(II)

I now pass to the question how sensibles are related to physical objects. And here I want to say, to begin with, that I feel extremely puzzled about the whole subject. I find it extremely difficult to distinguish clearly from one another the different considerations which ought to be distinguished; and all I can do is to raise, more or less vaguely, certain questions as to how certain particular sensibles are related to certain particular physical objects, and to give the reasons which seem to me to have most weight for answering these questions in one way rather than another. I feel that all that I can say is very tentative.

To begin with, I do not know how “physical object” is to be defined, and I shall not try to define it. I shall, instead, consider certain propositions, which everybody will admit to be propositions about physical objects, and which I shall assume that I know to be true. And the question I shall raise is as to how these propositions are to be interpreted—in what sense they are true; in considering which, we shall at the same time consider how they are related to certain sensibles.

I am looking at two coins, one of which is a half-crown, the other a florin. Both are lying on the ground; and they are situated obliquely to my line of sight, so that the visual sensibles which I directly apprehend in looking at them are visibly elliptical, and not even approximately circular. Moreover, the half-crown is so much farther from me than the florin that its visual sensible is visibly smaller than that of the florin.

In these circumstances I am going to assume that I know the following propositions to be true; and no one, I think, will deny that we can know such propositions to be true, though, as we shall see, extremely different views may be taken as to what they mean. I know (a) that, in the ordinary sense of the word “see” I am really seeing two coins; an assertion which includes, if it is not identical with, the assertion that the visual experiences, which consist in my direct apprehension of those two elliptical patches of colour, are sensations proper, and are not either hallucinations nor mere experiences of “images”; (b) that the upper sides of the coins are really approximately circular, and not merely elliptical like the visual sensibles; that the coins have another side, and an inside, though I don’t see it; (d) that the upper side of the half-crown is really larger than that of the florin, though its visual sensible is smaller than the visual sensible of the upper side of the florin: (e) that both coins continue to exist, even when I turn away my head or shut my eyes; but in saying this, I do not, of course, mean to say that there is absolutely no change in them; I daresay there must be some change, and I do not know how to define exactly what I do mean. But we can, I think, say at least this: viz., that propositions (b), (c), and (d) will still be true, although proposition (a) has ceased to be true.

Now all these propositions are, I think, typical propositions of the sort which we call propositions about physical objects; and the two coins themselves are physical objects, if anything is. My question is: In what sense are these propositions true?

And in considering this question, there are, I think, two principles which we can lay down as certain to begin with; though they do not carry us very far.

The one is (a) that the upper side of the coin, which I am said to see, is not simply identical with the visual sensible which I directly apprehend in seeing it. That this is so might be thought to follow absolutely from each of the two facts which I have called (b) and (d); but I am not quite sure that it does follow from either of these or from both together: for it seems to me just possible that the two sensibles in question, though not circular in my private space, may yet be circular in physical space; and similarly that though the sensible of the half-crown is smaller than that of the florin in my private space, it may be larger in physical space. But what I think it does follow from is the fact that another person may be seeing the upper side of the coin in exactly the same sense in which I am seeing it, and yet his sensible be certainly different from mine. From this it follows absolutely that the upper side of the coin cannot be identical with both sensibles, since they are not identical with one another. And though it does not follow absolutely that it may not be identical with one of the two, yet it does follow that we can get a case in which it is not identical with mine and I need only assume that the case I am taking is such a case.

