A simple, and calm argument this week, and as far as I can tell, without controversy.
1 Man also needs the help of divine grace so that he may persevere in the good.
2 Indeed, everything that is variable in itself needs the help of an immovable mover so that it may be fixed on one objective. But man is subject to variation, both from evil to good and from good to evil. So, in order that he may immovably continue in the good, which is to persevere, he needs divine help.
3 Again, for that which surpasses the powers of free choice, man needs the help of divine grace. But the power of free choice does not extend to the effect of final perseverance in the good. This is evident as follows. In fact, the power of free choice applies to those things which fall within the scope of election.
Now, what is chosen is some particular operation that can be performed. But such a particular operation is what is here and now present. Hence, that which falls under the power of free choice is something that is to be done now. But to persevere does not mean something as now operable, but the continuation of an operation throughout time. Now, this effect, of persevering in the good, is beyond the power of free choice. Therefore, man needs the help of divine grace to persevere in the good.
4 Besides, though man is the master of his action through will and free choice, he is not the master of his natural powers. So, while he is free to will or not to will something, he cannot by willing produce such a result that his will, by the very fact of willing, would be immovably fixed on what be wills or chooses. But this is what is required for perseverance; that is, the will must endure immovably in the good. So, perseverance is not within the scope of free choice. Therefore, the help of divine grace must be available to man so that he may persevere.
5 Moreover, suppose that there are several agents in succession, such that one of them acts after the action of another: the continuation of the action of these agents cannot be caused by any one of them, for no one of them acts forever; nor can it be caused by all of them, since they do not act together. Consequently, the continuity must be caused by some higher agent that always acts, just as the Philosopher proves, in Physics VIII, that the continuity of the generative process in animals is caused by some higher, external agent.
Now, let us suppose the case of someone who is persevering in the good. There are, then, in his case many movements of free choice tending toward the good, successively following each other up to the end. So, for this continuation in the good, which is perseverance, no one of these movements can be the cause, since none of them lasts forever. Nor can all of them together, for they are not together, and so they cannot cause something together. It remains, then, that this continuation is caused by some higher being. Therefore, man needs the help of higher grace to persevere in the good.
6 Furthermore, if many things are ordered to one end, their entire order until they reach the end comes from the first agent directing them to the end. Now, in the case of a man who perseveres in the good there are many movements and many actions reaching to the end. So, the entire order of these movements and actions must be caused by the first agent directing them to the end. But we showed that they are directed by the help of divine grace to the ultimate end. Therefore, the entire order and continuity of good works, in him who perseveres in the good, is due to the help of divine grace.
7 Hence, it is said to the Philippians (1:6): “He who hath begun a good work in you will perfect it unto the day of Christ Jesus”; and in 1 Peter (5:10): “the God of all grace, Who has called us to His eternal glory… after you have suffered a little, will Himself perfect you and confirm you and establish you.”
8 There are also found in Sacred Scripture many prayers in which perseverance is sought from God: thus, in the Psalm (16:5): “Perfect You my goings in Your paths, that my footsteps be not moved”; and in 2 Thessalonians (2:15-16): “May God, our Father, exhort your hearts and confirm you in every work and word.” This is also what is asked in the Lord’s Prayer, especially when one says, “Your kingdom come”; indeed, the kingdom of God will not come for us unless we have persevered in the good. Now it would be ridiculous to ask something from God if He were not the giver of it. So, man’s perseverance is from God.
9 By this we set aside the error of the Pelagians, who said that free choice is sufficient for man to persevere in the good, and that he does not need the help of grace for this purpose.
Notes Put simply, the chance for mistake is too great.
10 However, we should note that even he who possesses grace asks God that he may persevere in the good. just as free choice is not sufficient without the external help of God, for this effect of persevering in the good, so neither is a habit infused in us enough for this purpose. For habits that are divinely infused in us during the present state of life do not take away entirely from free choice the possibility of being moved toward evil, even though free choice is somewhat fixed in the good by means of them.
And so, when we say that man needs the help of grace to persevere unto the end, we do not understand that, in addition to habitual grace previously infused to assure good operation, another must further be infused for persevering; what we do understand is that, once possessed of all the gratuitous habits, a man still needs the help of divine providence externally governing him.