For the understanding of memory, it is a help to consider the links connecting its most developed forms with other occurrences of a less complex kind. True recollection comes at the end of a series of stages. I shall distinguish five stages on the way, so that recollection becomes the sixth in gradual progress. The stages are as follows:
1. Images.—As we have seen, images, at any rate in their simpler parts, in fact copy past sensations more or less vaguely, even when they are not known to do so. Images are “mnemic” phenomena, in the sense that they are called up by stimuli formerly associated with their prototypes, so that their occurrence is a result of past experience according to the law of association. But obviously an image which in fact copies a past occurrence does not constitute a recollection unless it is felt to be a copy.
2. Familiarity.—Images and perceptions may come to us, and so may words or other bodily movements, with more or less of the feeling we call “familiarity”. When you recall a tune that you have heard before, either by images or by actually singing it, part of what comes to you may feel familiar, part unfamiliar. This may lead you to judge that you have remembered the familiar part rightly and the unfamiliar part wrongly, but this judgment belongs to a later stage.
3. Habit-Memory.—We have already discussed this in [Chapter VI]. People say they remember a poem if they can repeat it correctly. But this does not necessarily involve any recollection of a past occurrence; you may have quite forgotten when and where you read the poem. This sort of memory is mere habit, and is essentially like knowing how to walk although you cannot remember learning to walk. This does not deserve to be called memory in the strict sense.
4. Recognition.—This has two forms. (a) When you see a dog, you can say to yourself “there is a dog”, without recalling any case in which you have seen a dog before, and even without reflecting that there have been such cases. This involves no knowledge about the past; essentially it is only an associative habit. (b) You may know “I saw this before”, though you do not know when or where, and cannot recollect the previous occurrence in any way. In such a case there is knowledge about the past, but it is very slight. When you judge: “I saw this before”, the word “this” must be used vaguely, because you did not see exactly what you see now, but only something very like this. Thus all that you are really knowing is that, on some past occasion, you saw something very like what you are seeing now. This is about the minimum of knowledge about the past that actually occurs.
5. Immediate Memory.—I come now to a region intermediate between sensation and true memory, the region of what is sometimes called “immediate memory”. When a sense-organ is stimulated, it does not, on the cessation of the stimulus, return at once to its unstimulated condition: it goes on (so to speak) vibrating, like a piano-string, for a short time. For example, when you see a flash of lightning, your sensation, brief as it is, lasts much longer than the lightning as a physical occurrence. There is a period during which a sensation is fading: it is then called an “acoleuthic” sensation. It is owing to this fact that you can see a movement as a whole. As observed before, you cannot see the minute-hand of a watch moving, but you can see the second-hand moving. That is because it is in several appreciably different places within the short time that is required for one visual sensation to fade, so that you do actually, at one moment, see it in several places. The fading sensations, however, feel different from those that are fresh, and thus the various positions which are all sensibly present are placed in a series by the degree of fading, and you acquire the perception of movement as a process. Exactly the same considerations apply to hearing a spoken sentence.
Thus not only an instant, but a short finite time is sensibly present to you at any moment. This short finite time is called the “specious present”. By the felt degree of fading, you can distinguish earlier and later in the specious present, and thus experience temporal succession without the need of true memory. If you see me quickly move my arm from left to right, you have an experience which is quite different from what you would have if you now saw it at the right and remembered that a little while ago you saw it at the left. The difference is that, in the quick movement, the whole falls within the specious present, so that the entire process is sensible. The knowledge of something as in the immediate past, though still sensible, is called “immediate memory”. It has great importance in connection with our apprehension of temporal processes, but cannot count as a form of true memory.
6. True Recollection.—We will suppose, for the sake of definiteness, that I am remembering what I had for breakfast this morning. There are two questions which we must ask about this occurrence: (a) What is happening now when I recollect? (b) What is the relation of the present happening to the event remembered? As to what is happening now, my recollection may involve either images or words; in the latter case, the words themselves may be merely imagined. I will take the case in which there are images without words, which must be the more primitive, since we cannot suppose that memory would be impossible without words.
The first point is one which seems so obvious that I should be ashamed to mention it, but for the fact that many distinguished philosophers think otherwise. The point is this: whatever may be happening now, the event remembered is not happening. Memory is often spoken of as if it involved the actual persistence of the past which is remembered; Bergson, e.g. speaks of the interpenetration of the present by the past. This is mere mythology; the event which occurs when I remember is quite different from the event remembered. People who are starving can remember their last meal, but the recollection does not appease their hunger. There is no mystic survival of the past when we remember; merely a new event having a certain relation to the old one. What this relation is, we shall consider presently.
It is quite clear that images are not enough to constitute recollection, even when they are accurate copies of a past occurrence. One may, in a dream, live over again a past experience; while one is dreaming, one does not seem to be recalling a previous occurrence, but living through a fresh experience. We cannot be said to be remembering, in the strict sense, unless we have a belief referring to the past. Images which, like those in dreams, feel as if they were sensations, do not constitute recollection. There must be some feeling which makes us refer the images to a past prototype. Perhaps familiarity is enough to cause us to do so. And perhaps this also explains the experience of trying to remember something and feeling that we are not remembering it right. Parts of a complex image may feel more familiar than other parts, and we then feel more confidence in the correctness of the familiar parts than in that of the others. The conviction that the image we are forming of a past event is wrong might seem to imply that we must be knowing the past otherwise than by images, but I do not think this conclusion is really warranted, since degrees of familiarity in images suffice to explain this experience.