Philosophical Studies

by G. E. Moore

(3) We may now, therefore, raise the question: Do sensibles ever exist at times when they are not being experienced at all?

To this question it is usual to give a negative answer, and two different a priori reasons may be urged in favour of that answer.

The first is what should be meant by Berkeley's dictum that the esse of sensibles is percipi. This should mean, whatever else it may mean, at least this: that to suppose a sensible to exist and yet not to be experienced in self-contradictory. And this at least seems to me to be clearly false. Anything which was a patch of colour would be a sensible; and to suppose that there are patches of colour which are not being experienced is clearly not self-contradictory, however false it may be.

It may, however, be urged (and this is the second argument) that, though to suppose a thing to be a sensible and yet not experienced is not self-contradictory, yet we can clearly see that nothing can have the one property without having the other. And I do not see my way to deny that we may be able to know, a priori that such a connection holds between two such properties. In the present case, however, I cannot see that it does hold, and therefore, so far as a priori reasons go, I conclude that there is no reason why sensibles should not exist at times when they are not experienced.

It may, however, be asked: Is there any reason to suppose that they ever do? And the reason, which weighs with me most, is one which applies, I think, to a certain class of sensibles only; a class which I will try to define by saying that it consists of those which would (under certain conditions which actually exist) be experienced in a sensation proper, if only a living body, having a certain constitution, existed under those conditions in a position in which no such body does actually exist. I think it is very probable that this definition does not define at all accurately the kind of sensibles I mean; but I think that what the definition aims at will become clearer when I proceed to give my reasons for supposing that sensibles, of a kind to be defined in some such way, do exist unexperienced. The reason is simply that, in Hume's phrase, I have "a strong propensity to believe" that, e.g., the visual sensibles which I directly apprehend in looking at this paper, still exist unchanged when I merely alter the position of my body by turning away my head or closing my eyes, provided that the physical conditions outside my body remain unchanged. In such a case it is certainly true in some sense that I should see sensibles like what I saw the moment before, if only my head were still in the position it was at that moment or my eyes unclosed. But if, in such a case, there is reason to think that sensibles which I should see, if the position of my body were altered, exist in spite of the fact that I do not experience them, there is, I think, an equal reason to suppose it in other cases. We must, for instance, suppose that the sensibles which I should see now, if I were at the other end of the room, or if I were looking under the table, exist at this moment, though they are not being experienced. And similarly we must suppose that the sensibles which you would see, if you were in the position in which I am now, exist at this moment, in spite of the fact that they may be more or less different from those which I see, owing to the different constitution of our bodies. All this implies of course, that a vast number of sensibles exist at any moment, which are not being experienced at all. But still it implies this only with regard to sensibles of a strictly limited class, namely sensibles which would be experienced in a sensation proper, if a body, having a certain constitution, were in a position in which it is not, under the given physical conditions. It does not, for instance, imply that any images, of which it may be true that I should have them, under present physical conditions, if the position of my body were altered, exist now; nor does it imply that sensibles which would be experienced by me now in a sensation proper, if the physical conditions external to my body were different from what they are, exist now.

I feel, of course, that I have only succeeded in defining miserably vaguely the kind of sensibles I mean; and I do not know whether the fact that I have a strong propensity to believe that sensibles of a kind to be defined in some such way, do exist unexperienced, is any good reason for supposing that they actually do. The belief may, of course, be a mere prejudice. But I do not know of any certain test by which prejudices can be distinguished from reasonable beliefs. And I cannot help thinking that there may be a class of sensibles, capable of definition in some such way, which there really is reason to think exist unexperienced.

But, if I am not mistaken, there is an empirical argument which, though, even if it were sound, it would have no tendency whatever to show that no sensibles exist unexperienced, would, if it were sound, show that this very class of sensibles, to which alone my argument for unexperienced existence applies, certainly do not so exist. This, it seems to me, is the most weighty argument which can be used upon the subject; and I want, therefore, to give my reasons for thinking that it is fallacious.

The argument is one which asserts that there is abundant empirical evidence in favour of the view that the existence of the sensibles which we experience at any time, always depends upon the condition of our nervous system: so that, even where it also depends upon external physical conditions, we can safely say that sensibles, which we should have experienced, if only our nervous system had been in a different condition, certainly do not exist, when it is not in that condition. And the fallacy of this argument seems to me to lie in the fact that it does not distinguish between the existence of the sensibles which we experience and the fact that we experience them. What there is evidence for is that our experience of sensibles always depends upon the condition of our nervous system; that, according as the condition of the nervous system changes, different sensibles are experienced, even where other conditions are the same. But obviously the fact that our experience of a given sensible depends upon the condition of our nervous system does not directly show that the existence of the sensible experienced always also so depends. The fact that I am now experiencing this black mark is certainly a different fact from the fact that this black mark now exists. And hence the evidence which does tend to show that the former fact would not have existed if my nervous system had been in a different condition, has no tendency to show that the latter would not have done so either. I am sure that this distinction ought to be made; and hence, though I think there may be other reasons for thinking that the very existence of the sensibles, which we experience, and not merely the fact that we experience them does always depend upon the condition of our nervous systems, it seems to me certain that this particular argument constitutes no such reason.

And I think that those who suppose that it does are apt to be influenced by an assumption, for which also, so far as I can see, there is no reason. I have admitted that the only reason I can see for supposing that sensibles which we experience ever exist unexperienced, seems to lead to the conclusion that the sensibles which would be seen by a colour-blind man, if he occupied exactly the position which I, who am not colour-blind, now occupy, exist now, just as much as those which I now see. And it may be thought that this implies that the sensibles, which he would see, and which would certainly be very different from those which I see, are nevertheless at this moment in exactly the same place as those which I see. Now, for my part, I am not prepared to admit that it is impossible they should be in the same place. But the assumption against which I wish to protest, is the assumption that, if they exist at all, they must be in the same place. I can see no reason whatever for this assumption. And hence any difficulties there may be in the way of supposing that they could be in the same place at the same time as the sensibles which I see, do not at all apply to my hypothesis, which is only that they exist now, not that they exist in the same place in which mine do.

On this question, therefore, as to whether sensibles ever exist at times when they are not experienced, I have only to say (1) that I think there is certainly no good reason whatever for asserting that no sensibles do; and (2) that I think perhaps a certain amount of weight ought to be attached to our instinctive belief that certain kinds of sensibles do; and that here again any special arguments which may be brought forward to show that, whether some sensibles exist unexperienced or not, this kind certainly do not, are, so far as I can see, wholly inconclusive.