Whether any other virtues should be called principal rather than these?
Objection 1: It would seem that other virtues should be called principal rather than these. For, seemingly, the greatest is the principal in any genus. Now "magnanimity has a great influence on all the virtues" (Ethic. iv, 3). Therefore magnanimity should more than any be called a principal virtue.
Objection 2: Further, that which strengthens the other virtues should above all be called a principal virtue. But such is humility: for Gregory says (Hom. iv in Ev.) that "he who gathers the other virtues without humility is as one who carries straw against the wind." Therefore humility seems above all to be a principal virtue.
Objection 3: Further, that which is most perfect seems to be principal. But this applies to patience, according to James 1:4: "Patience hath a perfect work." Therefore patience should be reckoned a principal virtue.
On the contrary, Cicero reduces all other virtues to these four (De Invent. Rhet. ii).
I answer that, As stated above (A 2), these four are reckoned as cardinal virtues, in respect of the four formal principles of virtue as we understand it now. These principles are found chiefly in certain acts and passions. Thus the good which exists in the act of reason, is found chiefly in reason's command, but not in its counsel or its judgment, as stated above (Q 57, A 6). Again, good as defined by reason and put into our operations as something right and due, is found chiefly in commutations and distributions in respect of another person, and on a basis of equality. The good of curbing the passions is found chiefly in those passions which are most difficult to curb, viz. in the pleasures of touch. The good of being firm in holding to the good defined by reason, against the impulse of passion, is found chiefly in perils of death, which are most difficult to withstand.
Accordingly the above four virtues may be considered in two ways. First, in respect of their common formal principles. In this way they are called principal, being general, as it were, in comparison with all the virtues: so that, for instance, any virtue that causes good in reason's act of consideration, may be called prudence; every virtue that causes the good of right and due in operation, be called justice; every virtue that curbs and represses the passions, be called temperance; and every virtue that strengthens the mind against any passions whatever, be called fortitude. Many, both holy doctors, as also philosophers, speak about these virtues in this sense: and in this way the other virtues are contained under them. Wherefore all the objections fail.
Secondly, they may be considered in point of their being denominated, each one from that which is foremost in its respective matter, and thus they are specific virtues, condivided with the others. Yet they are called principal in comparison with the other virtues, on account of the importance of their matter: so that prudence is the virtue which commands; justice, the virtue which is about due actions between equals; temperance, the virtue which suppresses desires for the pleasures of touch; and fortitude, the virtue which strengthens against dangers of death. Thus again do the objections fail: because the other virtues may be principal in some other way, but these are called principal by reason of their matter, as stated above.
I–II · Q. 61, Art. 4: Whether the four cardinal virtues differ from one another?
Whether the four cardinal virtues differ from one another?
Objection 1: It would seem that the above four virtues are not diverse and distinct from one another. For Gregory says (Moral. xxii, 1): "There is no true prudence, unless it be just, temperate and brave; no perfect temperance, that is not brave, just and prudent; no sound fortitude, that is not prudent, temperate and just; no real justice, without prudence, fortitude and temperance." But this would not be so, if the above virtues were distinct from one another: since the different species of one genus do not qualify one another. Therefore the aforesaid virtues are not distinct from one another.
Objection 2: Further, among things distinct from one another the function of one is not attributed to another. But the function of temperance is attributed to fortitude: for Ambrose says (De Offic. xxxvi): "Rightly do we call it fortitude, when a man conquers himself, and is not weakened and bent by any enticement." And of temperance he says (De Offic. xliii, xlv) that it "safeguards the manner and order in all things that we decide to do and say." Therefore it seems that these virtues are not distinct from one another.
Objection 3: Further, the Philosopher says (Ethic. ii, 4) that the necessary conditions of virtue are first of all "that a man should have knowledge; secondly, that he should exercise choice for a particular end; thirdly, that he should possess the habit and act with firmness and steadfastness." But the first of these seems to belong to prudence which is rectitude of reason in things to be done; the second, i.e. choice, belongs to temperance, whereby a man, holding his passions on the curb, acts, not from passion but from choice; the third, that a man should act for the sake of a due end, implies a certain rectitude, which seemingly belongs to justice; while the last, viz. firmness and steadfastness, belongs to fortitude. Therefore each of these virtues is general in comparison to other virtues. Therefore they are not distinct from one another.
On the contrary, Augustine says (De Moribus Eccl. xi) that "there are four virtues, corresponding to the various emotions of love," and he applies this to the four virtues mentioned above. Therefore the same four virtues are distinct from one another.
I answer that, As stated above (A 3), these four virtues are understood differently by various writers. For some take them as signifying certain general conditions of the human mind, to be found in all the virtues: so that, to wit, prudence is merely a certain rectitude of discretion in any actions or matters whatever; justice, a certain rectitude of the mind, whereby a man does what he ought in any matters; temperance, a disposition of the mind, moderating any passions or operations, so as to keep them within bounds; and fortitude, a disposition whereby the soul is strengthened for that which is in accord with reason, against any assaults of the passions, or the toil involved by any operations. To distinguish these four virtues in this way does not imply that justice, temperance and fortitude are distinct virtuous habits: because it is fitting that every moral virtue, from the fact that it is a "habit," should be accompanied by a certain firmness so as not to be moved by its contrary: and this, we have said, belongs to fortitude. Moreover, inasmuch as it is a "virtue," it is directed to good which involves the notion of right and due; and this, we have said, belongs to justice. Again, owing to the fact that it is a "moral virtue" partaking of reason, it observes the mode of reason in all things, and does not exceed its bounds, which has been stated to belong to temperance. It is only in the point of having discretion, which we ascribed to prudence, that there seems to be a distinction from the other three, inasmuch as discretion belongs essentially to reason; whereas the other three imply a certain share of reason by way of a kind of application (of reason) to passions or operations. According to the above explanation, then, prudence would be distinct from the other three virtues: but these would not be distinct from one another; for it is evident that one and the same virtue is both habit, and virtue, and moral virtue.
Others, however, with better reason, take these four virtues, according as they have their special determinate matter; each of its own matter, in which special commendation is given to that general condition from which the virtue's name is taken as stated above (A 3). In this way it is clear that the aforesaid virtues are distinct habits, differentiated in respect of their diverse objects.
Reply to Objection 1: Gregory is speaking of these four virtues in the first sense given above. It may also be said that these four virtues qualify one another by a kind of overflow. For the qualities of prudence overflow on to the other virtues in so far as they are directed by prudence. And each of the others overflows on to the rest, for the reason that whoever can do what is harder, can do what is less difficult. Wherefore whoever can curb his desires for the pleasures of touch, so that they keep within bounds, which is a very hard thing to do, for this very reason is more able to check his daring in dangers of death, so as not to go too far, which is much easier; and in this sense fortitude is said to be temperate. Again, temperance is said to be brave, by reason of fortitude overflowing into temperance: in so far, to wit, as he whose mind is strengthened by fortitude against dangers of death, which is a matter of very great difficulty, is more able to remain firm against the onslaught of pleasures; for as Cicero says (De Offic. i), "it would be inconsistent for a man to be unbroken by fear, and yet vanquished by cupidity; or that he should be conquered by lust, after showing himself to be unconquered by toil."
From this the Reply to the Second Objection is clear. For temperance observes the mean in all things, and fortitude keeps the mind unbent by the enticements of pleasures, either in so far as these virtues are taken to denote certain general conditions of virtue, or in the sense that they overflow on to one another, as explained above.
Reply to Objection 3: These four general conditions of virtue set down by the Philosopher, are not proper to the aforesaid virtues. They may, however, be appropriated to them, in the way above stated.