Memory is, for Augustine, ultimately a questin of desire, of the right intentio or affection towards that which one remembers. The well-trained memory is one in which good use is made of the “things” in one’s memory. “A character,” he says, “is only to be praised for loving passionately when what it loves deserves to be passionately loved.” He describes the threefold character of disposition, learning and practice (usus) which correspond to the threefold division of memory, understanding and will (which further corresponds to the three rhetorical functions: delighting, teaching, moving). As is typical in his treatment in De Trinitate, the third term is a combination of the first two. Thus the practice of a person’s memory, or its “use,” consists in the “use the will now makes of what the memory and understanding hold, whether it refers them to something else or whether it takes delight in them as ends in themselves.” Therefore, to remember well is to will rightly, to have the proper kind of learned disposition towards that which one remembers [pp. 61-2].
And then, with this in mind, Pete says a couple of pages later:
What follows, then, in the remaining three books of the Confessions, is no mere afterthought, as some have argued. Instead, from what we have seen so far, we are in a position now to understand Books IX-XIII as the actual activity of the memory doing its work, as the plumbing of its unfathomable and mysterious depths. Yet the locus of this activity is not only the individual mind, but the collective memory of the church. The content of that recollection is not the boyhood adventures of Augustine; it is rather the story of God’s way with the world. Thus he begins Book XI with a retelling of the account of creation in Genesis, and concludes in Book XIII with a discussion of the eternal Sabbath. That is to say, Augustine now formally situates his own personal narrative within a larger story, that which the church tells — moreover, that story in whose telling and performing the church is itself enacted [pp. 65-6].