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.