fundamental logical category:
certain premisses may make a conclusion more or less probable, without
making it certain. For him, probability is a relation between a premiss
and a conclusion. A proposition does not have a definite probability
on its own account; in itself, it is merely true or false. But it has
probabilities of different amounts in regard to different premisses.
When we speak, elliptically, of _the_ probability of a proposition,
we mean its probability in relation to all our relevant knowledge.
A proposition in probability cannot be refuted by mere observation:
improbable things may happen and probable things may fail to happen.
Nor is an estimate of probability relevant to given evidence proved
wrong when further evidence alters the probability.

For this reason the inductive principle cannot be proved or disproved
by experience. We might prove validly that such and such a conclusion
was enormously probable, and yet it might not happen. We might
prove invalidly that it was probable, and yet it might happen.
What happens affects the probability of a proposition, since it is
relevant evidence; but it never alters the probability relative to
the previously available evidence. The whole subject of probability,
therefore, on Mr. Keynes’s theory, is strictly _a priori_ and
independent of experience.

There is however another theory, called the “frequency theory”, which
would make probability not indefinable, and would allow empirical
evidence to affect our estimates of probability relative to given
premisses. According to this theory in its crude form, the probability
that an object having the property _F_ will have the property _f_ is
simply the proportion of the objects having both properties to all
those having the property _F_. For example, in a monogamous country
the probability of a married person being male is exactly a half. Mr.
Keynes advances strong arguments against all forms of this theory that
existed when his book was written. There is however an article by R. H.
Nisbet on “The Foundations of Probability” in _Mind_ for January 1926,
which undertakes to rehabilitate the frequency theory. His arguments
are interesting, and suffice to show that the controversy is still an
open one, but they do not, in my opinion, amount to decisive proof.
It is to be observed, however, that the frequency theory, if it could
be maintained, would be preferable to Mr. Keynes’s, because it would
get rid of the necessity for treating probability as indefinable, and
would bring probability into much closer touch with what actually
occurs. Mr. Keynes leaves an uncomfortable gap between probability and
fact, so that it is far from clear why a rational man will act upon a
probability. Nevertheless, the difficulties of the frequency theory
are so considerable that I cannot venture to advocate it definitely.
Meanwhile, the details of the discussion are unaffected by the view
we may take on this fundamental philosophical question. And on either
view the principle of limitation of variety will be equally necessary
to give validity to the inferences by induction and analogy upon which
science and daily life depend.




CHAPTER XXVI

EVENTS, MATTER, AND MIND


Everything in the world is composed of “events”; that, at least, is the
thesis I wish to maintain. An “event”, as I understand it, is something
having a small finite duration and a small finite extension in space;
or rather, in view of the theory of relativity, it is something
occupying a small finite amount of space-time. If it has parts, these
parts, I say, are again events, never something occupying a mere point
of instant, whether in space, in time, or in space-time. The fact that
an event occupies a finite amount of space-time does not prove that it
has parts. Events are not impenetrable, as matter is supposed to be; on
the contrary, every event in space-time is overlapped by other events.
There is no reason to suppose that any of the events with which we are
familiar are infinitely complex; on the contrary, everything known
about the world is compatible with the view that every complex event
has a finite number of parts. We do not know that this is the case,
but it is an hypothesis which cannot be refuted and is simpler than
any other possible hypothesis. I shall therefore adopt it as a working
hypothesis in what follows.

When I speak of an “event” I do not mean anything out of the way.
Seeing a flash of lightning is an event; so is hearing a tire burst,
or smelling a rotten egg, or feeling the coldness of a frog. These
are events that are “data” in the sense of Chapter XXV; but, on the
principles explained in that chapter, we infer that there are events
which are not data and happen at a distance from our own body. Some of
these are data to other people, others are data to no one. In the case
of the flash of lightning, there is an electro-magnetic disturbance
consisting of events travelling outward from the place where the flash
takes place, and then when this disturbance reaches the eye of a
person or animal that can see, there is a percept, which is causally
continuous with the events between the place of the lightning and the
body of the percipient. Percepts afford the logical premisses for all
inferences to events that are not precepts, wherever such inferences
are logically justifiable. Particular colours and sounds and so on are
events; their causal antecedents in the inanimate world are also events.

If we assume, as I propose to do, that every event has only a finite
number of parts, then every event is composed of a finite number of
events that have no parts. Such events I shall call “minimal events.”
It will simplify our discussion to assume them, but by a little
circumlocution this assumption could be eliminated. The reader must not
therefore regard it as an essential part of what follows.

A minimal event occupies a finite region in space-time. Let us take
time alone for purposes of illustration. The event in question may
overlap in time with each of two others, although the first of these
others wholly precedes the second; for example, you may hear a long
note on the violin while you hear two short notes on the piano. (It
is not necessary to suppose that these are really minimal events; I
merely want to illustrate what is meant.) I assume that every event
is contemporaneous with events that are not contemporaneous with each
other; this is what is meant by saying that every event lasts for a
finite time, as the reader can easily convince himself if he remembers
that time is wholly relational. If we look away from the world of
physics for a moment, and confine ourselves to the world of one man’s
experience, we can easily define an “instant” in his life. It will be
a group of events, all belonging to his experience, and having the
following two properties: (1) any two of the events overlap; (2) no
event outside the group overlaps with every member of the group. By
a slightly more complicated but essentially similar method, we can
define a point-instant in space-time as a group of events having two
properties analogous to those used just now in defining an “instant”
in one biography.[13] Thus the “points” (or point-instants) that
the mathematician needs are not simple, but are structures composed
of events, made up for the convenience of the mathematician. There
will be many “points” of which a given minimal event is a member;
all these together make up the region of space-time occupied by that
event. Space-time order, as well as space-time points, results from the
relations between events.

     [13] See _The Analysis of Matter_, by the present author,
          chap. xxviii.

A piece of matter, like a space-time point, is to be constructed out of
events, but the construction is considerably more complicated, and in
the end is only an approximation to what the physicist supposes to be
really taking place. There are, at the moment, two somewhat different
views of matter, one appropriate to the study of atomic structure, the
other to the general theory of relativity as affording an explanation
of gravitation. The view appropriate to atomic structure has itself
two forms, one derived from Heisenberg, the other from De Broglie
and Schrödinger. These two forms, it is true, are mathematically
equivalent, but in words they are very different. Heisenberg regards
a piece of matter as a centre from which radiations travel outward;
the radiations are supposed really to occur, but the matter at their
centre is reduced to a mere mathematical fiction. The radiations are,
for example, such as constitute light; they are all avowedly systems
of events, not changes in the conditions or relations of “substances.”
In the De Broglie-Schrödinger system, matter consists of wave motions.
It is not necessary to the theory to postulate anything about these
wave-motions except their mathematical characteristics, but, obviously,
since they are to explain matters they cannot serve their purpose if
they consist of motions of matter. In this system also, therefore,
we are led to construct matter out of systems of events, which just
happen, and do not happen “to” matter or “to” anything else.

Gravitation, as explained by the general theory of relativity, is
reduced to “crinkles” in space-time. Space-time being, as we have
already seen, a system constructed out of events, the “crinkles” in it
are also derived from events. There is no reason to suppose that there
is a “thing” at the place where the “crinkle” is most crinkly. Thus in
this part of physics, also, matter has ceased to be a “thing” and has
become merely a mathematical characteristic of the relations between
complicated logical structures composed of events.

