Reply Obj. 2: The Philosopher says that there is a virtue of art, because art does not require rectitude of the appetite; wherefore in order that a man may make right use of his art, he needs to have a virtue which will rectify his appetite. Prudence however has nothing to do with the matter of art, because art is both directed to a particular end, and has fixed means of obtaining that end. And yet, by a kind of comparison, a man may be said to act prudently in matters of art. Moreover in certain arts, on account of the uncertainty of the means for obtaining the end, there is need for counsel, as for instance in the arts of medicine and navigation, as stated in Ethic. iii, 3.
Reply Obj. 3: This saying of the wise man does not mean that prudence itself should be moderate, but that moderation must be imposed on other things according to prudence. _______________________
FIFTH ARTICLE [II-II, Q. 47, Art. 5]
Whether Prudence Is a Special Virtue?
Objection 1: It would seem that prudence is not a special virtue. For no special virtue is included in the definition of virtue in general, since virtue is defined (Ethic. ii, 6) "an elective habit that follows a mean appointed by reason in relation to ourselves, even as a wise man decides." Now right reason is reason in accordance with prudence, as stated in Ethic. vi, 13. Therefore prudence is not a special virtue.
Obj. 2: Further, the Philosopher says (Ethic. vi, 13) that "the effect of moral virtue is right action as regards the end, and that of prudence, right action as regards the means." Now in every virtue certain things have to be done as means to the end. Therefore prudence is in every virtue, and consequently is not a special virtue.
Obj. 3: Further, a special virtue has a special object. But prudence has not a special object, for it is right reason "applied to action" (Ethic. vi, 5); and all works of virtue are actions. Therefore prudence is not a special virtue.
On the contrary, It is distinct from and numbered among the other virtues, for it is written (Wis. 8:7): "She teacheth temperance and prudence, justice and fortitude."
I answer that, Since acts and habits take their species from their objects, as shown above (I-II, Q. 1, A. 3; Q. 18, A. 2; Q. 54, A. 2), any habit that has a corresponding special object, distinct from other objects, must needs be a special habit, and if it be a good habit, it must be a special virtue. Now an object is called special, not merely according to the consideration of its matter, but rather according to its formal aspect, as explained above (I-II, Q. 54, A. 2, ad 1). Because one and the same thing is the subject matter of the acts of different habits, and also of different powers, according to its different formal aspects. Now a yet greater difference of object is requisite for a difference of powers than for a difference of habits, since several habits are found in the same power, as stated above (I-II, Q. 54, A. 1). Consequently any difference in the aspect of an object, that requires a difference of powers, will a fortiori require a difference of habits.
Accordingly we must say that since prudence is in the reason, as stated above (A. 2), it is differentiated from the other intellectual virtues by a material difference of objects. Wisdom, knowledge and understanding are about necessary things, whereas art and prudence are about contingent things, art being concerned with things made, that is, with things produced in external matter, such as a house, a knife and so forth; and prudence, being concerned with things done, that is, with things that have their being in the doer himself, as stated above (I-II, Q. 57, A. 4). On the other hand prudence is differentiated from the moral virtues according to a formal aspect distinctive of powers, i.e. the intellective power, wherein is prudence, and the appetitive power, wherein is moral virtue. Hence it is evident that prudence is a special virtue, distinct from all other virtues.