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