says in his
book on the _Predestination of the Saints_ (De Dono Persev. xvi).
Therefore grace is not virtue.

_I answer that,_ Some held that grace and virtue were identical in
essence, and differed only logically--in the sense that we speak of
grace inasmuch as it makes man pleasing to God, or is given
gratuitously--and of virtue inasmuch as it empowers us to act
rightly. And the Master seems to have thought this (Sent. ii, D 27).

But if anyone rightly considers the nature of virtue, this cannot
hold, since, as the Philosopher says (Physic. vii, text. 17), "virtue
is disposition of what is perfect--and I call perfect what is
disposed according to its nature." Now from this it is clear that the
virtue of a thing has reference to some pre-existing nature, from the
fact that everything is disposed with reference to what befits its
nature. But it is manifest that the virtues acquired by human acts of
which we spoke above (Q. 55, seqq.) are dispositions, whereby a man
is fittingly disposed with reference to the nature whereby he is a
man; whereas infused virtues dispose man in a higher manner and
towards a higher end, and consequently in relation to some higher
nature, i.e. in relation to a participation of the Divine Nature,
according to 2 Pet. 1:4: "He hath given us most great and most
precious promises; that by these you may be made partakers of the
Divine Nature." And it is in respect of receiving this nature that we
are said to be born again sons of God.

And thus, even as the natural light of reason is something besides
the acquired virtues, which are ordained to this natural light, so
also the light of grace which is a participation of the Divine Nature
is something besides the infused virtues which are derived from and
are ordained to this light, hence the Apostle says (Eph. 5:8): "For
you were heretofore darkness, but now light in the Lord. Walk then as
children of the light." For as the acquired virtues enable a man to
walk, in accordance with the natural light of reason, so do the
infused virtues enable a man to walk as befits the light of grace.

Reply Obj. 1: Augustine calls "faith that worketh by charity" grace,
since the act of faith of him that worketh by charity is the first
act by which sanctifying grace is manifested.

Reply Obj. 2: Good is placed in the definition of virtue with
reference to its fitness with some pre-existing nature essential or
participated. Now good is not attributed to grace in