e he is
just, or temperate; and in like manner as regards other such virtues.
And since virtue is that "which makes its possessor good, and his
work good likewise," these latter habits are called virtuous simply:
because they make the work to be actually good, and the subject good
simply. But the first kind of habits are not called virtues simply:
because they do not make the work good except in regard to a certain
aptness, nor do they make their possessor good simply. For through
being gifted in science or art, a man is said to be good, not simply,
but relatively; for instance, a good grammarian or a good smith. And
for this reason science and art are often divided against virtue;
while at other times they are called virtues (Ethic. vi, 2).

Hence the subject of a habit which is called a virtue in a relative
sense, can be the intellect, and not only the practical intellect,
but also the speculative, without any reference to the will: for thus
the Philosopher (Ethic. vi, 3) holds that science, wisdom and
understanding, and also art, are intellectual virtues. But the
subject of a habit which is called a virtue simply, can only be the
will, or some power in so far as it is moved by the will. And the
reason of this is, that the will moves to their acts all those other
powers that are in some way rational, as we have said above (Q. 9, A.
1; Q. 17, AA. 1, 5; I, Q. 82, A. 4): and therefore if man do well
actually, this is because he has a good will. Therefore the virtue
which makes a man to do well actually, and not merely to have the
aptness to do well, must be either in the will itself; or in some
power as moved by the will.

Now it happens that the intellect is moved by the will, just as are
the other powers: for a man considers something actually, because he
wills to do so. And therefore the intellect, in so far as it is
subordinate to the will, can be the subject of virtue absolutely so
called. And in this way the speculative intellect, or the reason, is
the subject of Faith: for the intellect is moved by the command of
the will to assent to what is of faith: for "no man believeth, unless
he will" [*Augustine: Tract. xxvi in Joan.]. But the practical
intellect is the subject of prudence. For since prudence is the right
reason of things to be done, it is a condition thereof that man be
rightly disposed in regard to the principles of this reason of things
to be done, that is in regard to their ends, to which man is right