17. Putting aside, then, for a little while all other things, of which the mind is certain concerning itself, let us especially consider and discuss these three -- memory, understanding, will. For we may commonly discern in these three the character of the abilities of the young also; since the more tenaciously and easily a boy remembers, and the more acutely he understands, and the more ardently he studies, the more praiseworthy is he in point of ability. But when the question is about any one's learning, then we ask not how solidly and easily he remembers, or how shrewdly he understands; but what it is that he remembers, and what it is that he understands. And because the mind is regarded as praiseworthy, not only as being learned, but also as being good, one gives heed not only to what he remembers and what he understands, but also to what he wills (velit); not how ardently he wills, but first what it is he wills, and then how greatly he wills it. For the mind that loves eagerly is then to be praised, when it loves that which ought to be loved eagerly. Since, then, we speak of these three -- ability, knowledge, use -- the first of these is to be considered under the three heads, of what a man can do in memory, and understanding, and will. The second of them is to be considered in regard to that which any one has in his memory and in his understanding, which he has attained by a studious will. But the third, viz. use, lies in the will, which handles those things that are contained in the memory and understanding, whether it refer them to anything further, or rest satisfied with them as an end. For to use, is to take up something into the power of the will; and to enjoy, is to use with joy, not any longer of hope, but of the actual thing. Accordingly, every one who enjoys, uses; for he takes up something into the power of the will, wherein he also is satisfied as with an end. But not every one who uses, enjoys, if he has sought after that, which he takes up into the power of the will, not on account of the thing itself, but on account of something else.
18. Since, then, these three, memory, understanding, will, are not three lives, but one life; nor three minds, but one mind; it follows certainly that neither are they three substances, but one substance. Since memory, which is called life, and mind, and substance, is so called in respect to itself; but it is called memory, relatively to something. And I should say the same also of understanding and of will, since they are called understanding and will relatively to something; but each in respect to itself is life, and mind, and essence. And hence these three are one, in that they are one life, one mind, one essence; and whatever else they are severally called in respect to themselves, they are called also together, not plurally, but in the singular number. But they are three, in that wherein they are mutually referred to each other; and if they were not equal, and this not only each to each, but also each to all, they certainly could not mutually contain each other; for not only is each contained by each, but also all by each. For I remember that I have memory and understanding, and will; and I understand that I understand, and will, and remember; and I will that I will, and remember, and understand; and I remember together my whole memory, and understanding, and will. For that of my memory which I do not remember, is not in my memory; and nothing is so much in the memory as memory itself. Therefore I remember the whole memory. Also, whatever I understand I know that I understand, and I know that I will whatever I will; but whatever I know I remember. Therefore I remember the whole of my understanding, and the whole of my will. Likewise, when I understand these three things, I understand them together as whole. For there is none of things intelligible which I do not understand, except what I do not know; but what I do not know, I neither remember, nor will. Therefore, whatever of things intelligible I do not understand, it follows also that I neither remember nor will. And whatever of things intelligible I remember and will, it follows that I understand. My will also embraces my whole understanding and my whole memory whilst I use the whole that I understand and remember. And, therefore, while all are mutually comprehended by each, and as wholes, each as a whole is equal to each as a whole, and each as a whole at the same time to all as wholes; and these three are one, one life, one mind, one essence.