HKB
a believer than when it comes to an unbeliever: since it causes faith in both, in the former by confirming and perfecting it, in the latter by creating it anew.
We might also reply that it is accidental, namely on account of the disposition of the subject, that grace does not cause faith in one who has it already: just as, on the other hand, a second mortal sin does not take away grace from one who has already lost it through a previous mortal sin.
Reply Obj. 4: When living faith becomes lifeless, faith is not changed, but its subject, the soul, which at one time has faith without charity, and at another time, with charity.
FIFTH ARTICLE [II-II, Q. 4, Art. 5]
Objection 1: It would seem that faith is not a virtue. For virtue is directed to the good, since "it is virtue that makes its subject good," as the Philosopher states (Ethic. ii, 6). But faith is directed to the true. Therefore faith is not a virtue.
Obj. 2: Further, infused virtue is more perfect than acquired virtue. Now faith, on account of its imperfection, is not placed among the acquired intellectual virtues, as the Philosopher states (Ethic. vi, 3). Much less, therefore, can it be considered an infused virtue.
Obj. 3: Further, living and lifeless faith are the same species, as stated above (A. 4). Now lifeless faith is not a virtue, since it is not connected with the other virtues. Therefore neither is living faith a virtue.
Obj. 4: Further, the gratuitous graces and the fruits are distinct from the virtues. But faith is numbered among the gratuitous graces (1 Cor. 12:9) and likewise among the fruits (Gal. 5:23). Therefore faith is not a virtue.
On the contrary, Man is justified by the virtues, since "justice is all virtue," as the Philosopher states (Ethic. v, 1). Now man is justified by faith according to Rom. 5:1: "Being justified therefore by faith let us have peace," etc. Therefore faith is a virtue.
I answer that, As shown above, it is by human virtue that human acts are rendered good; hence, any habit that is always the principle of a good act, may be called a human virtue. Such a habit is living faith. For since to believe is an act of the intellect assenting to the truth at the command of the will, two things are required that this act may be perfect: one of which is that the intellect should infallibly tend to its object, which is the true; while the other is that the will should be infallibly directed to the last end, on account of which it assents to the true: and both of these are to be found in the act of living faith. For it belongs to the very essence of faith that the intellect should ever tend to the true, since nothing false can be the object of faith, as proved above (Q. 1, A. 3): while the effect of charity, which is the form of faith, is that the soul ever has its will directed to a good end. Therefore living faith is a virtue.
On the other hand, lifeless faith is not a virtue, because, though the act of lifeless faith is duly perfect on the part of the intellect, it has not its due perfection as regards the will: just as if temperance be in the concupiscible, without prudence being in the rational part, temperance is not a virtue, as stated above (I-II, Q. 65, A. 1), because the act of temperance requires both an act of reason, and an act of the concupiscible faculty, even as the act of faith requires an act of the will, and an act of the intellect.