nce, 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.

Reply Obj. 1: This is not a definition of virtue in general, but of
moral virtue, the definition of which fittingly includes an
intellectual virtue, viz., prudence, which has the same matter in
common with moral virtue; because, just as the subject of moral
virtue is something that partakes of reason, so moral virtue has the
aspect of virtue, in so far as it partakes of intellectual virtue.

Reply Obj. 2: This argument proves that prudence helps all the
virtues, and works in all of them; but this does not suffice to prove
that it is