d, and principally in _De Libero
Arbitrio_ ii, 19.

_I answer that,_ This definition comprises perfectly the whole
essential notion of virtue. For the perfect essential notion of
anything is gathered from all its causes. Now the above definition
comprises all the causes of virtue. For the formal cause of virtue,
as of everything, is gathered from its genus and difference, when it
is defined as "a good quality": for "quality" is the genus of virtue,
and the difference, "good." But the definition would be more suitable
if for "quality" we substitute "habit," which is the proximate genus.

Now virtue has no matter "out of which" it is formed, as neither has
any other accident; but it has matter "about which" it is concerned,
and matter "in which" it exists, namely, the subject. The matter
about which virtue is concerned is its object, and this could not be
included in the above definition, because the object fixes the virtue
to a certain species, and here we are giving the definition of virtue
in general. And so for material cause we have the subject, which is
mentioned when we say that virtue is a good quality "of the mind."

The end of virtue, since it is an operative habit, is operation. But
it must be observed that some operative habits are always referred to
evil, as vicious habits: others are sometimes referred to good,
sometimes to evil; for instance, opinion is referred both to the true
and to the untrue: whereas virtue is a habit which is always referred
to good: and so the distinction of virtue from those habits which are
always referred to evil, is expressed in the words "by which we live
righteously": and its distinction from those habits which are
sometimes directed unto good, sometimes unto evil, in the words, "of
which no one makes bad use."

Lastly, God is the efficient cause of infused virtue, to which this
definition applies; and this is expressed in the words "which God
works in us without us." If we omit this phrase, the remainder of the
definition will apply to all virtues in general, whether acquired or
infused.

Reply Obj. 1: That which is first seized by the intellect is being:
wherefore everything that we apprehend we consider as being, and
consequently as one, and as good, which are convertible with being.
Wherefore we say that essence is being and is one and is good; and
that oneness is being and one and good: and in like manner goodness.
But this is not the case with specific forms, as whi