Aristotle seems to have been the first of ancient philosophers to write a systematic treatise on psychology. But, rather curiously, in this work on psychology there is no special treatment of memory. A special tract, however, was devoted to the subject.[[9]] This, so far as we know, was the first scientific study of memory; and for this reason, as well as for its intrinsic merits, the tract deserves special attention. But before passing to his doctrine of memory, it is well to notice briefly his theory of sense-perceptions. On occasion of appropriate stimuli movements take place in the sense-organs. These movements, however, are not sense perception. In perception the mind must compare and distinguish disparate sensations; it must unite the sensations presented simultaneously by our double sense organs as of sight and hearing, and it must be conscious of sensation. This work of comparison, of psychic synthesis, and of self-conscious perception is performed by a central sense. The physical basis of this sense is the heart. Through it the mind performs the act of sense perception. The functions now attributed to nervous substance are referred by Aristotle to the pneuma connected with the blood. This is the medium by which the movements arising in the sense organs are transmitted to the heart, and in this pneuma the movements persist long after the external stimuli have ceased to act. Incidentally, it is interesting to note, that according to Aristotle’s psychology, the brain has very little to do with mental activity. To borrow a phrase from Wallace, it serves simply as “a cooling apparatus to counteract the excessive warmth of the heart.” When the movement occasioned in the sense organ by an external stimulus is propagated to the heart,[[10]] it becomes a perception of the soul. Sense perception, then, is an act of the soul by means of a physiological process. In the words of Aristotle it is “a movement of the soul through the body.”[[11]] Now this movement sometimes continues after the stimulus, which was the occasion of it, has ceased to act. The extreme case is the well known phenomenon of a visual after-image. The images of the imagination are such after-sensations. Imagination is weak sensation, or in the words of Hobbes, “decaying sense”. So too, dreaming is the result of a movement in our bodily organs, caused either from without or from within. Again, these persisting movements are the elements of memory.
At first, one wonders how Aristotle will distinguish those movements which constitute memory from those which are the basis of imagination. He is not entirely satisfactory on this point; but he makes the following distinction. The picture of the imagination, or the corresponding movement does not refer to an external object, and is not located in the past. The memory picture, on the other hand, does refer to an object and carries with it the consciousness of a time in the past, when the perception remembered took place.[[12]] Memory, then, involves time, and both this and the sense of time are dependent upon the central sense. Memory, as we have seen, is dependent upon the residua of sensations. The subjective side of a sensation is an image. Thus memory belongs to the same part of the soul as the imagination, and the proper objects of memory are images (φανταστὰ). The image is a condition (πάθος) of the central sense. Memory per se is of the original image or perception, and only in an accidental manner does it relate to matters of thought.[[13]]
In his special tract on memory, Aristotle in part repeats Plato’s views, in part discusses the obvious facts of memory, which, having been continually repeated since his time, have become mere platitudes, and in part he tries to explain the phenomena of memory in accordance with his general system of psychology. The essay, however, is of special interest, because in it Aristotle sets forth very clearly the famous doctrine of association of ideas. Some of the other points in the treatise may be briefly mentioned and special consideration given to the portion relating to recollection and association. ¶ First Aristotle takes considerable space to show what would seem to be apparent enough to everybody, that memory is of the past, as perception is of the present, and hope and opinion of the future.
The central sense or sensorium must be in a condition suitable to receive and retain impressions. If the sensorium is too hard, no impression is made. If it is greatly agitated, the new movement is ineffectual: on somewhat the same principle, one may suppose, as one say in modern psychology, that a weak stimulus is washed out by a strong one. Hence the very young and the very old have poor memories; for the former are in the movement of growth, the latter in that of decay. Again, the question arises: How is it that in recollection we recognize the memory image as a picture of the absent object? A scholastic answer is given. “An animal painted in a picture, he says, is both an animal and a copy, and while being thus one and the same, it is nevertheless two things at once. The animal and the copy are not identical, and we may think of the picture either as animal or as a representation. This is also true of the image within us; and the idea which the mind contemplates is something, although it is also the image of something else.”[[14]]
The second chapter of the treatise on memory is devoted chiefly to recollection and the association of ideas. Aristotle distinguishes carefully between the mere persistence and reproduction of a presentation (μνήμη) from voluntary recollection (ἀνάμνησις). The latter is indirect reproduction. It is possible only by the association of ideas. The former is an attribute of animals, while the latter is peculiar to man. Recollection occurs according to the sequence of ideas.[[15]] What and how necessary the sequence shall be depends upon our past experience. “If the sequence be necessary”, Aristotle continues, “then, when this movement occurs, that one will follow. If it is not necessary, but a matter of habit, the latter movement will generally follow.” Sir Wm. Hamilton understands the word translated movement (κίνησις) to mean merely change in quality. The word, then, he thinks may be fairly translated into modern nomenclature by his famous term modification. One hesitates to criticise such a profound scholar and such a diligent student of Aristotle as Sir Wm. Hamilton; but in the light of what has been said it seems much simpler and more in accordance with the psychology of Aristotle to understand his doctrine of recollection as follows: The physiological movements originally connected with a series of perceptions must occur again in the same order when we recall a true memory-picture.[[16]] Man is so constituted that when one movement and the mental image connected with it occur, another movement with its appropriate mental image is likely to follow. When we would recall anything, therefore, we must call up idea after idea until we arrive at one upon which the one we are in search of has often been sequent in our experience. Or in terms of physiology, movement after movement must recur until we arrive at a movement upon which the movement corresponding to the idea desired has often been sequent.
This sequence or association of ideas is subject to certain laws. The remarkable passage in which Aristotle states these laws is translated by Sir Wm. Hamilton as follows:
“When, therefore, we accomplish an act of Reminiscence we pass through a certain series of precursive movements until we arrive at a movement, on which the one we are in quest of is habitually consequent. Hence, too, it is that we hunt through the mental train, excogitating [what we seek] from [its concomitant in] the present, or some other time and from its Similar or Contrary or Coadjacent. Through this process Reminiscence is effected. For the movements, [which and by which we recollect] are, in these cases, and sometimes the same, sometimes at the same time, sometimes parts of the same whole: so that [having obtained from one or the other of these a commencement], the subsequent movement is already more than half accomplished.”[[17]]
Wallace quotes the same passage in the introduction to his Psychology of Aristotle,[[18]] and gives the following somewhat different and probably more accurate translation:—
“When engaged in recollection we seek to excite some of our previous movements until we come to that which the movement or impression of which we are in search was wont to follow. And hence we seek to reach this preceding impression by starting in our thought from an object present to us or something else whether it be similar, contrary, or contiguous to that of which we are in search; recollection taking place in this manner because the movements are in one case identical, in another case coincident and in the last case partly overlap.”[[19]]
Whichever translation we adopt it seems plain enough that Aristotle maintained that voluntary recollection depended upon the laws of association by similarity, contrast or contrariety, and contiguity. Very likely he meant to include simultaneity and sequence; but any proof of this should rest upon the general import of the passage rather than upon any doubtful emendation like Hamilton’s.[[20]]