17. But now when I hear that there are three kinds of questions--"Whether a thing is? What it is? Of what kind it is?"--I do indeed retain the images of the sounds of which these words are composed and I know that those sounds pass through the air with a noise and now no longer exist. But the things themselves which were signified by those sounds I never could reach by any sense of the body nor see them at all except by my mind. And what I have stored in my memory was not their signs, but the things signified.
How they got into me, let them tell who can. For I examine all the gates of my flesh, but I cannot find the door by which any of them entered. For the eyes say, "If they were colored, we reported that." The ears say, "If they gave any sound, we gave notice of that." The nostrils say, "If they smell, they passed in by us." The sense of taste says, "If they have no flavor, don't ask me about them." The sense of touch says, "If it had no bodily mass, I did not touch it, and if I never touched it, I gave no report about it."
Whence and how did these things enter into my memory? I do not know. For when I first learned them, it was not that I believed them on the credit of another man's mind, but I recognized them in my own; and I saw them as true, took them into my mind and laid them up, so to say, where I could get at them again whenever I willed. There they were, then, even before I learned them, but they were not in my memory. Where were they, then? How does it come about that when they were spoken of, I could acknowledge them and say, "So it is, it is true," unless they were already in the memory, though far back and hidden, as it were, in the more secret caves, so that unless they had been drawn out by the teaching of another person, I should perhaps never have been able to think of them at all?