It was traditionally a property of substance to be permanent, and to a
considerable extent matter has retained this property in spite of its
loss of substantiality. But its permanence now is only approximate,
not absolute. It is thought that an electron and a proton can meet and
annihilate each other; in the stars this is supposed to be happening
on a large scale.[14] And even while an electron or a proton lasts,
it has a different kind of persistence from that formerly attributed
to matter. A wave in the sea persists for a longer or shorter time:
the waves that I see dashing themselves to pieces on the Cornish coast
may have come all the way from Brazil, but that does not mean that a
“thing” has travelled across the Atlantic; it means only that a certain
process of change has travelled. And just as a wave in the sea comes
to grief at last on the rocks, so an electron or a proton may come to
grief when it meets some unusual state of affairs.

     [14] See _The Analysis of Matter_, by the present author,
          chap. xxviii.

Thus “matter” has very definitely come down in the world as a result of
recent physics. It used to be the cause of our sensations: Dr. Johnson
“disproved” Berkeley’s denial of matter by kicking a stone. If he had
known that his foot never touched the stone, and that both were only
complicated systems of wave-motions, he might have been less satisfied
with his refutation. We cannot say that “matter” is the cause of our
sensations. We can say that the events which cause our sensations
usually belong to the sort of group that physicists regard as material;
but that is a very different thing. Impenetrability used to be a noble
property of matter, a kind of Declaration of Independence; now it is a
merely tautological result of the way in which matter is defined. The
events which are the real stuff of the world are not impenetrable,
since they can overlap in space-time. In a word, “matter” has become
no more than a convenient shorthand for stating certain causal laws
concerning events.

But if matter has fared badly, mind has fared little better.
The adjective “mental” is one which is not capable of any exact
significance. There is, it is true, an important group of events,
namely percepts, all of which may be called “mental”. But it would be
arbitrary to say that there are no “mental” events except percepts,
and yet it is difficult to find any principle by which we can decide
what other events should be included. Perhaps the most essential
characteristics of mind are introspection and memory. But memory
in some of its forms is, as we have seen, a consequence of the law
of conditioned reflexes, which is at least as much physiological
as psychological, and characterises living tissue rather than
mind. Knowledge, as we have found, is not easy to distinguish from
sensitivity, which is a property possessed by scientific instruments.
Introspection is a form of knowledge, but turns out, on examination, to
be little more than a cautious interpretation of ordinary “knowledge”.
Where the philosopher’s child at the Zoo says “There is a hippopotamus
over there”, the philosopher should reply: “There is a coloured pattern
of a certain shape, which may perhaps be connected with a system of
external causes of the sort called a hippopotamus”. (I do not live up
to this precept myself.) In saying that there is a coloured pattern,
the philosopher is practising introspection in the only sense that I
can attach to that term, _i.e._ his knowledge-reaction is to an event
situated in his own brain from the standpoint of physical space, and
is consciously avoiding physiological and other inference as far as
possible. Events to which a knowledge-reaction of this sort occurs are
“mental”; so are, presumably, other events resembling them in certain
respects. But I do not see any way of defining this wider group except
by saying that mental events are events in a living brain, or, better,
in a region combining sensitivity and the law of learned reactions to
a marked extent. This definition has at least the merit of showing that
mentality is an affair of causal laws, not of the quality of single
events, and also that mentality is a matter of degree.

Perhaps it is not unnecessary to repeat, at this point, that events in
the brain are not to be regarded as consisting of motions of bits of
matter. Matter and motion, as we have seen, are logical constructions
using events as their material, and events are therefore something
quite different from matter in motion. I take it that, when we have
a percept, just what we perceive (if we avoid avoidable sources of
error) is an event occupying part of the region which, for physics, is
occupied by the brain. In fact, perception gives us the most concrete
knowledge we possess as to the stuff of the physical world, but what
we perceive is part of the stuff of our brains, not part of the stuff
of tables and chairs, sun, moon, and stars. Suppose we are looking at
a leaf, and we see a green patch. This patch is not “out there” where
the leaf is, but is an event occupying a certain volume in our brains
during the time that we see the leaf. Seeing the leaf consists of
the existence, in the region occupied by our brain, of a green patch
causally connected with the leaf, or rather with a series of events
emanating from the place in physical space where physics places the
leaf. The percept is one of this series of events, differing from the
others in its effects owing to the peculiarities of the region in
which it occurs--or perhaps it would be more correct to say that the
different effects _are_ the peculiarities of the region.

Thus “mind” and “mental” are merely approximate concepts, giving a
convenient shorthand for certain approximate laws. In a completed
science, the word “mind” and the word “matter” would both disappear,
and would be replaced by causal laws concerning “events”, the only
events known to us otherwise than in their mathematical and causal
properties being percepts, which are events situated in the same
region as a brain and having effects of a peculiar sort called
“knowledge-reactions”.

It will be seen that the view which I am advocating is neither
materialism nor mentalism, but what we call “neutral monism”. It is
monism in the sense that it regards the world as composed of only one
_kind_ of stuff, namely events; but it is pluralism in the sense that
it admits the existence of a great multiplicity of events, each minimal
event being a logically self-subsistent entity.

There is, however, another question, not quite the same as this, namely
the question as to the relations of psychology and physics. If we knew
more, would psychology be absorbed in physics? or, conversely, would
physics be absorbed in psychology? A man may be a materialist and
yet hold that psychology is an independent science; this is the view
taken by Dr. Broad in his important book on _The Mind and its Place
in Nature_. He holds that a mind is a material structure, but that it
has properties which could not, even theoretically, be inferred from
those of its material constituents. He points out that structures very
often have properties which, in the present state of our knowledge,
cannot be inferred from the properties and relations of their parts.
Water has many properties which we cannot infer from those of hydrogen
and oxygen, even if we suppose ourselves to know the structure of the
molecule of water more completely than we do as yet. Properties of a
whole which cannot, even theoretically, be inferred from the properties
and relations of its parts are called by Dr. Broad “emergent”
properties. Thus he holds that a mind (or brain) has properties which
are “emergent”, and to this extent psychology will be independent of
physics and chemistry. The “emergent” properties of minds will only be
discoverable by observation of minds, not by inference from the laws
of physics and chemistry. This possibility is an important one, and it
will be worth while to consider it.

Our decision to regard a unit of matter as itself not ultimate, but an
assemblage of events, somewhat alters the form of our question as to
“emergent” properties. We have to ask: Is matter emergent from events?
Is mind emergent from events? If the former, is mind emergent from
matter, or deducible from the properties of matter, or neither? If the
latter, is matter emergent from mind or deducible from the properties
of mind, or neither? Of course, if neither mind nor matter is emergent
from events, these latter questions do not arise.

Let us coin a word, “chrono-geography”, for the science which begins
with events having space-time relations and does not assume at the
outset that certain strings of them can be treated as persistent
material units or as minds. Then we have to ask ourselves first: can
the science of matter, as it appears in physics and chemistry, be
wholly reduced to chrono-geography? If no, matter is emergent from
events; if yes, it is not emergent.

_Is matter emergent from events?_ In the present state of science it
is difficult to give a decided answer to this question. The notion
of matter, in modern physics, has become absorbed into the notion of
energy. Eddington, in his _Mathematical Theory of Relativity_ shows
that, in virtue of the laws assumed concerning events, there must
be something having the observed properties of matter and energy as
regards conservation. This he calls the “material-energy-tensor”, and
suggests that it is the reality which we sometimes call “matter” and
sometimes “energy”. To this extent, matter has been shown to be not
emergent. But the existence of electrons and protons (to the extent
that they do exist) has not yet been deduced from the general theory
of relativity, though attempts are being made and may at any moment
succeed. If and when these attempts succeed, physics will cease to be
in any degree independent of chrono-geography, but for the present
it remains in part independent. As for chemistry, although we cannot
practically reduce it all to physics, we can see how, theoretically,
this could be done, and I think it is safe to assume that it is not an
ultimately independent science.

