The topic of memory in Augustine's thought includes much of his philosophy of mind, for memory is not a distinct power or faculty of the soul, but the mind itself, from which memory, understanding, or will are distinguished only in terms of their different activities. Memory for Augustine has not merely the rather straightforward role of retaining recollections of past experiences, but also the much more problematic tasks of holding in mind present realities and even of anticipating the future. Augustine's account of memory shows a marked development from his early writings, in which he accepted a Platonic doctrine of reminiscence, up to the works of his maturity, in which he clearly rejects almost all, if not all, traces of such a teaching. In the Confessions, Augustine devotes the first half of Book 10 to a description of the contents of his memory as he searches for God, and in Book 11 memory plays a key role in the perception of time. In De Trinitate, Augustine finds in the memory, understanding, and will of the human soul a series of psychological analogies or images of the three persons in one God.