From this it follows that we must distinguish that sense of the word “see” in which we can be said to “see” a physical object, from that sense of the word in which “see” means merely to directly apprehend a visual sensible. In a proposition of the form “I see A,’’ where A is a name or description of some physical object, though, if this proposition is to be true, there must be some visual sensible, B, which I am directly apprehending, yet the proposition “I see A” is certainly not always, and probably never, identical in meaning with the proposition “I directly apprehend B.” In asserting “I see A” we are asserting not only that we directly apprehend some sensible but also something else about this sensible—it may be only some proposition of the form, “and this sensible has certain other properties,” or it may be some proposition of the form “and I know this sensible to have certain other properties.” Indeed we have not only to distinguish that sense of the word “perceive” in which it is equivalent to “directly apprehend,” from one sense in which we can be said to perceive a physical object; we have also to distinguish at least two different senses in which we can be said to perceive physical objects, different both from one another and from “directly apprehend.” For it is obvious that though I should be said to be now seeing the half-crown, there is a narrower, and more proper, sense, in which I can only be said to see one side of it—not its lower side or its inside, and not therefore the whole half-crown.

The other principle, which we can lay down to start with is (β) that my knowledge of all the five propositions (a) to (e), is based, in the last resort, on experiences of mine consisting in the direct apprehension of sensibles and in the perception of relations between directly apprehended sensibles. It is based on these, in at least this sense, that I should never have known any of these propositions if I had never directly apprehended any sensibles nor perceived any relations between them.

What, in view of these two principles, can be the sense in which my five propositions are true?

(1) It seems to me possible that the only true interpretation which can be given to any of them is an interpretation of a kind which I can only indicate rather vaguely as follows: Namely, that all of them express only a kind of fact which we should naturally express by saying that, if certain conditions were fulfilled, I or some other person, should directly apprehend certain other sensibles. For instance the only true thing that can be meant by saying that I really see coins may be some such thing as that, if I were to move my body in certain ways, I should directly apprehend other sensibles, e.g. tactual ones, which I should not directly apprehend as a consequence of these movements, if these present visual experiences of mine were mere hallucinations or experiences of “images.” Again, the only true thing that can be meant by saying that the upper sides of the coins are really approximately circular may be some such thing as that, if I were looking straight at them, I should directly apprehend circular sensibles. And similarly, the only true interpretation of (c) may be some such fact as that, if I were to turn the coins over, or break them up, I should have certain sensations, of a sort I can imagine very well; of (d) that if I were at an equal distance from the half-crown and the florin, the sensible, I should then see corresponding to the half-crown would be bigger than that corresponding to the florin, whereas it is now smaller; of (e) that, if, when my eyes were closed, they had been open instead, I should have seen certain sensibles.

It is obvious, indeed, that if any interpretation on these lines is the only true interpretation of our five propositions, none of those which I have vaguely suggested comes anywhere near to expressing it in its ultimate form. They cannot do so for the simple reason that, in them, the conditions under which I should experience certain other sensibles are themselves expressed in terms of physical objects, and not in terms of sensibles and our experience of them. The conditions are expressed in such terms as “if I were to move my body,” “if I were to look straight at the coins,” “if I were to turn the coins over,” etc.; and all these are obviously propositions, which must themselves again be interpreted in terms of sensibles, if our original five propositions need to be so. It is obvious, therefore, that any ultimate interpretation of our five propositions, on these lines, would be immensely complicated; and I cannot come anywhere near to stating exactly what it would be. But it seems to me possible that some such interpretation could be found, and that it is the only true one.

The great recommendation of this view seems to me to be that it enables us to see, more clearly than any other view can, how our knowledge of physical propositions can be based on our experience of sensibles, in the way in which principle (β) asserts it to be. If, when I know that the coins are round, all that I know is some such thing as that if, after experiencing the sensibles I do now experience, I were to experience still others, I should finally experience a third set, we can understand, as clearly as we can understand how any knowledge can be obtained by induction at all, how such a knowledge could be based on our previous experience of sensibles, and how it could be verified by our subsequent experience.