The question we have been asking is: could we predict, theoretically,
from the laws of events that there must be material units obeying
the laws which they do in fact obey, or is this a new, logically
independent, fact? In theory we might be able to prove that it is _not_
independent, but it would be very difficult to prove that it _is_. The
present position is, broadly speaking, that the continuous properties
of the physical world can be deduced from chrono-geography, but not the
discontinuous facts, viz. electrons and protons and Planck’s quantum.
Thus for the present materiality is practically, though perhaps not
theoretically, an emergent characteristic of certain groups of events.

_Is mind emergent from events?_ This question, as yet, can hardly be
even discussed intelligently, because psychology is not a sufficiently
advanced science. There are, nevertheless, some points to be noted.
Chrono-geography is concerned only with the abstract mathematical
properties of events, and cannot conceivably, unless it is radically
transformed, prove that there are visual events, or auditory events, or
events of any of the kinds that we know by perception. In this sense,
psychology is certainly emergent from chrono-geography and also from
physics, and it is hard to see how it can ever cease to be so. The
reason for this is that our knowledge of data contains features of a
qualitative sort, which cannot be deduced from the merely mathematical
features of the space-time events inferred from data, and yet these
abstract mathematical features are all that we can legitimately infer.

The above argument decides also that mind must be emergent from matter,
if it is a material structure. No amount of physics can ever tell us
all that we do in fact know about our own percepts.

We have still to ask whether we are to regard a mind as a structure of
material units or not. If we do so regard it, we are, so far as mind is
concerned, emergent materialists in view of what we have just decided;
this is the view favoured by Dr. Broad. If we do not so regard it, we
are in no sense materialists. In favour of the materialist view, there
is the fact that, so far as our experience goes, minds only emerge in
connection with certain physical structures, namely living bodies, and
that mental development increases with a certain kind of complexity
of physical structure. We cannot set against this the argument that
minds have peculiar characteristics, for this is quite consistent with
_emergent_ materialism. If we are to refute it, it must be by finding
out what sort of group of events constitutes a mind. It is time to
address ourselves to this question.

_What is a mind?_ It is obvious, to begin with, that a mind must be a
group of mental events, since we have rejected the view that it is a
single simple entity such as the ego was formerly supposed to be. Our
first step, therefore, is to be clear as to what we mean by a “mental”
event.

We said a few pages ago that: _Mental events are events in a region
combining sensitivity and the law of learned reactions to a marked
extent_. For practical purposes, this means (subject to a proviso to be
explained shortly) that a mental event is any event in a living brain.
We explained that this does not mean that a mental event consists of
matter in motion, which is what an old-fashioned physicist would regard
as the sort of event that happens in a brain. Matter in motion, we have
seen, is not an event in our sense, but a shorthand description of a
very complicated causal process among events of a different sort. But
we must say a few words in justification of our definition.

Let us consider some alternative definitions. A mental event, we might
say, is one which is “experienced.” When is an event “experienced”?
We might say: when it has “mnemic” effects, _i.e._ effects governed
by the law of association. But we saw that this law applies to purely
bodily events such as the contraction of the pupil, with which nothing
“mental” seems to be connected. Thus if our definition is to serve,
we shall have to define “experience” differently; we shall have to
say that the mnemic effects must include something that can be called
“knowledge.” This would suggest the definition: A mental event is
anything that is remembered. But this is too narrow: we only remember
a small proportion of our mental events. We might have regarded
“consciousness” as the essence of mental events, but this view was
examined and found inadequate in Chapter XX. Moreover, we do not want
our definition to exclude the “unconscious”.

It is clear that the primary mental events, those about which there can
be no question, are percepts. But percepts have certain peculiar causal
properties, notably that they give rise to knowledge-reactions, and
that they are capable of having mnemic effects which are cognitions.
These causal properties, however, belong to some events which are not
apparently percepts. It seems that any event in the brain may have
these properties. And perhaps we were too hasty in saying that the
contraction of the pupil on hearing a loud noise involves nothing
“mental”. There may be other “mental” events connected with a human
body besides those belonging to the central personality. I shall come
back to this possibility presently. Meanwhile, I shall adhere to the
above definition of a “mental” event, which, as we saw, makes mentality
a matter of degree.

We can now return to the question: What is a mind? There may be mental
events not forming part of the sort of group that we should call a
“mind”, but there certainly are groups having that kind of unity that
make us call them one mind. There are two marked characteristics of
a mind: First, it is connected with a certain body; secondly, it has
the unity of one “experience”. The two _prima facie_ diverge in cases
of dual or multiple personality, but I think this is more apparent
than real. These two characteristics are, one physical, the other
psychological. Let us consider each in turn as a possible definition of
what we mean by one “mind”.

In the physical way, we begin by observing that every mental event
known to us is also part of the history of a living body, and we define
a “mind” as the group of mental events which form part of the history
of a certain living body. The definition of a living body is chemical,
and the reduction of chemistry to physics is clear in theory, though
in practice the mathematics is too difficult. It is so far a merely
empirical fact that mnemic causation is almost exclusively associated
with matter having a certain chemical structure. But the same may be
said of magnetism. As yet, we cannot deduce the magnetic properties of
iron from what we know of the structure of the atom of iron, but no one
doubts that they could be deduced by a person with sufficient knowledge
and sufficient mathematical skill. In like manner it may be assumed
that mnemic causation is theoretically deducible from the structure of
living matter. If we knew enough, we might be able to infer that some
other possible structure would exhibit mnemic phenomena, perhaps in an
even more marked degree; if so, we might be able to construct Robots
who would be more intelligent than we are.

In the psychological way of defining a “mind”, it consists of all the
mental events connected with a given mental event by “experience”,
_i.e._ by mnemic causation, but this definition needs a little
elaboration before it can be regarded as precise. We do not want the
contraction of the pupil to count as a “mental” event; therefore a
mental event will have to be one which has mnemic effects, not merely
mnemic causes. In that case, however, there cannot be a last mental
event in a man’s life, unless we assume that it may have mnemic effects
on his body after death. Perhaps we may avoid this inconvenience by
discovering the _kind_ of event that usually has mnemic effects, though
they may be prevented from occurring by special circumstances. Or we
might maintain that death is gradual, even when it is what is called
instantaneous; in that case the last events in a man’s life grow
progressively less mental as life ebbs. Neglecting this point, which is
not very important, we shall define the “experience” to which a given
mental event belongs as all those mental events which can be reached
from the given event by a mnemic causal chain, which may go backwards
or forwards, or alternately first one and then the other. This may be
conceived on the analogy of an engine shunting at a junction or where
there are many points: any line that can be reached, by however many
shuntings, will count as part of the same experience.

We cannot be sure that all the mental events connected with one body
are connected by links of mnemic causation with each other, and
therefore we cannot be sure that our two definitions of one “mind”
give the same result. In cases of multiple personality, some at least
of the usual mnemic effects, notably recollection, are absent in the
life of one personality when they have occurred in the life of the
other. But probably both personalities are connected by mnemic chains
with events which occurred before the dissociation took place, so that
there would be only one mind according to our definition. But there
are other possibilities which must be considered. It may be that each
cell in the body has its own mental life, and that only selections from
these mental lives go to make up the life which we regard as ours.
The “unconscious” might be the mental lives of subordinate parts of
the body, having occasional mnemic effects which we can notice, but
in the main separate from the life of which we are “conscious”. If
so, the mental events connected with one body will be more numerous
than the events making up its central “mind”. These, however, are only
speculative possibilities.

