Key quote: Isaiah (1:18): “If your sins be as scarlet, they shall be made as white as snow”.
1 From these considerations it is apparent that man, even if he does not persevere but falls into sin, may be restored to the good by the help of grace.
2 Indeed, it pertains to the same power to maintain the continued salvation of a person and to restore it when it has been interrupted, just as health is continually maintained by natural power in the body, and an interruption of health is repaired by that same natural power. Now, man perseveres in the good by means of divine grace, as we showed. Therefore, if one has fallen as a result of sin, he may be restored by means of the same grace.
3 Again, an agent that does not require a disposition in its subject can impress its effect on the subject, no matter how the subject be disposed. For this reason, God, Who does not require a subject that is disposed for His action, can produce a natural form without a disposition of the subject; for example, when He enlightens the blind, revives the dead, and so on for similar cases. But, just as He requires no natural disposition in a corporeal subject, He does not need merit in the will in order to grant grace, for it is given without there being any merits, as we showed. Therefore, God can grant a person sanctifying grace, through which sins are removed, even after he has fallen from grace by sin.
Notes Think of requiring a disposition in its subject as having the power to make a cause. You have the power of motion; you do not have the power to turn water into wine in an instant. That requires the ability to change the essence of a thing.
4 Besides, the only things that man cannot recover when they are lost are those which come to him through generation, such as his natural potencies and organs, and the reason for this is that man cannot be generated a second time. Now, the help of grace is not given man through generation, but after he already exists. Therefore, he can again be restored in order to destroy sin after the loss of grace.
5 Moreover, grace is a habitual disposition in the soul, as we showed. But habits that are acquired by activity, if lost, can again be acquired through the acts suitable for their acquisition. So, it is much more likely that, if it be lost, grace uniting one to God and freeing one from sin can be restored by divine working.
6 Furthermore, among the works of God, none is futile, as none is futile among the works of nature, for nature gets this characteristic from God. Now, it would be futile for something to be moved if it could not reach the end of its motion. It must be, then, that what is naturally moved toward an end is able to come to that end. But, after man has fallen into sin, for as long as he continues in the present state of life, there remains in him an aptitude to be moved toward the good. The signs of this are the desire for the good and sorrow for evil which still continue in man after sin. So, it is possible for man to again return after sin to the good which grace works in man.
Notes Never surrender.
7 Again, no passive Potency is found in the nature of things which cannot be reduced to act by some natural active potency. Much less, then, is it possible for there to be a potency in the human soul which is not reducible to act by divine active potency. But there remains in the human soul, even after sin, a potency toward the good; for the natural potencies are not removed by sin, and by means of them the soul is directed toward its good. So, it can be restored to the good by divine potency. Thus, man can obtain the remission of sins by means of grace.
8 Hence, it is said in Isaiah (1:18): “If your sins be as scarlet, they shall be made as white as snow”; and in Proverbs (10:12): “charity covers all sins.” This, too, we ask daily of the Lord, and not in vain, for we say: “Forgive us our trespasses.”
9 By this we set aside the error of the Novatians, who said that man could not obtain pardon for sins which he commits after baptism.