On the other hand, apart from the difficulty of actually giving any interpretation on these lines, which will meet the requirements, the great objection to it seems to me to be this. It is obvious that, on this view, though we shall still be allowed to say that the coins existed before I saw them, are circular etc., all these expressions, if they are to be true, will have to be understood in a Pickwickian sense. When I know that the coins existed before I saw them, what I know will not be that anything whatever existed at that time, in the sense in which those elliptical patches of colour exist now. All that I know will be simply that, since the elliptical patches exist now, it is true, that, if certain unrealised conditions had been realised, I should have had certain sensations that I have not had; or, if certain conditions, which may or may not be realised in the future, were to be so, I should have certain experiences. Something like this will actually be the only true thing that can be meant by saying that the coins existed before I saw them. In other words, to say of a physical object that it existed at a given time will always consist merely in saying of some sensible, not that it existed at the time in question, but something quite different and immensely complicated. And thus, though, when I know that the coins exist, what I know will be merely some proposition about these sensibles which I am directly apprehending, yet this view will not contradict principle (α) by identifying the coins with the sensibles. For it will say that to assert a given thing of the coins is not equivalent to asserting the same thing of the sensibles, but only to asserting of them something quite different.

The fact that these assertions that the coins exist, are round, etc., will, on this view, only be true in this outrageously Pickwickian sense, seems to me to constitute the great objection to it. But it seems to me to be an objection only, so far as I can see, because I have a “strong propensity to believe” that, when I know that the coins existed before I saw them, what I know is that something existed at that time, in the very same sense in which those elliptical patches now exist. And, of course, this belief may be a mere prejudice. It may be that when I believe that I now have, in my body, blood and nerves and brain, what I believe is only true, if it does not assert, in the proper sense of the word “existence,” the present existence of anything whatever, other than sensibles which I directly apprehend, but only makes assertions as to the kind of experiences a doctor would have, if he dissected me. But I cannot feel at all sure that my belief, that, when I know of the present existence of these things (as I think I do), I am knowing of the present existence (in the proper sense) of things other than any sensibles which I or any one else am now directly apprehending, is a mere prejudice. And therefore I think it is worth while to consider what, if it is not, these things, of whose existence I know, can be.

(2) It is certain that if, when I know that that half-crown existed before I saw it, I am knowing that something existed at that time in other than a Pickwickian sense, I only know this something by description; and it seems pretty clear that the description by which I know it is as the thing which has a certain connection with this sensible which I am now directly apprehending. But what connection? We cannot simply say, as many people have said, that by “that half-crown” I mean the thing which caused my experience of this sensible; because events which happen between the half-crown and my eyes, and events in my eyes, and optic nerves, and brains are just as much causes of my experiences as the half-crown itself. But it may perhaps be the case that the half-crown has some particular kind of causal relation to my experience, which these other events have not got—a kind which may be expressed, perhaps, by saying that it is its “source.” And hence, when I know that that half-crown is circular, I may perhaps be knowing that the source of this experience is circular.

But what sort of a thing can this “source” be?

One kind of view, which I think is very commonly held, is that it is something “spiritual” in its nature, or something whose nature is utterly unknown to us. And those who hold this view are apt to add, that it is not really “circular,” in any sense at all; nor is the “source” of my half-crown experience, in any sense at all, “bigger” than that of my florin experience. But if this addition were seriously meant, it would, of course, amount to saying that propositions (b) and (d) are not true, in any sense at all; and I do not think that those who make it, really mean to say this. I think that what they mean is only that the only sense in which those “sources” are circular, and one bigger than the other, is one in which to say this merely amounts to saying that the sensibles, which they would cause us to experience, under certain conditions, would be circular, and one bigger than the other. In other words, in order to give a true interpretation to the propositions that the coins are circular and one bigger than the other, they say that we must interpret them in the same kind of way in which view interpreted them; and the only difference between their view and view (1), is that, whereas that said that you must give a Pickwickian interpretation both to the assertion that the coins exist, and to the assertion that they are circular, they say that you must not give it to the former assertion, and must to the latter.

To this view my objection is only that any reason there may be for saying that the “sources” exist in other than a Pickwickian sense, seems to me to be also a reason for saying that they are “circular” in a sense that is not Pickwickian. I have just as strong a propensity to believe that they are really circular, in a simple and natural sense, as that they exist in such a sense: and I know of no better reason for believing either.