I spoke a moment ago of the life of which we are “conscious”, and
perhaps the reader has been wondering why I have not made more use of
the notion of “consciousness”. The reason is that I regard it as only
one kind of mnemic effect, and not one entitled to a special place.
To say that I am “conscious” of an event is to say that I recollect
it, at any rate for a short time after it has happened. To say that I
recollect an event is to say that a certain event is occurring in me
now which is connected by mnemic causation with the event recollected,
and is of the sort that we call a “cognition” of that event. But
events which I do not recollect may have mnemic effects upon me. This
is the case, not only where we have Freudian suppression, but in all
habits which were learnt long ago and have now become automatic, such
as writing and speaking. The emphasis upon consciousness has made a
mystery of the “unconscious”, which ought to be in no way surprising.

It does not much matter which of our two definitions of a “mind” we
adopt. Let us, provisionally, adopt the first definition, so that a
mind is all the mental events which form part of the history of a
certain living body, or perhaps we should rather say a living brain.

We can now tackle the question which is to decide whether we are
emergent materialists or not, namely:

_Is a mind a structure of material units?_

I think it is clear that the answer to this question is in the
negative. Even if a mind consists of all the events in a brain, it
does not consist of bundles of these events grouped as physics groups
them, _i.e._ it does not lump together all the events that make up
one piece of matter in the brain, and then all the events that make
up another, and so on. Mnemic causation is what concerns us most in
studying mind, but this seems to demand a recourse to physics, if we
assume, as seems plausible, that mental mnemic causation is due to
effects upon the brain. This question, however, is still an open one.
If mnemic causation is ultimate, mind is emergent. If not, the question
is more difficult. As we saw earlier, there certainly is knowledge in
psychology which cannot ever form part of physics. But as this point is
important, I shall repeat the argument in different terms.

The difference between physics and psychology is analogous to that
between a postman’s knowledge of letters and the knowledge of a
recipient of letters. The postman knows the movements of many letters,
the recipient knows the contents of a few. We may regard the light and
sound waves that go about the world as letters of which the physicist
may know the destination; some few of them are addressed to human
beings, and when read give psychological knowledge. Of course the
analogy is not perfect, because the letters with which the physicist
deals are continually changing during their journeys, as if they were
written in fading ink, which, also, was not quite dry all the time,
but occasionally got smudged with rain. However, the analogy may pass
if not pressed.

It would be possible without altering the detail of previous
discussions, except that of Chapter XXV, to give a different turn
to the argument, and make matter a structure composed of mental
units. I am not quite sure that this is the wrong view. It arises not
unnaturally from the argument as to data contained in Chapter XXV. We
saw that all data are mental events in the narrowest and strictest
sense, since they are percepts. Consequently all verification of causal
laws consists in the occurrence of expected percepts. Consequently any
inference beyond percepts (actual or possible) is incapable of being
empirically tested. We shall therefore be prudent if we regard the
non-mental events of physics as mere auxiliary concepts, not assumed
to have any reality, but only introduced to simplify the laws of
percepts. Thus matter will be a construction built out of percepts, and
our metaphysic will be essentially that of Berkeley. If there are no
non-mental events, causal laws will be very odd; for example, a hidden
dictaphone may record a conversation although it did not exist at the
time, since no one was perceiving it. But although this seems odd, it
is not logically impossible. And it must be conceded that it enables
us to interpret physics with a smaller amount of dubious inductive and
analogical inference than is required if we admit non-mental events.

In spite of the logical merits of this view, I cannot bring myself
to accept it, though I am not sure that my reasons for disliking it
are any better than Dr. Johnson’s. I find myself constitutionally
incapable of believing that the sun would not exist on a day when he
was everywhere hidden by clouds, or that the meat in a pie springs into
existence at the moment when the pie is opened. I know the logical
answer to such objections, and _qua logician_ I think the answer a good
one. The logical argument, however, does not even tend to show that
there are _not_ non-mental events; it only tends to show that we have
no right to feel sure of their existence. For my part, I find myself
in fact believing in them in spite of all that can be said to persuade
me that I ought to feel doubtful.

There is an argument, of a sort, against the view we are considering.
I have been assuming that we admit the existence of other people and
their perceptions, but question only the inference from perceptions to
events of a different kind. Now there is no good reason why we should
not carry our logical caution a step further. I cannot verify a theory
by means of another man’s perceptions, but only by means of my own.
Therefore the laws of physics can only be verified by me in so far as
they lead to predictions of _my_ percepts. If then, I refuse to admit
non-mental events because they are not verifiable, I ought to refuse
to admit mental events in every one except myself, on the same ground.
Thus I am reduced to what is called “solipsism”, _i.e._ the theory that
I alone exist. This is a view which is hard to refute, but still harder
to believe. I once received a letter from a philosopher who professed
to be a solipsist, but was surprised that there were no others! Yet
this philosopher was by way of believing that no one else existed. This
shows that solipsism is not really believed even by those who think
they are convinced of its truth.

We may go a step further. The past can only be verified indirectly,
by means of its effects in the future; therefore the type of logical
caution we have been considering should lead us to abstain from
asserting that the past really occurred: we ought to regard it as
consisting of auxiliary concepts convenient in stating the laws
applicable to the future. And since the future, though verifiable if
and when it occurs, is as yet unverified, we ought to suspend judgment
about the future also. If we are not willing to go so far as this,
there seems no reason to draw the line at the precise point where it
was drawn by Berkeley. On these grounds I feel no shame in admitting
the existence of non-mental events such as the laws of physics lead us
to infer. Nevertheless, it is important to realise that other views are
tenable.




CHAPTER XXVII

MAN’S PLACE IN THE UNIVERSE


In this final chapter, I propose to recapitulate the main conclusions
at which we have arrived, and then to say a few words on the subject of
Man’s relation to the universe in so far as philosophy has anything to
teach on this subject without extraneous help.

Popular metaphysics divides the known world into mind and matter, and
a human being into soul and body. Some--the materialists--have said
that matter alone is real and mind is an illusion. Many--the idealists
in the technical sense, or mentalists, as Dr. Broad more appropriately
calls them--have taken the opposite view, that mind alone is real and
matter is an illusion. The view which I have suggested is that both
mind and matter are structures composed of a more primitive stuff which
is neither mental nor material. This view, called “neutral monism”,
is suggested in Mach’s _Analysis of Sensations_, developed in William
James’s _Essays in Radical Empiricism_, and advocated by John Dewey,
as well as by Professor R. B. Parry and other American realists. The
use of the word “neutral” in this way is due to Dr. H. M. Sheffer,[15]
formerly of Harvard, who is one of the ablest logicians of our time.

     [15] See Holt’s _Concept of Consciousness_, preface.

Since man is the instrument of his own knowledge, it is necessary to
study him as an instrument before we can appraise the value of what our
senses seem to tell us concerning the world. In Part I we studied man,
within the framework of common-sense beliefs, just as we might study
clocks or thermometers, as an instrument sensitive to certain features
of the environment, since sensitiveness to the environment is obviously
an indispensable condition for knowledge about it.

