The virtue of man is the perfection of the nature of man. For every being becomes perfect, and arrives at the summit of excellence according to the proper nature of its virtue. Thus the virtue of a horse, is that which leads the nature of a horse to its summit. And the same reasoning is applicable to the several parts of a thing. Thus the virtue of the eyes is acuteness of vision: and this in the nature of the eyes is the summit. The virtue of the ears also, is acuteness of hearing: and this is the summit of the nature of the ears. Thus too, the virtue of the feet is swiftness: and this is the summit of the nature of the feet. It is necessary however, that every virtue should have these three things, reason, power, and deliberate choice; reason indeed, by which it judges and contemplates; power, by which it prohibits and vanquishes; and deliberate choice, by which it loves and delights in [what is proper]. To judge therefore, and contemplate, pertain to the dianoetic part of the soul; but to prohibit and vanquish are the peculiarity of the irrational[66] part of the soul; and to love and delight in what is proper, pertain to both the rational and irrational parts. For deliberate choice consists of dianoia [or the discursive energy of reason] and appetite. Dianoia therefore, belongs to the rational, but appetite to the irrational part of the soul. The multitude however, of all the virtues, may be perceived from the parts of the soul; and in a similar manner the generation and nature of virtue. For of the parts of the soul, there are two that rank as the first, viz. the rational and the irrational parts. And the rational part indeed, is that by which we judge and contemplate; but the irrational part is that by which we are impelled and desire. These however, are either concordant or discordant with each other. But the contest and dissonance between them, are produced through excess and defect. It is evident therefore, that when the rational vanquishes the irrational part of the soul, endurance and continence are produced; and that when the former leads, and the latter follows, and both accord with each other, then virtue is generated. Hence, endurance and continence are generated accompanied with pain; but endurance resists pain, and continence pleasure. Incontinence however, and effeminacy, neither resist nor vanquish [pleasure]. And on this account it happens that men fly from good through pain, but reject it through pleasure. Praise likewise, and blame, and every thing beautiful in human conduct are produced in these parts of the soul. And in short, the nature of virtue derives its subsistence after this manner.

The species however, and the parts of it, may be surveyed as follows: Since there are two parts of the soul, the rational and the irrational; the latter is divided into the irascible and appetitive. And the rational part, indeed, is that by which we judge and contemplate; but the irrational part is that by which we are impelled and desire. And of this, that which is as it were adapted to defend us, and revenge incidental molestations, is denominated the irascible part; but that which is as it were orectic of, and desires to preserve the proper constitution of the body, is the appetitive part. It is evident therefore, that the multitude of the virtues, their differences, and their peculiarities, follow conformably to these parts of the soul.