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. ________________________

FOURTH ARTICLE [I-II, Q. 61, Art. 4]

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.

Obj. 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.

Obj. 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.