In Part II we advanced to the study of the physical world. We
found that matter, in modern science, has lost its solidity and
substantiality; it has become a mere ghost haunting the scenes of
its former splendours. In pursuit of something that could be treated
as substantial, physicists analysed ordinary matter into molecules,
molecules into atoms, atoms into electrons and protons. There, for
a few years, analysis found a resting-place. But now electrons and
protons themselves are dissolved into systems of radiations by
Heisenberg, and into systems of waves by Schrödinger--the two theories
amount mathematically to much the same thing. And these are not wild
metaphysical speculations; they are sober mathematical calculations,
accepted by the great majority of experts.

Another department of theoretical physics, the theory of relativity,
has philosophical consequences which are, if possible, even more
important. The substitution of space-time for space and time has
made the category of substance less applicable than formerly, since
the essence of substance was persistence through time, and there is
now no one cosmic time. The result of this is to turn the physical
world into a four-dimensional continuum of events, instead of a
series of three-dimensional states of a world composed of persistent
bits of matter. A second important feature of relativity-theory is
the abolition of force, particularly gravitational force, and the
substitution of differential causal laws having to do only with the
neighbourhood of an event, not with an influence exerted from a
distance, such as gravitation formerly seemed to be.

The modern study of the atom has had two consequences which have
considerably changed the philosophical hearing of physics. On the
one hand, it appears that there are discontinuous changes in nature,
occasions when there is a sudden jump from one state to another without
passing through the intermediate states. (Schrödinger, it is true,
questions the need for assuming discontinuity; but so far his opinion
has not prevailed.) On the other hand, the course of nature is not so
definitely determined by the physical laws at present known as it was
formerly thought to be. We cannot predict when a discontinuous change
will take place in a given atom, though we can predict statistical
averages. It can no longer be said that, given the laws of physics and
the relevant facts about the environment, the future history of an atom
can theoretically be calculated from its present condition. It may be
that this is merely due to the insufficiency of our knowledge, but we
cannot be sure that this is the case. As things stand at present, the
physical world is not so rigidly deterministic as it has been believed
to be during the last 250 years. And in various directions what
formerly appeared as laws governing each separate atom are now found to
be only averages attributable in part to the laws of chance.

From these questions concerning the physical world in itself, we were
led to others concerning the causation of our perceptions, which are
the data upon which our scientific knowledge of physics is based. We
saw that a long causal chain always intervenes between an external
event and the event in us which we regard as perception of the
external event. We cannot therefore suppose that the external event
is exactly what we see or hear; it can, at best, resemble the percept
only in certain structural respects. This fact has caused considerable
confusion in philosophy, partly because philosophers tried to think
better of perception than it deserves, partly because they failed to
have clear ideas on the subject of space. It is customary to treat
space as a characteristic of matter as opposed to mind, but this is
only true of _physical_ space. There is also _perceptual_ space,
which is that in which what we know immediately through the senses is
situated. This space cannot be identified with that of physics. From
the standpoint of physical space, all our percepts are in our heads;
but in perceptual space our percept of our hand is outside our percept
of our head. The failure to keep physical and perceptual space distinct
has been a source of great confusion in philosophy.

In Part III we resumed the study of man, but now as he appears to
himself, not only as he is known to an external observer. We decided,
contrary to the view of the behaviourists, that there are important
facts which cannot be known except when the observer and observed are
the same person. The datum in perception, we decided, is a private fact
which can only be known directly to the percipient; it is a datum for
physics and psychology equally, and must be regarded as both physical
and mental. We decided later that there are inductive grounds, giving
probability but not certainty, in favour of the view that perceptions
are causally connected with events which the percipient does not
experience, which may belong only to the physical world.

The behaviour of human beings is distinguished from that of inanimate
matter by what are called “mnemic” phenomena, _i.e._ by a certain kind
of effect of past occurrences. This kind of effects is exemplified in
memory, in learning, in the intelligent use of words, and in every
kind of knowledge. But we cannot, on this ground, erect an absolute
barrier between mind and matter. In the first place, inanimate matter,
to some slight extent, shows analogous behaviour--_e.g._ if you unroll
a roll of paper, it will roll itself up again. In the second place, we
find that living bodies display mnemic phenomena to exactly the same
extent to which minds display them. In the third place, if we are to
avoid what I have called “mnemic” causation, which involves action at
a distance in time, we must say that mnemic phenomena in mental events
are due to the modification of the body by past events. That is to
say, the set of events which constitutes one man’s experience is not
causally self-sufficient, but is dependent upon causal laws involving
events which he cannot experience.

On the other hand, our knowledge of the physical world is purely
abstract: we know certain logical characteristics of its structure,
but nothing of its intrinsic character. There is nothing in physics
to prove that the intrinsic character of the physical world differs,
in this or that respect, from that of the mental world. Thus from
both ends, both by the analysis of physics and by the analysis of
psychology, we find that mental and physical events form one causal
whole, which is not known to consist of two different sorts. At
present, we know the laws of the physical world better than those of
the mental world, but that may change. We know the intrinsic character
of the mental world to some extent, but we know absolutely nothing
of the intrinsic character of the physical world. And in view of the
nature of the inferences upon which our knowledge of physics rests, it
seems scarcely possible that we should ever know more than abstract
laws about matter.

In Part IV we considered what philosophy has to say about the universe.
The function of philosophy, according to the view advocated in this
volume, is somewhat different from that which has been assigned to it
by a large and influential school. Take, _e.g._ Kant’s antinomies.
He argues (1) that space must be infinite, (2) that space cannot be
infinite; and he deduces that space is subjective. The non-Euclideans
refuted the argument that it must be infinite, and Georg Cantor refuted
the argument that it cannot be. Formerly, _a priori_ logic was used to
prove that various hypotheses which looked possible were impossible,
leaving only one possibility, which philosophy therefore pronounced
true. Now _a priori_ logic is used to prove the exact contrary, namely,
that hypotheses which looked impossible are possible. Whereas logic
was formerly counsel for the prosecution, it is now counsel for the
defence. The result is that many more hypotheses are at large than
was formerly the case. Formerly, to revert to the instance of space,
it appeared that experience left only one kind of space to logic, and
logic showed this one kind to be impossible. Now, logic presents many
kinds of space as possible apart from experience, and experience only
partially decides between them. Thus, while our knowledge of what is
has become less than it was formerly supposed to be, our knowledge of
what may be is enormously increased. Instead of being shut in within
narrow walls, of which every nook and cranny could be explored, we find
ourselves in an open world of free possibilities, where much remains
unknown because there is so much to know. The attempt to prescribe
to the universe by means of _a priori_ principles has broken down;
logic, instead of being, as formerly, a bar to possibilities, has
become the great liberator of the imagination, presenting innumerable
alternatives which are closed to unreflective common sense, and leaving
to experience the task of deciding, where decision is possible, between
the many worlds which logic offers for our choice.

Philosophical knowledge, if what we have been saying is correct, does
not differ essentially from scientific knowledge; there is no special
source of wisdom which is open to philosophy but not to science, and
the results obtained by philosophy are not radically different from
those reached in science. Philosophy is distinguished from science only
by being more critical and more general. But when I say that philosophy
is critical, I do not mean that it attempts to criticise knowledge from
outside, for that would be impossible: I mean only that it examines
the various parts of our supposed knowledge to see whether they are
mutually consistent and whether the inferences employed are such as
seem valid to a careful scrutiny. The criticism aimed at is not that
which, without reason, determines to reject, but that which considers
each piece of apparent knowledge on its merits and retains whatever
still appears to be knowledge when this consideration is completed.
That some risk of error remains must be admitted, since human beings
are fallible. Philosophy may claim justly that it diminishes the risk
of error, and that in some cases it renders the risk so small as to be
practically negligible. To do more than this is not possible in a world
where mistakes must occur; and more than this no prudent advocate of
philosophy would claim to have performed.

