We proceed to the fourth article thus:
1. It seems that unformed faith cannot become formed, nor formed faith unformed. It is said in I Cor.13:10: "when that which is perfect is come, then that which is in part shall be done away." Now in comparison with formed faith, unformed faith is imperfect. It will therefore be done away when formed faith is come. It follows that it cannot be numerically one habit with formed faith.
2. Again, the dead does not become the living. Unformed faith is dead, according to James 2:20: "faith without works is dead." It follows that unformed faith cannot become formed.
3. Again, when God's grace is bestowed on a believer, its effect is not less than when it is bestowed on an unbeliever. Now it causes a habit of faith in an unbeliever. It must therefore cause another habit of faith in a believer, who already has the habit of unformed faith.
4. Again, as Boethius says, "accidents cannot be altered." Faith is an accident. It follows that the same faith cannot be formed at one time and unformed at another.
On the other hand: a gloss on James 2:20, "faith without works is dead," says: "by works it is revived." Thus faith which was once dead and unformed becomes formed and living.
I answer: opinion has varied on this matter. Some have said that the habit of formed faith is not the same habit as that of unformed faith; that unformed faith is done away when formed faith comes; and similarly that when a man whose faith is formed sins mortally, God infuses another habit of unformed faith. But it does not seem possible that a gift of grace should expel another gift of God, nor that any gift of God should be infused in consequence of mortal sin. Others have said that although the habits of formed and unformed faith are different habits, the habit of unformed faith is not done away, but remains together with the habit of formed faith in the same person. But it seems no less impossible that the habit of unformed faith should remain, inactive, in one who has faith that is formed.
We must therefore say, as against such views, that the habit of formed and of unformed faith is the same habit. The reason for this is that a habit is differentiated by what belongs to it essentially. What pertains to the intellect belongs to faith essentially, since faith is a perfection of the intellect. But what pertains to the will does not belong to faith essentially, and cannot therefore justify a distinction within it. Now the distinction between formed and unformed faith depends on charity, which pertains to the will, not on anything which pertains to the intellect. Hence formed and unformed faith are not different habits.
On the first point: the apostle means that when imperfection is essential to the nature of that which is imperfect, that which is imperfect shall be done away when that which is perfect is come. For example, when open vision is come, faith shall be done away, which is essentially "of things not seen." But when imperfection is not essential to the nature of that which is imperfect, that which was imperfect and becomes perfect is numerically the same. For example, it is numerically the same person who was a boy and becomes a man, since boyhood is not essential to the nature of manhood. The unformed condition of faith is not essential to faith itself, but is accidental to it, as we have said. Hence it is the same faith which was unformed and becomes formed.
On the second point: what makes an animal alive belongs to its essence, since it is its essential form, namely, the soul. It is for this reason that the dead cannot become the living, and that the dead and the living differ in kind. But what brings faith to its form, or makes it alive, does not belong to the essence of faith. The two cannot then be compared.
On the third point: grace causes faith so long as faith endures, not only when it is newly begun in a man. For God works a man's justification continually, as we said in Pt. I, Q.104, Art.1, and 12ae, Q.109, Art.9, just as the sun continually illumines the atmosphere. Hence grace does not do less for the believer than for the unbeliever, since it causes faith in both. It confirms and perfects faith in the one, and creates it anew in the other. Or we might say that it is accidental, as due to the nature of the subject, that grace does not cause faith to arise in one who already has faith; just as it is accidental, conversely, that a second mortal sin does not deprive a man of grace if he has already lost it through a previous mortal sin.
On the fourth point: when formed faith becomes unformed, it is not faith itself that is altered, but the subject of faith, that is, the soul, which at one time has faith with charity, at another faith without charity.