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 W^m. 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 W^m. 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 W^m. 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]