Memory Retains All Things.

20. All these things I retain in my memory, and how I learnt them I retain. I retain also many things which I have heard most falsely objected against them, which though they be false, yet is it not false that I have remembered them; and I remember, too, that I have distinguished between those truths and these falsehoods uttered against them; and I now see that it is one thing to distinguish these things, another to remember that I often distinguished them, when I often reflected upon them. I both remember, then, that I have often understood these things, and what I now distinguish and comprehend I store away in my memory, that hereafter I may remember that I understood it now. Therefore also I remember that I have remembered; so that if afterwards I shall call to mind that I have been able to remember these things, it will be through the power of memory that I shall call it to mind.

Conf 12.14.1