virtue?

(6) Whether the will can be the subject of virtue?
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FIRST ARTICLE [I-II, Q. 56, Art. 1]

Whether the Subject of Virtue Is a Power of the Soul?

Objection 1: It would seem that the subject of virtue is not a power
of the soul. For Augustine says (De Lib. Arb. ii, 19) that "virtue is
that by which we live righteously." But we live by the essence of the
soul, and not by a power of the soul. Therefore virtue is not a
power, but in the essence of the soul.

Obj. 2: Further, the Philosopher says (Ethic. ii, 6) that "virtue is
that which makes its possessor good, and his work good likewise." But
as work is set up by power, so he that has a virtue is set up by the
essence of the soul. Therefore virtue does not belong to the power,
any more than to the essence of the soul.

Obj. 3: Further, power is in the second species of quality. But
virtue is a quality, as we have said above (Q. 55, A. 4): and quality
is not the subject of quality. Therefore a power of the soul is not
the subject of virtue.

_On the contrary,_ "Virtue is the limit of power" (De Coelo ii). But
the limit is in that of which it is the limit. Therefore virtue is in
a power of the soul.

_I answer that,_ It can be proved in three ways that virtue belongs
to a power of the soul. First, from the notion of the very essence of
virtue, which implies perfection of a power; for perfection is in
that which it perfects. Secondly, from the fact that virtue is an
operative habit, as we have said above (Q. 55, A. 2): for all
operation proceeds from the soul through a power. Thirdly, from the
fact that virtue disposes to that which is best: for the best is the
end, which is either a thing's operation, or something acquired by an
operation proceeding from the thing's power. Therefore a power of the
soul is the subject of virtue.

Reply Obj. 1: "To live" may be taken in two ways. Sometimes it is
taken for the very existence of the living thing: in this way it
belongs to the essence of the soul, which is the principle of
existence in the living thing. But sometimes "to live" is taken for
the operation of the living thing: in this sense, by virtue we live
righteously, inasmuch as by virtue we perform righteous actions.

Reply Obj. 2: Good is either the end, or something referred to the
end. And therefore, since the good of the worker consists in the
work, this fact also, that virtue makes the worker good, is referred
to the work, an