The principles of all virtue are three; knowledge, power, and deliberate choice. And knowledge indeed, is that by which we contemplate and form a judgment of things; power is as it were a certain strength of the nature[69] from which we derive our subsistence, and is that which gives stability to our actions; and deliberate choice is as it were certain hands of the soul by which we are impelled to, and lay hold on the objects of our choice. The order of the soul also subsists as follows: One part of it is the reasoning power, another part is anger, and another is desire. And the reasoning power indeed, is that which has dominion over knowledge; anger is that which rules over the ardent impulses of the soul; and desire is that which willingly rules over appetite. When therefore, these three pass into one, so as to exhibit one co-adaptation, then virtue and concord are produced in the soul; but when they are seditious, and divulsed from each other, then vice and discord are generated in the soul. And when the reasoning power prevails over the irrational parts of the soul, then endurance and continence are produced; endurance indeed, in the retention of pains; but continence in the abstinence from pleasures. But when the irrational parts of the soul prevail over the reasoning power, then effeminacy and incontinence are produced; effeminacy indeed, in flying from pain; but incontinence, in the being vanquished by pleasures. When however, the better part of the soul governs, but the less excellent part is governed; and the former leads, but the latter follows, and both consent, and are concordant with each other, then virtue and every good are generated in the whole soul. When likewise the appetitive follows the reasoning part of the soul, then temperance is produced; but when this is the case with the irascible part, fortitude is produced; and when it takes place in all the parts of the soul, then justice is the result. For justice is that which separates all the vices and all the virtues of the soul from each other. And justice is a certain established order of the apt conjunction of the parts of the soul, and perfect and supreme virtue. For every good is contained in this; but the other goods of the soul cannot subsist without this. Hence justice possesses great strength both among Gods and men. For this virtue contains the bond by which the whole and the universe are held together, and also by which Gods and men are connected. Justice therefore, is said to be Themis among the celestial, but Dice among the terrestrial Gods; and Law among men. These assertions however, are indications and symbols, that justice is the supreme virtue. Hence virtue, when it consists in contemplating and judging, is called prudence; when in sustaining things of a dreadful nature, it is denominated fortitude; when in restraining pleasure, temperance; and when in abstaining from gain, and from injuring our neighbours, justice.

Moreover, the arrangement of virtue according to right reason, and the transgression of it contrary to right reason, produce [in the former case] a tendency to the decorous as the final mark, and [in the latter] the frustration of it. The decorous however, is that which ought to be. But this does not require either addition or ablation; since it is that which it is requisite to be. But of the indecorous there are two species; one of which is excess, and the other defect. And excess indeed, is more, but deficiency is less, than is decorous. Virtue also, is a certain habit of the decorous. Hence it is directly, both a summit and a medium. For thus, things that are decorous are both media and summits. They are media indeed, because they fall between excess and deficiency; but they are summits, because they do not require either addition or ablation. For they are the very things themselves which they ought to be.

Since however, the virtue of manners is conversant with the passions, but of the passions pleasure and pain are supreme, it is evident that virtue does not consist in extirpating the passions of the soul, pleasure and pain, but in co-harmonizing them. For neither does health, which is a certain apt mixture of the powers of the body, consist in expelling the cold and the hot, the moist and the dry; but in these being [appropriately] mingled together. For it is as it were, a certain symmetry of these. Thus too, in music, concord does not consist in expelling the sharp and the flat; but when these are co-harmonized, then concord is produced, and dissonance is exterminated. In a similar manner, the hot and the cold, the moist and the dry, being harmoniously mingled together, health is produced, and disease destroyed. But when anger, and desire are co-harmonized, the vices and the [other] passions are extirpated, and the virtues and manners are ingenerated. Deliberate choice however, in beautiful conduct, is the greatest peculiarity of the virtue of manners. For it is possible to use reason and power without virtue; but it is not possible to use deliberate choice without it. For deliberate choice indicates the dignity of manners. Hence also, the reasoning power subduing by force anger and desire, produces continence and endurance. And again, when the reasoning power is violently dethroned by the irrational parts, then incontinence and effeminacy are produced. Such dispositions however, of the soul as these, are half-perfect virtues, and half-perfect vices. For the reasoning power of the soul is [according to its natural subsistence] in a healthy, but the irrational parts are in a diseased condition. And so far indeed, as anger and desire are governed and led by the rational part of the soul, continence and endurance become virtues; but so far as this is effected by violence, and not voluntarily, they become vices. For it is necessary that virtue should perform such things as are fit, not with pain, but with pleasure. Again, so far as anger and desire govern the reasoning power, effeminacy and incontinence are produced, which are certain vices. But so far, as they gratify the passions with pain, knowing that they are erroneous, in consequence of the eye of the soul being sane,—so far as this is the case, they are not vices. Hence, it is evident that virtue must necessarily perform what is fit voluntarily; that which is involuntary indeed, not being without pain and fear; and that which is voluntary, not subsisting without pleasure and delight.

