We proceed to the ninth article thus:

1. It seems that a man can merit perseverance. For a man in grace can merit what he obtains through petition, and men obtain perseverance through petition, since otherwise perseverance would be asked of God in vain by the petition of the Lord's prayer, as Augustine says (2 De Bono Persev.). [47] It follows that perseverance can be merited by a man in grace.

2. Again, to be unable to sin is more than not to sin. Now to be unable to sin can be merited, since one merits eternal life, which is by its very nature impeccable. Much more, then, can one merit to live without sin, that is, to persevere.

3. Again, an increase of grace is more than perseverance in the grace which one already possesses. Now it was said in the preceding article that a man can merit an increase of grace. Much more, then, can he merit perseverance in the grace which he already possesses.

On the other hand: unless sin prevents it, a man receives from God everything that he merits. Now many who perform works of merit do not receive perseverance. But we cannot attribute this to sin, since God would not allow anyone who merited perseverance to fall into sin, for the very reason that sin is opposed to perseverance. It follows that perseverance cannot be merited.

I answer: since the free will with which he is naturally endowed can turn either to good or to evil, there are two ways in which a man may obtain from God perseverance in good. He may obtain it through the consummation of grace whereby his will is finally turned to good, as it shall be in heaven. He may also obtain it through a divine moving which inclines him to good till the end. Now as we explained in Arts.6, 7, and 8, a man merits what is related to the movement of his free will as the final term to which God's moving directs it. But he does not merit what is related to the movement of his free will as its principle. This makes it clear that the perseverance which belongs to glory is merited, since it is the final term of the movement of man's free will. But the perseverance of the wayfarer is not merited, since it depends entirely on the moving of God, which is the principle of all merit. God nevertheless bestows the gift of perseverance freely, on whomsoever he bestows it.

On the first point: through petitionary prayer we receive many things which we do not merit. For God hears even the prayers of sinners who ask for the forgiveness which they do not deserve, as Augustine says {Tract.44 in Joan.) on John 9:31: "we know that God heareth not sinners." Were it not so, the publican would have said in vain: "God be merciful to me a sinner." So also may one obtain the gift of perseverance through asking it of God, either for oneself or for another, even though it cannot be merited.

On the second point: the perseverance which belongs to glory is related to the meritorious actions of the free will as their final term. But the perseverance of the wayfarer is not so related to them, as we have said. The third point concerning the increase of grace is similarly answered, as will be clear from this and the preceding article.

[47] Cf. De Corrept. et Gratia, 6, 10. The petition referred to is "Hallowed be thy name."