The Problems of Philosophy by Bertrand Russel - HTML preview

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The existence of matter

In this chapter we have to ask ourselves whether, in any sense at all,

there is such a thing as matter. Is there a table which has a certain intrinsic nature, and continues to exist when I am not looking, or is the table

merely a product of my imagination, a dream-table in a very prolonged

dream? This question is of the greatest importance. For if we cannot be

sure of the independent existence of objects, we cannot be sure of the in-

dependent existence of other people’s bodies, and therefore still less of

other people’s minds, since we have no grounds for believing in their

minds except such as are derived from observing their bodies. Thus if we

cannot be sure of the independent existence of objects, we shall be left

alone in a desert—it may be that the whole outer world is nothing but a

dream, and that we alone exist. This is an uncomfortable possibility; but

although it cannot be strictly proved to be false, there is not the slightest reason to suppose that it is true. In this chapter we have to see why this is the case.

Before we embark upon doubtful matters, let us try to find some more

or less fixed point from which to start. Although we are doubting the

physical existence of the table, we are not doubting the existence of the

sense-data which made us think there was a table; we are not doubting

that, while we look, a certain colour and shape appear to us, and while

we press, a certain sensation of hardness is experienced by us. All this,

which is psychological, we are not calling in question. In fact, whatever

else may be doubtful, some at least of our immediate experiences seem

absolutely certain.

Descartes (1596-1650), the founder of modern philosophy, invented a

method which may still be used with profit—the method of systematic

doubt. He determined that he would believe nothing which he did not

see quite clearly and distinctly to be true. Whatever he could bring him-

self to doubt, he would doubt, until he saw reason for not doubting it. By applying this method he gradually became convinced that the only


existence of which he could be quite certain was his own. He imagined a deceitful demon, who presented unreal things to his senses in a perpetu-al phantasmagoria; it might be very improbable that such a demon exis-

ted, but still it was possible, and therefore doubt concerning things per-

ceived by the senses was possible.

But doubt concerning his own existence was not possible, for if he did

not exist, no demon could deceive him. If he doubted, he must exist; if he had any experiences whatever, he must exist. Thus his own existence

was an absolute certainty to him. ‘I think, therefore I am,’ he said ( Cogito, ergo sum); and on the basis of this certainty he set to work to build up again the world of knowledge which his doubt had laid in ruins. By inventing the method of doubt, and by showing that subjective things are

the most certain, Descartes performed a great service to philosophy, and

one which makes him still useful to all students of the subject.

But some care is needed in using Descartes’ argument. ‘I think, there-

fore I am’ says rather more than is strictly certain. It might seem as

though we were quite sure of being the same person to-day as we were

yesterday, and this is no doubt true in some sense. But the real Self is as hard to arrive at as the real table, and does not seem to have that absolute, convincing certainty that belongs to particular experiences. When I

look at my table and see a certain brown colour, what is quite certain at

once is not ‘ I am seeing a brown colour’, but rather, ‘a brown colour is being seen’. This of course involves something (or somebody) which (or

who) sees the brown colour; but it does not of itself involve that more or less permanent person whom we call ‘I’. So far as immediate certainty

goes, it might be that the something which sees the brown colour is quite

momentary, and not the same as the something which has some different

experience the next moment.

Thus it is our particular thoughts and feelings that have primitive cer-

tainty. And this applies to dreams and hallucinations as well as to nor-

mal perceptions: when we dream or see a ghost, we certainly do have the

sensations we think we have, but for various reasons it is held that no

physical object corresponds to these sensations. Thus the certainty of our knowledge of our own experiences does not have to be limited in any

way to allow for exceptional cases. Here, therefore, we have, for what it

is worth, a solid basis from which to begin our pursuit of knowledge.

The problem we have to consider is this: Granted that we are certain of

our own sense-data, have we any reason for regarding them as signs of

the existence of something else, which we can call the physical object?

