Objection 1. It would seem that it is not essential to human virtue to be an operative habit. For Tully says (Tuscul. iv) that as health and beauty belong to the body, so virtue belongs to the soul. But health and beauty are not operative habits. Therefore neither is virtue.
Objection 2. Further, in natural things we find virtue not only in reference to act, but also in reference to being: as is clear from the Philosopher (De Coelo i), since some have a virtue to be always, while some have a virtue to be not always, but at some definite time. Now as natural virtue is in natural things, so is human virtue in rational beings. Therefore also human virtue is referred not only to act, but also to being.
Objection 3. Further, the Philosopher says (Phys. vii, text. 17) that virtue "is the disposition of a perfect thing to that which is best." Now the best thing to which man needs to be disposed by virtue is God Himself, as Augustine proves (De Moribus Eccl. 3,6, 14) to Whom the soul is disposed by being made like to Him. Therefore it seems that virtue is a quality of the soul in reference to God, likening it, as it were, to Him; and not in reference to operation. It is not, therefore, an operative habit.
On the contrary, The Philosopher (Ethic. ii, 6) says that "virtue of a thing is that which makes its work good."
I answer that, Virtue, from the very nature of the word, implies some perfection of power, as we have said above (Article 1). Wherefore, since power [The one Latin word 'potentia' is rendered 'potentiality' in the first case, and 'power' in the second] is of two kinds, namely, power in reference to being, and power in reference to act; the perfection of each of these is called virtue. But power in reference to being is on the part of matter, which is potential being, whereas power in reference to act, is on the part of the form, which is the principle of action, since everything acts in so far as it is in act.
Now man is so constituted that the body holds the place of matter, the soul that of form. The body, indeed, man has in common with other animals; and the same is to be said of the forces which are common to the soul and body: and only those forces which are proper to the soul, namely, the rational forces, belong to man alone. And therefore, human virtue, of which we are speaking now, cannot belong to the body, but belongs only to that which is proper to the soul. Wherefore human virtue does not imply reference to being, but rather to act. Consequently it is essential to human virtue to be an operative habit.
Reply to Objection 1. Mode of action follows on the disposition of the agent: for such as a thing is, such is its act. And therefore, since virtue is the principle of some kind of operation, there must needs pre-exist in the operator in respect of virtue some corresponding disposition. Now virtue causes an ordered operation. Therefore virtue itself is an ordered disposition of the soul, in so far as, to wit, the powers of the soul are in some way ordered to one another, and to that which is outside. Hence virtue, inasmuch as it is a suitable disposition of the soul, is like health and beauty, which are suitable dispositions of the body. But this does not hinder virtue from being a principle of operation.
Reply to Objection 2. Virtue which is referred to being is not proper to man; but only that virtue which is referred to works of reason, which are proper to man.
Reply to Objection 3. As God's substance is His act, the highest likeness of man to God is in respect of some operation. Wherefore, as we have said above (Question 3, Article 2), happiness or bliss by which man is made most perfectly conformed to God, and which is the end of human life, consists in an operation.
Source: Summa Theologica (New Advent)