I want to end with a few words about man’s place in the universe. It
has been customary to demand of a philosopher that he should show that
the world is good in certain respects. I cannot admit any duty of this
sort. One might as well demand of an accountant that he should show
a satisfactory balance sheet. It is just as bad to be fraudulently
optimistic in philosophy as in money matters. If the world is good,
by all means let us know it; but if not, let us know that. In any
case, the question of the goodness or badness of the world is one for
science rather than for philosophy. We shall call the world good if
it has certain characteristics that we desire. In the past philosophy
professed to be able to prove that the world had such characteristics,
but it is now fairly evident that the proofs were invalid. It does not,
of course, follow that the world does not have the characteristics in
question; it follows only that philosophy cannot decide the problem.
Take for example the problem of personal immortality. You may believe
this on the ground of revealed religion, but that is a ground which
lies outside philosophy. You may believe it on the ground of the
phenomena investigated by psychical research, but that is science, not
philosophy. In former days, you could believe it on a philosophical
ground, namely, that the soul is a substance and all substances are
indestructible. You will find this argument, sometimes more or less
disguised, in many philosophers. But the notion of substance, in
the sense of a permanent entity with changing states, is no longer
applicable to the world. It may happen, as with the electron, that a
string of events are so interconnected causally that it is practically
convenient to regard them as forming one entity, but where this happens
it is a scientific fact, not a metaphysical necessity. The whole
question of personal immortality, therefore lies outside philosophy,
and it is to be decided, if at all, either by science or by revealed
religion.

I will take up another matter in regard to which what I have said may
have been disappointing to some readers. It is sometimes thought that
philosophy ought to aim at encouraging a good life. Now, of course,
I admit that it should have this effect, but I do not admit that it
should have this as a conscious purpose. To begin with, when we embark
upon the study of philosophy we ought not to assume that we already
know for certain what the good life is; philosophy may conceivably
modify our views as to what is good, in which case it will seem to
the non-philosophical to have had a bad moral effect. That, however,
is a secondary point. The essential thing is that philosophy is part
of the pursuit of knowledge, and that we cannot limit this pursuit by
insisting that the knowledge obtained shall be such as we should have
thought edifying before we obtained it. I think it could be maintained
with truth that _all_ knowledge is edifying, provided we have a right
conception of edification. When this appears to be not the case it is
because we have moral standards based upon ignorance. It may happen by
good fortune that a moral standard based upon ignorance is right, but
if so knowledge will not destroy it; if knowledge can destroy it, it
must be wrong. The conscious purpose of philosophy, therefore, ought
to be solely to _understand_ the world as well as possible, not to
establish this or that proposition which is thought morally desirable.
Those who embark upon philosophy must be prepared to question all
their preconceptions, ethical as well as scientific; if they have a
determination never to surrender certain philosophic beliefs, they are
not in the frame of mind in which philosophy can be profitably pursued.

But although philosophy ought not to have a moral purpose, it ought
to have certain good moral effects. Any disinterested pursuit of
knowledge teaches us the limits of our power, which is salutary; at
the same time, in proportion as we succeed in achieving knowledge, it
teaches the limits of our impotence, which is equally desirable. And
philosophical knowledge, or rather philosophical thought, has certain
special merits not belonging in an equal degree to other intellectual
pursuits. By its generality it enables us to see human passions in
their just proportions, and to realise the absurdity of many quarrels
between individuals, classes, and nations. Philosophy comes as near
as possible for human beings to that large, impartial contemplation of
the universe as a whole which raises us for the moment above our purely
personal destiny. There is a certain asceticism of the intellect which
is good as a part of life, though it cannot be the whole so long as
we have to remain animals engaged in the struggle for existence. The
asceticism of the intellect requires that, while we are engaged in the
pursuit of knowledge, we shall repress all other desires for the sake
of the desire to know. While we are philosophising, the wish to prove
that the world is good, or that the dogmas of this or that sect are
true, must count as weaknesses of the flesh--they are temptations to
be thrust on one side. But we obtain in return something of the joy
which the mystic experiences in harmony with the will of God. This joy
philosophy can give, but only to those who are willing to follow it to
the end, through all its arduous uncertainties.

The world presented for our belief by a philosophy based upon modern
science is in many ways less alien to ourselves than the world of
matter as conceived in former centuries. The events that happen in
our minds are part of the course of nature, and we do not know that
the events which happen elsewhere are of a totally different kind.
The physical world, so far as science can show at present, is perhaps
less rigidly determined by causal laws than it was thought to be;
one might, more or less fancifully, attribute even to the atom a
kind of limited free will. There is no need to think of ourselves as
powerless and small in the grip of vast cosmic forces. All measurement
is conventional, and it would be possible to devise a perfectly
serviceable system of measurement according to which a man would be
larger than the sun. No doubt there are limits to our power, and it
is good that we should recognise the fact. But we cannot say what
the limits are, except in a quite abstract way, such as that we
cannot create energy. From the point of view of human life, it is
not important to be able to _create_ energy; what is important is to
be able to direct energy into this or that channel, and this can do
more and more as our knowledge of science increases. Since men first
began to think, the forces of nature have oppressed them; earthquakes,
floods, pestilences, and famines have filled them with terror. Now at
last, thanks to science, mankind is discovering how to avoid much of
the suffering that such events have hitherto entailed. The mood in
which, as it seems to me the modern man should face the universe is
one of quiet self-respect. The universe as known to science is not in
itself either friendly or hostile to man, but it can be made to act as
a friend if approached with patient knowledge. Where the universe is
concerned, knowledge is the one thing needful. Man, alone of living
things, has shown himself capable of the knowledge required to give
him a certain mastery over his environment. The dangers to man in the
future, or at least in any measurable future, come, not from nature,
but from man himself. Will he use his power wisely? Or will he turn
the energy liberated from the struggle with nature into struggles with
his fellow-men? History, science, and philosophy all make us aware
of the great collective achievements of mankind. It would be well if
every civilised human being had a sense of these achievements and a
realisation of the possibility of greater things to come, with the
indifference which must result as regards the petty squabbles upon
which the passions of individuals and nations are wastefully squandered.

Philosophy should make us know the ends of life, and the elements in
life that have value on their own account. However our freedom may
be limited in the causal sphere, we need admit no limitations to our
freedom in the sphere of values: what we judge good on its own account
we may continue to judge good, without regard to anything but our own
feeling. Philosophy cannot itself determine the ends of life, but it
can free us from the tyranny of prejudice and from distortions due
to a narrow view. Love, beauty, knowledge, and joy of life: these
things retain their lustre however wide our purview. And if philosophy
can help us to feel the value of these things, it will have played
its parts in man’s collective work of bringing light into a world of
darkness.




INDEX


  Æther or empty space, 107

  Analogy, positive and negative, 271

  _Analysis of Sensations_ (Mach), 292

  _Animal Intelligence_ (Thorndike), 30

  Animal learning, study of, 29 ff.
    Thorndike’s laws of, 31 f.
    learned reactions, 35 f.

