The "first" from which a recollector begins his search, however, is sometimes a time that is known and sometimes a thing that is known. With respect to the time, he sometimes begins from now, i.e. from teh present time proceeding into the past, the memory of which he is seeking (e.g. if he is seeking to remember what he did four days ago, this is how he meditates on the matter: "I did this today, that yesterday, and something else the day before," and in this fashion he arrives at what he did three days ago by tracing things back according to the sequence of the customary motions). Sometimes, however, he begins from some other time (e.g. if someone remembers what he did a week ago and has forgotten what he did three days ago, he will proceed by coming down to the sixth day and will proceed in the same way until he reaches the third day before, or he may also go up to a day two weeks ago also starting from a week ago, or to any other past time.)
Sometimes, in like fashion, one may also recollect beginning with something that he remembers and from which he proceeds to another one for three reasons: (1) sometimes one recollects by reason of similitude (as when one remembers Socrates, and from this Plato, who is like him in wisdom, comes to mind); (2) sometimes, by reason of contrariety (as when one remembers Hector, and Achilles therefore comes to mind); (3) and sometimes one recollects by reason of some proximity (as when the son comes to mind when one remembers the father, and the same reason holds for any other sort of proximity, whether of association, of place, or of time.
[Translation from St. Thomas Aquinas. Commentaries on Aristotle's "On Sense and What Is Sensed" and "On Memory and Recollection". Kevin White and Edward M. Macierowski, trs. Catholic University of America Press (Washington, DC: 2005) 212-213.]
It was passages like this that led Samuel Taylor Coleridge to think that Hume might have ripped off the Angelic Doctor. There is a famous passage in the Biographia Litteraria (Chapter V) about it:
In consulting the excellent commentary of St. Thomas Aquinas on the Parva Naturalia of Aristotle, I was struck at once with its close resemblance to Hume's Essay on association. The main thoughts were the same in both, the order of the thoughts was the same, and even the illustrations differed only by Hume's occasional substitution of more modern examples. I mentioned the circumstance to several of my literary acquaintances, who admitted the closeness of the resemblance, and that it seemed too great to be explained by mere coincidence; but they thought it improbable that Hume should have held the pages of the angelic Doctor worth turning over. But some time after Mr. Payne, of the King's mews, shewed Sir James Mackintosh some odd volumes of St. Thomas Aquinas, partly perhaps from having heard that Sir James (then Mr.) Mackintosh had in his lectures passed a high encomium on this canonized philosopher, but chiefly from the fact, that the volumes had belonged to Mr. Hume, and had here and there marginal marks and notes of reference in his own hand writing. Among these volumes was that which contains the Parva Naturalia, in the old Latin version, swathed and swaddled in the commentary afore mentioned!
(The Parva Naturalia is the larger set of works that includes Aristotle's works on sense and memory.) Compare the above passage with Hume's essay on Assocation (it isn't clear what Coleridge means by the order being the same). While this would be really cool if true, I think (alas) that Coleridge scholars have determined (from later letters of Sir James Mackintosh) that Coleridge either misunderstood or was misinformed about the nature of the volumes in question -- they did not have Hume's marginalia and (if I remember correctly) were perhaps not owned by Hume.
Coleridge is not the only one to be struck by the similarity however. Some time ago I posted a passage from Beattie's essay on Imagination in which he remarks on how Aristotle-like Hume's principles of association are.
Poor Hume! He was so proud of his principles of association; in the Abstract he even went so far as to say, "if any thing can intitle the author to so glorious a name as that of an inventor, 'tis the use he makes of the principle of the association of ideas, which enters into most of his philosophy." Originality is a very ironic goddess; she likes playing tricks on people. But (in fairness to Hume) neither Aristotle nor Aquinas make such considerable use of association as he does, and much of what he says in that regard is certainly very original.