When we have enumerated all the sense-data which we should naturally


regard as connected with the table, have we said all there is to say about the table, or is there still something else—something not a sense-datum,

something which persists when we go out of the room? Common sense

unhesitatingly answers that there is. What can be bought and sold and

pushed about and have a cloth laid on it, and so on, cannot be a mere collection of sense-data. If the cloth completely hides the table, we shall derive no sense-data from the table, and therefore, if the table were merely sense-data, it would have ceased to exist, and the cloth would be suspen-ded in empty air, resting, by a miracle, in the place where the table

formerly was. This seems plainly absurd; but whoever wishes to become

a philosopher must learn not to be frightened by absurdities.

One great reason why it is felt that we must secure a physical object in

addition to the sense-data, is that we want the same object for different

people. When ten people are sitting round a dinner-table, it seems pre-

posterous to maintain that they are not seeing the same tablecloth, the

same knives and forks and spoons and glasses. But the sense-data are

private to each separate person; what is immediately present to the sight

of one is not immediately present to the sight of another: they all see

things from slightly different points of view, and therefore see them

slightly differently. Thus, if there are to be public neutral objects, which can be in some sense known to many different people, there must be

something over and above the private and particular sense-data which

appear to various people. What reason, then, have we for believing that

there are such public neutral objects?

The first answer that naturally occurs to one is that, although different

people may see the table slightly differently, still they all see more or less similar things when they look at the table, and the variations in what

they see follow the laws of perspective and reflection of light, so that it is easy to arrive at a permanent object underlying all the different people’s sense-data. I bought my table from the former occupant of my room; I

could not buy his sense-data, which died when he went away, but I could and did buy the confident expectation of more or less similar

sense-data. Thus it is the fact that different people have similar sense-

data, and that one person in a given place at different times has similar

sense-data, which makes us suppose that over and above the sense-data

there is a permanent public object which underlies or causes the sense-

data of various people at various times.

Now in so far as the above considerations depend upon supposing

that there are other people besides ourselves, they beg the very question

at issue. Other people are represented to me by certain sense-data, such


as the sight of them or the sound of their voices, and if I had no reason to believe that there were physical objects independent of my sense-data, I

should have no reason to believe that other people exist except as part of my dream. Thus, when we are trying to show that there must be objects

independent of our own sense-data, we cannot appeal to the testimony

of other people, since this testimony itself consists of sense-data, and

does not reveal other people’s experiences unless our own sense-data are

signs of things existing independently of us. We must therefore, if pos-

sible, find, in our own purely private experiences, characteristics which

show, or tend to show, that there are in the world things other than

ourselves and our private experiences.

In one sense it must be admitted that we can never prove the existence

of things other than ourselves and our experiences. No logical absurdity

results from the hypothesis that the world consists of myself and my

thoughts and feelings and sensations, and that everything else is mere

fancy. In dreams a very complicated world may seem to be present, and

yet on waking we find it was a delusion; that is to say, we find that the

sense-data in the dream do not appear to have corresponded with such

physical objects as we should naturally infer from our sense-data. (It is

true that, when the physical world is assumed, it is possible to find physical causes for the sense-data in dreams: a door banging, for instance,

may cause us to dream of a naval engagement. But although, in this case,

there is a physical cause for the sense-data, there is not a physical object corresponding to the sense-data in the way in which an actual naval

battle would correspond.) There is no logical impossibility in the suppos-

ition that the whole of life is a dream, in which we ourselves create all

the objects that come before us. But although this is not logically im-

possible, there is no reason whatever to suppose that it is true; and it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life, than the common-sense hypothesis that there really

are objects independent of us, whose action on us causes our sensations.

The way in which simplicity comes in from supposing that there really

are physical objects is easily seen. If the cat appears at one moment in

one part of the room, and at another in another part, it is natural to suppose that it has moved from the one to the other, passing over a series of intermediate positions. But if it is merely a set of sense-data, it cannot have ever been in any place where I did not see it; thus we shall have to

suppose that it did not exist at all while I was not looking, but suddenly sprang into being in a new place. If the cat exists whether I see it or not, we can understand from our own experience how it gets hungry


between one meal and the next; but if it does not exist when I am not see-

ing it, it seems odd that appetite should grow during non-existence as

fast as during existence. And if the cat consists only of sense-data, it cannot be hungry, since no hunger but my own can be a sense-datum to me.

