13. Let it not then add anything to that which it knows itself to be, when it is bidden to know itself. For it knows, at any rate, that this is said to itself; namely, to the self that is, and that lives, and that understands. But a dead body also is, and cattle live; but neither a dead body nor cattle understand. Therefore it so knows that it so is, and that it so lives, as an understanding is and lives. When, therefore, for example’s sake, the mind thinks itself air, it thinks that air understands; it knows, however, that itself understands, but it does not know itself to be air, but only thinks so. Let it separate that which it thinks itself; let it discern that which it knows; let this remain to it, about which not even have they doubted who have thought the mind to be this corporeal thing or that. For certainly every mind does not consider itself to be air; but some think themselves fire, others the brain, and some one kind of corporeal thing, others another, as I have mentioned before; yet all know that they themselves understand, and are, and live; but they refer understanding to that which they understand, but to be, and to live, to themselves. And no one doubts, either that no one understands who does not live, or that no one lives of whom it is not true that he is; and that therefore by consequence that which understands both is and lives; not as a dead body is which does not live, nor as a soul lives which does not understand, but in some proper and more excellent manner. Further, they know that they will, and they equally know that no one can will who is not and who does not live; and they also refer that will itself to something which they will with that will. They know also that they remember; and they know at the same time that nobody could remember, unless he both was and lived; but we refer memory itself also to something, in that we remember those things. Therefore the knowledge and science of many things are contained in two of these three, memory and understanding; but will must be present, that we may enjoy or use them. For we enjoy things known, in which things themselves the will finds delight for their own sake, and so reposes; but we use those things, which we refer to some other thing which we are to enjoy. Neither is the life of man vicious and culpable in any other way, than as wrongly using and wrongly enjoying. But it is no place here to discuss this.