  _A priori_, causation not regarded as, 150
    knowledge, 249 f., 265
    probability, on Keynes’s theory, is, 274
    logic, 296

  Aristotle, 226

  Association, principle of, 33 f., 48, 64, 180

  Aston, Dr. F. W., 99

  Atom, theory of the, 98 ff.
    centre from which radiations travel, 157
    philosophical consequences of modern study of the, 293

  Attention, 205


  Bacon, 80

  Behaviourism, its view of man, 70 ff.
    where it breaks down as a final philosophy, 129
    dilemma put to, 133
    its propositions as to thought examined, 169 ff.
    and logic, 263

  _Behaviourism_ (Watson), 22, 31, 33

  “Belief”, 254, 258 ff.
    definition of, 261

  Beliefs, defects in common, 3 ff.

  Bergson, 71, 73, 198

  Berkeley, 246 f.

  _Bodily Changes in Pain, Hunger, Fear and Rage_ (Cannon), 218

  Body, human, 25, 139

  Bohr, Niels, his addition to the theory of atoms, 101 ff.

  Bradley, monistic view of, 251
    criticism of his argument against relations, 252

  Braithwaite, R. B., 269

  Brentano, 202

  Broad, Dr., 188, 195, 282, 292

  Buddha, 227

  Butler, Samuel, 71


  Cannon, 218

  Cantor, Georg, 296

  Casuistry, 225

  Causation, as an _a priori_ belief, 5, 150
    notion of “necessary” sequence, 115
    conception of, in science, 144 ff.

  “Cause”, Kant’s category of, 248 f.

  “Chrono-geography”, 283

  Cognition, 61, 202 f., 217

  Conation, 202

  Conception, 203

  “Conditioned reflexes”, 35

  Confucius, 227

  Conscience, 228

  “Consciousness”, 60
    William James’s views on, 210
    two different meanings of the word, 210
    criticism of common sense view of, 211 ff.
    self, 214
    William James’s views approved, 217
    one kind of mnemic effect, 288

  Continuity in nature, 108

  Correlation, laws of, 117

  _Critique of Practical Reason_ (Kant), 249

  Curiosity, 220


  Dalton, 98

  “Data”, 266 f., 276

  De Broglie, 278

  Decalogue, the, 227

  Descartes, 9, 162 ff., 237 ff.

  Desire, behaviourist view of, 90 f.
    introspective view of, 221 ff.

  Dewey, John, 292

  Discontinuity in nature, 101, 106, 108

  Dreams, 62, 127, 175, 176, 185, 189, 193

  Dualism of mind and matter, 141, 239

  Ductless glands, the, 218


  Eddington, Professor, 273, 279

  Education, 233

  Einstein, 96, 116, 239, 242, 249

  Electron, 99 ff., 118, 145

  “Emergent” properties, 282

  Emotions, essential physiological conditions of the, 118
    subject to “Conditioning”, 119
    generate irrational opinions, 120

  Energy, radiation of, from matter into empty space, 145
    propagation in empty space, 145
    impact on matter in empty space, 146

  _Essays in Radical Empiricism_ (William James), 210, 292

  Ethics, views of the ancients on, 227
    theory that virtue consists in obedience to authority, 227 ff.
    utilitarian theory of, 229 f.
    the concept of “good”, 230
    mainly social, 233
    the supreme moral rule, 234 f.

  Events, in physics, 110 f.
    string of, 118 f.
    “mental”, 141, 280 ff.
    structure and mathematical laws of, 157
    minimal, 277
    matter constructed out of, 278

  Experience, effects of, in a reaction to stimulus, 180 ff.


  Familiarity, a stage in memory, 195 f.

  Fear and Rage, 219

  Feeling, as mental occurrence, 202

  Forces, 111, 114, 117, 120 f.

  Form, reaction to, 85 f.

  Freudian “unconscious” the, 221


  Galileo, 80

  Generalisations, 271 f.

  Geodesic, 112, 117

  Geometry, as empirical as geography, 249 f.

  _Gestaltpsychologie_, 37, 41, 43, 68, 247

  Gravitation, 116 f., 145, 279

  Griffith, Mr. Percy, 118


  Habit-formation, 36

  Habit-memory, 188, 196

  Hegel, 227, 229, 251

  Heisenberg, 96, 105, 278, 293

  Heisenberg-Schrödinger theories of atomic structure, 243

  Heraclitus, 251

  Huc, Monsieur, 232

  Hume, 180, 191, 247 f.


  Images, visual, auditory and tactual, 176
    behaviourist explanation of, 177 f.
    difference between sensations and, 179 ff.
    definition of, 184 f.
    first stage in memory, 195

  Imagination, analysis of, 190 ff.
    essence of, 191
    exceptional gifts of, 193
    and belief, 193 f.
    difference between memory and, 194

  Induction problem of validity of, 14
    as a practice, 80 f.
    principle of, 268 f.
    logical problem of, 269 ff.
    Mr. Keynes’s examination of, 270 ff.

  Inference, “physiological”, 13, 80 ff., 135
    syllogistic, 79
    inductive and mathematical, 83 ff.

  “Innate ideas”, doctrine of, 245

  Interval, space-like and time-like, 110 f.

  Introspection, 10, 11, 12, 172 f., 201 ff.


  James, William, 210, 223.


  Kant, 80, 201, 239, 248, 296

  Keynes Mr., on problems of induction, 269 ff.

  Köhler, 37 ff.

  Knowing, as mental occurrence, 202

  Knowledge, as displayed in reactions to environment, 17 ff.
    perceptual, 58 ff.
    behaviourist view of, 88 ff.
    difference between introspective and other, 215
    _a priori_, 249 f.
    limitations on, imposed by structure of language, 264 f.

  Knowledge-reaction, 216, 282


  Language, as a bodily habit, 43 ff.
    psychological side of, 48
    words in an ideal logical, 256 f.
    and things, relation between, 264

  Laws, causal, 144 ff.
    evidence for, 147
    universal characteristics of, 149

  Learning, laws of, 23, 29 ff.
    two ways of, 39
    in infants, 41, 48
    by increase of sensitivity, 95 f.

  Leibniz, 239, 241 f.

  _Le Problème logique de l’induction_ (Jean Nicod), 269, 273

  Locke, 244 ff.

  Logic, 263, 296

  “Logical atomism”, 248


  Mach, 214, 292

  Man, his relation to the Universe, 292, 295, 298 ff.

  Materialism, as a philosophy, 159

  _Mathematical Theory of Relativity_ (Eddington), 283

  Matter, the structure of the atom, 98 ff.
    essence of, 146 f.
    as conceived in modern physics, 157, 293
    old view of, now untenable, 158 ff.
    constructed out of events, 278
    permanence of, only approximate, 279
    possibly a structure of mental units, 290

  Maxwell’s equations, 107, 145

  Meaning, 52, 71, 82

  Meinong, 202

  Memory, behaviourist theory of, 71 ff.
    its reference to the past, 188 ff.
    feeling of pastness complex, 190
    more fundamental than imagination, 190
    vital difference between imagination and, 194
    Dr. Broad’s view on reference to the past, 195
    stages of, 195 ff.
    immediate, 196 f.
    true recollection, 197 ff.
    trustworthiness of, 199

  Memory and testimony, 5 ff.

  Mendeleev, 99

  “Mental” events, 114, 141 f., 280 f.

  “Mental” occurrences, 201, 212

  _Mentality of Apes_ (Köhler), 37 ff., 62

  Mill, J. S., his canons of induction, 269 f.