Thus the behaviour of the sense-data which represent the cat to me,

though it seems quite natural when regarded as an expression of hunger,

becomes utterly inexplicable when regarded as mere movements and

changes of patches of colour, which are as incapable of hunger as a tri-

angle is of playing football.

But the difficulty in the case of the cat is nothing compared to the difficulty in the case of human beings. When human beings speak—that is,

when we hear certain noises which we associate with ideas, and simul-

taneously see certain motions of lips and expressions of face—it is very

difficult to suppose that what we hear is not the expression of a thought, as we know it would be if we emitted the same sounds. Of course similar

things happen in dreams, where we are mistaken as to the existence of

other people. But dreams are more or less suggested by what we call

waking life, and are capable of being more or less accounted for on sci-

entific principles if we assume that there really is a physical world. Thus every principle of simplicity urges us to adopt the natural view, that

there really are objects other than ourselves and our sense-data which

have an existence not dependent upon our perceiving them.

Of course it is not by argument that we originally come by our belief in

an independent external world. We find this belief ready in ourselves as

soon as we begin to reflect: it is what may be called an instinctive belief.

We should never have been led to question this belief but for the fact

that, at any rate in the case of sight, it seems as if the sense-datum itself were instinctively believed to be the independent object, whereas argument shows that the object cannot be identical with the sense-datum.

This discovery, however—which is not at all paradoxical in the case of

taste and smell and sound, and only slightly so in the case of

touch—leaves undiminished our instinctive belief that there are objects corresponding to our sense-data. Since this belief does not lead to any difficulties, but on the contrary tends to simplify and systematize our ac-

count of our experiences, there seems no good reason for rejecting it. We

may therefore admit—though with a slight doubt derived from

dreams—that the external world does really exist, and is not wholly de-

pendent for its existence upon our continuing to perceive it.

The argument which has led us to this conclusion is doubtless less

strong than we could wish, but it is typical of many philosophical


arguments, and it is therefore worth while to consider briefly its general character and validity. All knowledge, we find, must be built up upon

our instinctive beliefs, and if these are rejected, nothing is left. But among our instinctive beliefs some are much stronger than others, while many

have, by habit and association, become entangled with other beliefs, not

really instinctive, but falsely supposed to be part of what is believed


Philosophy should show us the hierarchy of our instinctive beliefs, be-

ginning with those we hold most strongly, and presenting each as much

isolated and as free from irrelevant additions as possible. It should take care to show that, in the form in which they are finally set forth, our instinctive beliefs do not clash, but form a harmonious system. There can

never be any reason for rejecting one instinctive belief except that it

clashes with others; thus, if they are found to harmonize, the whole sys-

tem becomes worthy of acceptance.

It is of course possible that all or any of our beliefs may be mistaken, and therefore all ought to be held with at least some slight element of

doubt. But we cannot have reason to reject a belief except on the ground of some other belief. Hence, by organizing our instinctive beliefs and

their consequences, by considering which among them is most possible,

if necessary, to modify or abandon, we can arrive, on the basis of accept-

ing as our sole data what we instinctively believe, at an orderly system-

atic organization of our knowledge, in which, though the possibility of error remains, its likelihood is diminished by the interrelation of the parts and by the critical scrutiny which has preceded acquiescence.

This function, at least, philosophy can perform. Most philosophers,

rightly or wrongly, believe that philosophy can do much more than

this—that it can give us knowledge, not otherwise attainable, concerning

the universe as a whole, and concerning the nature of ultimate reality.

Whether this be the case or not, the more modest function we have

spoken of can certainly be performed by philosophy, and certainly suf-

fices, for those who have once begun to doubt the adequacy of common

sense, to justify the arduous and difficult labours that philosophical

problems involve.