Reply Obj. 2:  In order that man may make good use of the art he has, he needs a good will, which is perfected by moral virtue; and for this reason the Philosopher says that there is a virtue of art; namely, a moral virtue, in so far as the good use of art requires a moral virtue.  For it is evident that a craftsman is inclined by justice, which rectifies his will, to do his work faithfully.

Reply Obj. 3:  Even in speculative matters there is something by way of work:  e.g. the making of a syllogism or of a fitting speech, or the work of counting or measuring.  Hence whatever habits are ordained to such like works of the speculative reason, are, by a kind of comparison, called arts indeed, but “liberal” arts, in order to distinguish them from those arts that are ordained to works done by the body, which arts are, in a fashion, servile, inasmuch as the body is in servile subjection to the soul, and man, as regards his soul, is free (liber).  On the other hand, those sciences which are not ordained to any such like work, are called sciences simply, and not arts.  Nor, if the liberal arts be more excellent, does it follow that the notion of art is more applicable to them. ________________________

FOURTH ARTICLE [I-II, Q. 57, Art. 4]

Whether Prudence Is a Distinct Virtue from Art?

Objection 1:  It would seem that prudence is not a distinct virtue from art.  For art is the right reason about certain works.  But diversity of works does not make a habit cease to be an art; since there are various arts about works widely different.  Since therefore prudence is also right reason about works, it seems that it too should be reckoned a virtue.

Obj. 2:  Further, prudence has more in common with art than the speculative habits have; for they are both “about contingent matters that may be otherwise than they are” (Ethic. vi, 4, 5).  Now some speculative habits are called arts.  Much more, therefore, should prudence be called an art.

Obj. 3:  Further, it belongs to prudence, “to be of good counsel” (Ethic. vi, 5).  But counselling takes place in certain arts also, as stated in Ethic. iii, 3, e.g. in the arts of warfare, of seamanship, and of medicine.  Therefore prudence is not distinct from art.

On the contrary, The Philosopher distinguishes prudence from art (Ethic. vi, 5).

I answer that, Where the nature of virtue differs, there is a different kind of virtue.  Now it has been stated above (A. 1; Q. 56, A. 3) that some habits have the nature of virtue, through merely conferring aptness for a good work:  while some habits are virtues, not only through conferring aptness for a good work, but also through conferring the use.  But art confers the mere aptness for good work; since it does not regard the appetite; whereas prudence confers not only aptness for a good work, but also the use:  for it regards the appetite, since it presupposes the rectitude thereof.