What, then, is to be said of the mind of an infant, which is still so small, and buried in such profound ignorance of things, that the mind of a man which knows anything shrinks from the darkness of it? Is that too to be believed to know itself; but that, as being too intent upon those things which it has begun to perceive through the bodily senses, with the greater delight in proportion to their novelty, it is not able indeed to be ignorant of itself, but is also not able to think of itself? Moreover, how intently it is bent upon sensible things that are without it, may be conjectured from this one fact, that it is so greedy of sensible light, that if any one through carelessness, or ignorance of the possible consequences, place a light at nighttime where an infant is lying down, on that side to which the eyes of the child so lying down can be bent, but its neck cannot be turned, the gaze of that child will be so fixed in that direction, that we have known some to have come to squint by this means, in that the eyes retained that form which habit in some way impressed upon them while tender and soft. In the case, too, of the other bodily senses, the souls of infants, as far as their age permits, so narrow themselves as it were, and are bent upon them, that they either vehemently detest or vehemently desire that only which offends or allures through the flesh, but do not think of their own inward self, nor can be made to do so by admonition; because they do not yet know the signs that express admonition, whereof words are the chief, of which as of other things they are wholly ignorant. And that it is one thing not to know oneself, another not to think of oneself, we have shown already in the same book.
8. But let us pass by the infantine age, since we cannot question it as to what goes on within itself, while we have ourselves pretty well forgotten it. Let it suffice only for us hence to be certain, that when man has come to be able to think of the nature of his own mind, and to find out what is the truth, he will find it nowhere else but in himself. And he will find, not what he did not know, but that of which he did not think. For what do we know, if we do not know what is in our own mind; when we can know nothing at all of what we do know, unless by the mind?