By division also it will at the same time be found that this is the case. For knowledge and the perception of things, are the province of the rational part of the soul; but power pertains to the irrational part. For not to be able to resist pain, or to vanquish pleasure, is the peculiarity of the irrational part of the soul. But deliberate choice subsists in both these, viz. in the rational; and also in the irrational part. For it consists of dianoia and appetite; of which, dianoia indeed, pertains to the rational, but appetite to the irrational part. Hence every virtue consists in a co-adaptation of the parts of the soul; and both will and deliberate choice, entirely subsist in virtue.

Universally therefore, virtue is a certain co-adaptation of the irrational parts of the soul to the rational part. Virtue however, is produced through pleasure and pain receiving the boundary of that which is fit. For true virtue is nothing else than the habit of that which is fit. But the fit, or the decorous, is that which ought to be; and the unfit, or indecorous, is that which ought not to be. Of the indecorous however, there are two species, viz. excess and defect. And excess indeed, is more than is fit; but defect is less than is fit. But since the fit is that which ought to be, it is both a summit and a middle. It is a summit indeed, because it neither requires ablation, nor addition; but it is a middle, because it subsists between excess and defect. The fit, however, and the unfit, are to each other as the equal and the unequal that which is arranged, and that which is without arrangement; and both the two former and the two latter are finite and infinite.[70] On this account, the parts of the unequal are referred to the middle, but not to each other. For the angle is called obtuse which is greater than a right angle; but that is called acute, which is less than a right angle. The right line also [in a circle] is greater, which surpasses that which is drawn from the center. And the day is longer indeed, which exceeds that of the equinox. Diseases, likewise, of the body are generated, through the body becoming more hot or more cold [than is proper]. For that which is more hot [than is fit] exceeds moderation; and that which is more cold [than is fit] is below mediocrity. The soul also, and such things as pertain to it, have this disposition and analogy. For audacity indeed, is an excess of the decorous in the endurance of things of a dreadful nature; but timidity is a deficiency of the, decorous. And prodigality is an excess of what is fit in the expenditure of money; but illiberality is a deficiency in this. And rage indeed, is an excess of the decorous in the impulse of the irascible part of the soul; but insensibility is a deficiency of this. The same reasoning likewise applies to the opposition of the other dispositions of the soul. It is necessary however, that virtue, since it is a habit of the decorous, and a medium of the passions, should neither be [wholly] impassive, nor immoderately passive. For impassivity indeed, causes the soul to be unimpelled, and to be without an enthusiastic tendency to the beautiful in conduct; but immoderate passivity causes it to be full of perturbation, and inconsiderate. It is necessary therefore, that passion should so present itself to the view, in virtue, as shadow and outline in a picture. For the animated and the delicate, and that which imitates the truth, in conjunction with goodness of colors, are especially effected in a picture through these [i.e. through shadow and outline]. But the passions of the soul are animated by the natural incitation and enthusiasm of virtue. For virtue is generated from the passions, and when generated, again subsists together with them; just as that which is well harmonized consists of the sharp and the flat, that which is well mingled consists of the hot and the cold, and that which is in equilibrium derives its equality of weight from the heavy and the light. It is not therefore necessary to take away the passions of the soul; for neither would this be profitable; but it is requisite that they should be co-harmonized with the rational part, in conjunction with fitness and mediocrity.