The Analysis of Mind, Bertrand Russell [best desktop ebook reader .txt] 📗

entities of this sort may or may not

exist, but there is no good ground for assuming that they do. The

functions that they appear to perform can always be performed by

classes or series or other logical constructions, consisting of

less dubious entities. If we are to avoid a perfectly gratuitous

assumption, we must dispense with the subject as one of the

actual ingredients of the world. But when we do this, the

possibility of distinguishing the sensation from the sense-datum

vanishes; at least I see no way of preserving the distinction.

Accordingly the sensation that we have when we see a patch of

colour simply is that patch of colour, an actual constituent of

the physical world, and part of what physics is concerned with. A

patch of colour is certainly not knowledge, and therefore we

cannot say that pure sensation is cognitive. Through its

psychological effects, it is the cause of cognitions, partly by

being itself a sign of things that are correlated with it, as

e.g. sensations of sight and touch are correlated, and partly by

giving rise to images and memories after the sensation is faded.

But in itself the pure sensation is not cognitive.

 

In the first lecture we considered the view of Brentano, that “we

may define psychical phenomena by saying that they are phenomena

which intentionally contain an object.” We saw reasons to reject

this view in general; we are now concerned to show that it must

be rejected in the particular case of sensations. The kind of

argument which formerly made me accept Brentano’s view in this

case was exceedingly simple. When I see a patch of colour, it

seemed to me that the colour is not psychical, but physical,

while my seeing is not physical, but psychical. Hence I concluded

that the colour is something other than my seeing of the colour.

This argument, to me historically, was directed against idealism:

the emphatic part of it was the assertion that the colour is

physical, not psychical. I shall not trouble you now with the

grounds for holding as against Berkeley that the patch of colour

is physical; I have set them forth before, and I see no reason to

modify them. But it does not follow that the patch of colour is

not also psychical, unless we assume that the physical and the

psychical cannot overlap, which I no longer consider a valid

assumption. If we admit—as I think we should—that the patch of

colour may be both physical and psychical, the reason for

distinguishing the sense-datum from the sensation disappears, and

we may say that the patch of colour and our sensation in seeing

it are identical.

 

This is the view of William James, Professor Dewey, and the

American realists. Perceptions, says Professor Dewey, are not per

se cases of knowledge, but simply natural events with no more

knowledge status than (say) a shower. “Let them [the realists]

try the experiment of conceiving perceptions as pure natural

events, not cases of awareness or apprehension, and they will be

surprised to see how little they miss.”* I think he is right in

this, except in supposing that the realists will be surprised.

Many of them already hold the view he is advocating, and others

are very sympathetic to it. At any rate, it is the view which I

shall adopt in these lectures.

 

* Dewey, “Essays in Experimental Logic,” pp. 253, 262.

 

The stuff of the world, so far as we have experience of it,

consists, on the view that I am advocating, of innumerable

transient particulars such as occur in seeing, hearing, etc.,

together with images more or less resembling these, of which I

shall speak shortly. If physics is true, there are, besides the

particulars that we experience, others, probably equally (or

almost equally) transient, which make up that part of the

material world that does not come into the sort of contact with a

living body that is required to turn it into a sensation. But

this topic belongs to the philosophy of physics, and need not

concern us in our present inquiry.

 

Sensations are what is common to the mental and physical worlds;

they may be defined as the intersection of mind and matter. This

is by no means a new view; it is advocated, not only by the

American authors I have mentioned, but by Mach in his Analysis of

Sensations, which was published in 1886. The essence of

sensation, according to the view I am advocating, is its

independence of past experience. It is a core in our actual

experiences, never existing in isolation except possibly in very

young infants. It is not itself knowledge, but it supplies the

data for our knowledge of the physical world, including our own

bodies.

 

There are some who believe that our mental life is built up out

of sensations alone. This may be true; but in any case I think

the only ingredients required in addition to sensations are

images. What images are, and how they are to be defined, we have

now to inquire.

 

The distinction between images and sensations might seem at first

sight by no means difficult. When we shut our eyes and call up

pictures of familiar scenes, we usually have no difficulty, so

long as we remain awake, in discriminating between what we are

imagining and what is really seen. If we imagine some piece of

music that we know, we can go through it in our mind from

beginning to end without any discoverable tendency to suppose

that we are really hearing it. But although such cases are so

clear that no confusion seems possible, there are many others

that are far more difficult, and the definition of images is by

no means an easy problem.

