Reply Obj. 2: Prudence has more in common with art than a speculative habit has, if we consider their subject and matter: for they are both in the thinking part of the soul, and about things that may be otherwise than they are. But if we consider them as virtues, then art has more in common with the speculative habits, as is clear from what has been said.
Reply Obj. 3: Prudence is of good counsel about matters regarding man's entire life, and the end of human life. But in some arts there is counsel about matters concerning the ends proper to those arts. Hence some men, in so far as they are good counselors in matters of warfare, or seamanship, are said to be prudent officers or pilots, but not simply prudent: only those are simply prudent who give good counsel about all the concerns of life. ________________________
FIFTH ARTICLE [I-II, Q. 57, Art. 5]
Whether Prudence Is a Virtue Necessary to Man?
Objection 1: It would seem that prudence is not a virtue necessary to lead a good life. For as art is to things that are made, of which it is the right reason, so is prudence to things that are done, in respect of which we judge of a man's life: for prudence is the right reason about these things, as stated in Ethic. vi, 5. Now art is not necessary in things that are made, save in order that they be made, but not after they have been made. Neither, therefore is prudence necessary to man in order to lead a good life, after he has become virtuous; but perhaps only in order that he may become virtuous.
Obj. 2: Further, "It is by prudence that we are of good counsel," as stated in Ethic. vi, 5. But man can act not only from his own, but also from another's good counsel. Therefore man does not need prudence in order to lead a good life, but it is enough that he follow the counsels of prudent men.
Obj. 3: Further, an intellectual virtue is one by which one always tells the truth, and never a falsehood. But this does not seem to be the case with prudence: for it is not human never to err in taking counsel about what is to be done; since human actions are about things that may be otherwise than they are. Hence it is written (Wis. 9:14): "The thoughts of mortal men are fearful, and our counsels uncertain." Therefore it seems that prudence should not be reckoned an intellectual virtue.
On the contrary, It is reckoned with other virtues necessary for human life, when it is written (Wis. 8:7) of Divine Wisdom: "She teacheth temperance and prudence and justice and fortitude, which are such things as men can have nothing more profitable in life."
I answer that, Prudence is a virtue most necessary for human life. For a good life consists in good deeds. Now in order to do good deeds, it matters not only what a man does, but also how he does it; to wit, that he do it from right choice and not merely from impulse or passion. And, since choice is about things in reference to the end, rectitude of choice requires two things: namely, the due end, and something suitably ordained to that due end. Now man is suitably directed to his due end by a virtue which perfects the soul in the appetitive part, the object of which is the good and the end. And to that which is suitably ordained to the due end man needs to be rightly disposed by a habit in his reason, because counsel and choice, which are about things ordained to the end, are acts of the reason. Consequently an intellectual virtue is needed in the reason, to perfect the reason, and make it suitably affected towards things ordained to the end; and this virtue is prudence. Consequently prudence is a virtue necessary to lead a good life.
Reply Obj. 1: The good of an art is to be found, not in the craftsman, but in the product of the art, since art is right reason about things to be made: for since the making of a thing passes into external matter, it is a perfection not of the maker, but of the thing made, even as movement is the act of the thing moved: and art is concerned with the making of things. On the other hand, the good of prudence is in the active principle, whose activity is its perfection: for prudence is right reason about things to be done, as stated above (A. 4). Consequently art does not require of the craftsman that his act be a good act, but that his work be good. Rather would it be necessary for the thing made to act well (e.g. that a knife should carve well, or that a saw should cut well), if it were proper to such things to act, rather than to be acted on, because they have not dominion over their actions. Wherefore the craftsman needs art, not that he may live well, but that he may produce a good work of art, and have it in good keeping: whereas prudence is necessary to man, that he may lead a good life, and not merely that he may be a good man.