(3) It may be suggested, next, that these “sources,” instead of being something spiritual in their nature or something of a nature utterly unknown, consist simply of sensibles, of a kind which I have previously tried to define; namely of all those sensibles, which anybody would, under the actual physical conditions, experience in sensations proper of which the half-crown and the florin were the source, if their bodies were in any of the positions relatively to those coins, in which they would get sensations from them at all. We saw before that it seems possible that all these sensibles do really exist at times when they are not experienced, and that some people, at all events, seem to have a strong propensity to believe that they do. And in favour of the view that some such huge collection of sensibles is the upper side of the half-crown, is the fact that we do seem to have a strong propensity to believe that any particular sensible, which we directly apprehend in looking at the upper side of the half-crown, and of our direct apprehension of which the upper side is the source, is in the place in which the upper side is. And that some sense might be given to the expression “in the same place as,” in which it could be true that sensibles of all sorts of different shapes and sizes, and of all sorts of different colours, were in the same place at the same time, seems to me to be possible. But the objection to this view seems to me to be the same as to the last; namely that if the upper side of the half-crown were identical with such a collection of sensibles, then the only sense in which it could be said to be “circular,” or bigger than that of the florin, would certainly be very Pickwickian, though not the same as on that view.

(4) If, for the reasons given, we reject both (1), (2), and (3) as interpretations of our five propositions, the only alternative I can think of that remains, is one which is roughly identical, so far as I can see, with Locke’s view. It is a view which asserts that the half-crown and the florin really did exist (in the natural sense) before I saw them; that they really are approximately circular (again in the natural sense); that, therefore, they are not composed of sensibles which I or others should directly apprehend under other conditions; and that therefore also neither these sensibles (even if such do now exist) nor those which I am now directly apprehending are in the place in which the coins are. It holds, therefore, that the coins do really resemble some sensibles, in respect of the “primary” qualities which these have; that they really are round, and one larger than the other, in much the same sense in which some sensibles are round and some larger than others. But it holds also that no sensibles which we ever do directly apprehend, or should directly apprehend, if at a given time we were in other positions, are parts of those coins; and that, therefore, there is no reason to suppose that any parts of the coins have any of the “secondary qualities” —colour, etc.—which any of these sensibles have.

On this view, it is plain, there is nothing to prevent us from holding that, as suggested in I (3), all sorts of unexperienced sensibles do exist. We are only prevented from holding that, if they do, those which have the same source all exist in the same place as their source. And the natural view to take as to the status of sensibles generally, relatively to physical objects, would be that none of them, whether experienced or not, were ever in the same place as any physical object. That none, therefore, exist “anywhere” in physical space; while, at the same time, we can also say, as argued in I (2), that none exist “in the mind,” except in the sense that some are directly apprehended by some minds. And the only thing that would need to be added, is that some, and some only, resemble the physical objects which are their source, in respect of their shape.

To this view I can see no objection except the serious one that it is difficult to answer the questions: How can I ever come to know that these sensibles have a “source” at all? And how do I know that these “sources” are circular? It would seem that, if I do know these things at all, I must know immediately, in the case of some sensibles, both that they have a source and what the shape of this source is. And to this it may be objected that this is a kind of thing which I certainly cannot know immediately. The argument in favour of an interpretation of type (1) seems to me to rest wholly on the assumption that there are only certain kinds of facts which I can know immediately; and hence that if I believe I know a fact, which is not of this kind, and which also I cannot have learnt immediately, my belief must be a mere prejudice. But I do not know how it can be shown that an assertion of the form: Facts of certain kinds are the only ones you can know immediately; is itself not a prejudice. I do not think, therefore, that the fact that, if this last view were true, we should have to admit that we know immediately facts of a kind which many people think we cannot know immediately, is a conclusive objection to it.