 

To begin with: we do not always know whether what we are

experiencing is a sensation or an image. The things we see in

dreams when our eyes are shut must count as images, yet while we

are dreaming they seem like sensations. Hallucinations often

begin as persistent images, and only gradually acquire that

influence over belief that makes the patient regard them as

sensations. When we are listening for a faint sound—the striking

of a distant clock, or a horse’s hoofs on the road—we think we

hear it many times before we really do, because expectation

brings us the image, and we mistake it for sensation. The

distinction between images and sensations is, therefore, by no

means always obvious to inspection.*

 

* On the distinction between images and sensation, cf. Semon,

“Die mnemischen Empfindungen,” pp. 19-20.

 

We may consider three different ways in which it has been sought

to distinguish images from sensations, namely:

 

(1) By the less degree of vividness in images;

 

(2) By our absence of belief in their “physical reality”;

 

(3) By the fact that their causes and effects are different from

those of sensations.

 

I believe the third of these to be the only universally

applicable criterion. The other two are applicable in very many

cases, but cannot be used for purposes of definition because they

are liable to exceptions. Nevertheless, they both deserve to be

carefully considered.

 

(1) Hume, who gives the names “impressions” and “ideas” to what

may, for present purposes, be identified with our “sensations”

and “images,” speaks of impressions as “those perceptions which

enter with most force and violence” while he defines ideas as

“the faint images of these (i.e. of impressions) in thinking and

reasoning.” His immediately following observations, however, show

the inadequacy of his criteria of “force” and “faintness.” He

says:

 

“I believe it will not be very necessary to employ many words in

explaining this distinction. Every one of himself will readily

perceive the difference betwixt feeling and thinking. The common

degrees of these are easily distinguished, though it is not

impossible but in particular instances they may very nearly

approach to each other. Thus in sleep, in a fever, in madness, or

in any very violent emotions of soul, our ideas may approach to

our impressions; as, on the other hand, it sometimes happens,

that our impressions are so faint and low that we cannot

distinguish them from our ideas. But notwithstanding this near

resemblance in a few instances, they are in general so very

different, that no one can make a scruple to rank them under

distinct heads, and assign to each a peculiar name to mark the

difference” (“Treatise of Human Nature,” Part I, Section I).

 

I think Hume is right in holding that they should be ranked under

distinct heads, with a peculiar name for each. But by his own

confession in the above passage, his criterion for distinguishing

them is not always adequate. A definition is not sound if it only

applies in cases where the difference is glaring: the essential

purpose of a definition is to provide a mark which is applicable

even in marginal cases—except, of course, when we are dealing

with a conception, like, e.g. baldness, which is one of degree

and has no sharp boundaries. But so far we have seen no reason to

think that the difference between sensations and images is only

one of degree.

 

Professor Stout, in his “Manual of Psychology,” after discussing

various ways of distinguishing sensations and images, arrives at

a view which is a modification of Hume’s. He says (I quote from

the second edition):

 

“Our conclusion is that at bottom the distinction between image

and percept, as respectively faint and vivid states, is based on

a difference of quality. The percept has an aggressiveness which

does not belong to the image. It strikes the mind with varying

degrees of force or liveliness according to the varying intensity

of the stimulus. This degree of force or liveliness is part of

what we ordinarily mean by the intensity of a sensation. But this

constituent of the intensity of sensations is absent in mental

imagery”(p. 419).

 

This view allows for the fact that sensations may reach any

degree of faintness—e.g. in the case of a just visible star or a

just audible sound—without becoming images, and that therefore

mere faintness cannot be the characteristic mark of images. After

explaining the sudden shock of a flash of lightning or a

steam-whistle, Stout says that “no mere image ever does strike

the mind in this manner”(p. 417). But I believe that this

criterion fails in very much the same instances as those in which

Hume’s criterion fails in its original form. Macbeth speaks of—

 

that suggestion Whose horrid image doth unfix my

hair And make my seated heart knock at my ribs Against

the use of nature.

 

The whistle of a steam-engine could hardly have a stronger effect

than this. A very intense emotion will often bring with

it—especially where some future action or some undecided issue

is involved—powerful compelling images which may determine the

whole course of life, sweeping aside all contrary solicitations

to the will by their capacity for exclusively possessing the

mind. And in all cases where images, originally recognized as

such, gradually pass into hallucinations, there must be just that

“force or liveliness” which is supposed to be always absent from

images. The cases of dreams and fever-delirium are as hard to

adjust to Professor Stout’s modified criterion as to Hume’s. I

conclude therefore that the test of liveliness, however

applicable in ordinary instances, cannot be used to define the

differences between sensations and images.

 

(2) We might attempt to distinguish images from sensations by our

absence of belief in the “physical reality” of images. When we

are aware that what we are experiencing is an image, we do not

give it the kind of belief that we should give to a sensation: we

do not think that it has the same power of producing knowledge of

the “external world.” Images are “imaginary”;