  Mind and matter, conventional notions of, 141
    distinction between, illusory, 142, 201
    gap between, how filled in, 148
    interaction between, 150
    theory of “neutral monism”, 206 ff.
    Cartesian dualism, 239
    Leibniz’s theory of, 241

  Mind, a cross-section in a stream of physical causation, 150
    modern conception of, 280 ff.
    emergent from events, 284
    definitions of a, 285 ff.

  Minkowski, 239

  _Mneme_ (Semon), 49

  “Mnemic” effects, 49, 209, 295

  “Mnemic” occurrences, 49, 180 f.

  Monads, 241

  Monists and pluralists, controversy between, 251 ff.
    pluralism the view of science and common sense, 253

  Moore, Dr. G. E., on notion of “good”, 230

  “Moral issues”, 227

  Motion, 119, 163

  Mystics, 229, 264, 300


  Names, 53

  Necessity, anthropomorphic notion of, 115, 117

  “Neutral monism”, theory of, 206 ff., 210, 282, 292

  Newton, 242

  Nisbet, R. H., on probability, 275


  Object, what happens when we see an, 146 f.

  Objective and subjective study, 30

  Objectivity, 154 f., 169

  Ogden and Richards, Messrs., 52


  Parmenides, monistic view complete in, 251

  Parry, Professor R. B., 292

  Perception, difference between introspection and, 10 f.
    a species of sensitivity, 59, 123
    and inference, 65 f.
    from objective standpoint, 66 ff.
    of external event, analysis of, 123 ff.
    element of subjectivity in, 130 ff.
    and causal laws of physics, 145 ff.
    its relation to the object causal and mathematical, 149
    from introspective standpoint, 201 ff.

  Perceptive knowledge, stages in act of, 18 ff.

  Percepts, 133, 135, 137 ff.

  Perspective, 152

  Philosophy, the business of, 2, 236
    Behaviourism as a, 129 ff.
    Utilitarian, 229 f.
    systems of Descartes, Spinoza, and Leibniz, 237 ff.
    Locke, Berkeley, and Hume, 244 ff.
    conscious purpose of, 299

  Physics, modern, 97
    causal laws in, 114 ff., 145 ff.
    and perception, 123 ff.
    spatial relations in, 137 ff.
    our knowledge of, 151 ff.
    only mathematical properties of, discoverable, 157
    less deterministic than formerly, 239
    and psychology, 282, 289

  Pictures, as representations, 183

  “Planck’s Constant”, 101 f.

  Plato, 226

  Poetry, 220

  Probability, fundamental in science, 274
    _a priori_ on Mr. Keynes’s theory, 274
    “frequency”, theory of, 274 f.

  Psychology, 16, 172, 184
    and physics, 282, 289

  “Psychophysical parallelism”, 238

  “Public good”, the, 230

  Publicity, in the case of physical phenomena, 170


  Quantum changes, 106


  Radio-activity, 99, 103

  Reactions, learned, 21, 33, 35, 36, 49, 81

  Realism, naive, 175

  Recognition, two forms of, 196

  Recollection, true, 197 ff.

  Relations, Bradley’s argument against, 252
    cause of confusion about, 264

  Relativity, theory of, “space-time” instead of one cosmic time and
        space, 108
    some results of the, 108 ff.
    “events” instead of bodies moving, 110
    relations between “events”, 110 f.
    no “forces” in the, 111
    philosophical consequences of the, 293

  “Right conduct”, 230

  Rutherford, Sir E., 99, 101


  Santayana, Mr., 230

  Schiller, Dr. F. C. S., 79

  Schrödinger, 98, 105, 278, 293, 294

  Self-observation, 126, 161 ff.
    basis of Descartes’s system, 162 ff.
    Dr. Watson’s views, 167 ff.
    gives knowledge not part of physics, 175

  Semon, 49, 180

  Sensation, difference between images and, 179
    acoleuthic, 197
    as opposed to perception, 204

  Sensitivity, 59 f., 88, 123, 177

  Sentences, 51, 54, 75, 255, 264

  Sequence, laws of, 116

  Shakespeare, 192

  Sheffer, Dr. H. M., 282, 292

  Sight, compared with touch, 156 f.

  Size, sense of, 153

  Socrates, 226

  “Solipsism”, 291

  Sommerfeld, 103

  Space, one persistent, abolished in relativity theory, 108
    physical and perceptual, 137 ff., 241 f., 294

  Space-time, in theory of relativity, 108 ff.
    structure of, 145
    point-instant in, 278

  “Specious present”, 195, 197

  Spinoza, 238, 251

  _Stars and Atoms_ (Eddington), 279

  “Statement”, definition of a, 260

  Subjectivity, 129, 133, 135, 154 f.

  Substance, 5, 242 ff., 293

  Syllogism, the, 80

  Syntax, influence of, on philosophy, 243
    connection between laws of physics and laws of, 263


  Talking without thinking, 190

  Tendency, quantitative laws of, 144

  Testimony, 11 f., 170

  _The Analysis of Matter_ (Bertrand Russell), 278

  _The Meaning of Meaning_ (Ogden and Richards), 52

  _The Mind and Its Place in Nature_ (Dr. Broad), 76, 188, 282

  Thorndike’s “provisional laws”, 31 ff.

  Thought, 163 ff., 174, 240, 263

  Time, not cosmic, 108 ff., 158

  Touch, compared with sight, 156

  _Treatise on Probability_ (Keynes), 269 ff.

  Truth, 94, 261 f.

  Truth and Falsehood, causes of mystery about, 254
    two questions in, 254 ff.
    meaning of a sentence examined, 255 f.
    grounds on which statements are regarded as true or false, 257
    ultimate test of falsehood, 258
    “belief”, 258 ff.
    problems of, 259 ff.


  Universals, 53, 203

  Universe, the, philosophy concerned with, 236
    man’s relation to, 298 ff.

  “Unlearned Equipment”, 22

  Utilitarian philosophy, 229 f.


  Vitalists, 25

  Volition, 61


  Watson, Dr. J. B., 10, 21, 22, 31, 33, 35, 36, 37, 70 ff., 126 ff.,
        162, 167 ff., 177, 188, 219, 223, 259

  Waves in empty space, 107 f.

  Whitehead, Dr., 159

  “Will”, 223 f.

  Willing, as mental occurrence, 202

  _Winds of Doctrine_ (Santayana), 230

  Wish-fulfilment and dread-fulfilment, 194

  Wittgenstein, 264

  Words, purpose of, 11 f.
    as physical occurrences, 44 ff.
    spoken and written, 46 f.
    how acquired by infants, 48 ff.
    meaning of, 52, 256
    relations of, 56
    in an ideal logical language, 256 f.

  World, the physical, nature of our
    knowledge of, 151 ff.
    a four-dimensional continuum of events, 293
    our knowledge of, purely abstract, 295


THE END




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Transcriber’s Notes


Hyphenation, and spelling were made consistent when a predominant
preference was found in the original book; otherwise they were not
changed.

Original text mostly placed commas and periods after closing quotation
marks, but occasionally placed them before closing quotation marks.
This inconsistency has not been changed here.

Simple typographical errors were corrected; unbalanced quotation
marks were remedied when the change was obvious, and otherwise left
unbalanced.

Footnotes have been sequentially renumbered and placed just below
the paragraphs that reference them.

The index was not checked for proper alphabetization or correct page
references.

Page 86: The variables in the equation were printed in italics. To
improve readability, the underscore characters used elsewhere to
indicate italics have been omitted in this case.

Page 207: “this is a causal word” originally was printed as “this a a
causal word”; changed here by Transcriber.