"Manifestly," he replies, "we must believe that the impression which is produced, in consequence of the sensation, in the soul, and in that part of the body which perceives the sensation, is analogous to a species of painting, and that the perception of that impression constitutes precisely what we call memory. The movement which then takes place in the mind imprints there a sort of type of the sensation analogous to the seal which one imprints on wax with a ring. Hence it is that those who by the violence of the impression, or by the ardor of age are in a great excitement (movement) have not the memory of things, as if the movement and seal had been applied to running water. In the case of others, however, who are in a sort cold, as the plaster of old edifices, the very hardness of the part which receives the impression prevents the image from leaving the least trace. Hence it is that young children and old men have so little memory. It is the same with those who are too lively, and those who are too slow. Neither remember well. The one class are too humid, the other too hard. The image dwells not in the soul of the one, makes no impression whatever on that of the other.
"How is it now," he goes on to ask, "that this stamp, impression, image, or painting, in us, a mere mode of the mind, can recall the absent object?" His answer is, that the impression or image is a copy of that object, while, at the same time, it is, in itself considered, only a modification of our mind, just as a painting is a mere picture, and yet a copy from nature. (Parva Naturalia: Memory, ch. 1.)
Defence of Aristotle.—Sir W. Hamilton defends Aristotle against the strictures of Dr. Reid, upon this subject, by the supposition that he used these expressions not in a literal, but in a figurative or analogical sense. The figure, however, if it be one, is very clearly and boldly sustained, and constitutes, in fact, the whole explanation given of the process of memory—the entire theory. Take away these expressions, and you take away the whole substance of his argument, the whole solution of the problem. Sensation, or intellectual conception, produces an impression on the soul, and imprints there a type of itself, not unlike a painting or the stamp of a seal on wax, and the perception of this is memory. Such is in brief his theory.
Theory of Hobbes.—Not far remote from this was the theory of Hobbes, who regarded memory as a decaying or vanishing sense; that of Hume, who represents it as merely a somewhat weaker impression than that which we designate as perception; and that of the celebrated Malebranche, who accounted for memory by making it to depend entirely on the changes which take place in the fibres of the brain. "For even as the branches of a tree which have continued some time bent in a certain form, still preserve an aptitude to be bent anew after the same manner, so the fibres of the brain having once received certain impressions by the course of the animal spirits, and by the action of objects, retain a long time some facility to receive these same dispositions. Now the memory consists only in this faculty, since we think on the same things when the brain receives the same impressions."
He goes on to explain how, as the brain undergoes a change in different periods of life, the mind is affected accordingly. "The fibres of the brain in children are soft, flexible, and delicate; a riper age dries, hardens, and strengthens them; but in old age they become wholly inflexible." ... "For as we see the fibres which compose the flesh harden by time, and that the flesh of a young partridge is, without dispute, more tender than that of an old one, so the fibres of the brain of a child or youth will be much more soft and delicate than those of persons more advanced in years."
Strictures upon this Theory.—Without disputing what is here stated as to the difference in the fibres of the brain at different periods of life, it remains to be proved that all this has any thing to do with the differences of memory in different persons, or with the phenomena of memory in general.
These theories, it will be observed, all assume that in perception and sensation some physical effect is produced on the system, which remains after the original sensation or perception has ceased to act, and that memory is the result of that remaining effect, the perception, or conscious cognizance of it by the mind. The process is a purely physiological one. Without insisting on the expressions made use of to represent this process, all which convey the idea strongly of a mechanical effect—type imprinted on the soul, impression made on it as of a seal on wax, image, picture, copy, etc.; allowing these to be mere metaphors; allowing, moreover, that the essential fact all along assumed, is a fact, viz., that in sensation, perception, etc., some physical effect is produced on the sensorium; there are still two essential propositions to be established before we can admit any of these theories: 1. That this physical effect remains any time after the cause ceases to operate; 2. That if so, it is in any way concerned in the production of memory; and even if these points could be made out, it would still be an open question, in WHAT way, possible or conceivable, this effect or impression on the sensorium gives rise to the phenomenon of memory; for this is, after all, the chief thing to be explained.