Gratia non tollit naturam, sed perficit — Grace does not destroy nature, but perfects it. Grace perfects the totality of human nature—intellect, will, and heart. It also perfects the various operations proper to each rational power. As such, it perfects freedom. For Augustine, there was a tension between grace and freedom that resulted from his understanding of both. Augustine thought that one was first made righteous by God, then does the good. The genesis of this belief is his interpretation of Romans 9, partiucialurly verses eleven through eighteen:
Yet, before the twins were born or had done anything good or bad—in order that God’s purpose in election might stand: not by works but by him who calls—she was told, “The older will serve the younger.” Just as it is written: “Jacob I loved, but Esau I hated.” What then shall we say? Is God unjust? Not at all! For he says to Moses, “I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.” It does not, therefore, depend on human desire or effort, but on God’s mercy. For Scripture says to Pharaoh: “I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth.” Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden.
Augustine’s reading led him to believe that there is not much that the human agent does in the process of salvation, but that it is entirely up to God whether or not one is saved. His interpretation of this passage easily lends itself to a Calvinistic determinism whereby human choices are not free in any meaningful sense. This view wouldn’t offer much motivation on the part of the person since God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden. On the Augustinian view, grace overpowers nature.
At the opposite end of the spectrum, Augustine’s rival, Pelagius, said that man can choose to do the good of his own free will, without divine assistance. On this view, nature does not need grace. The semi-pelagians attempted to reconcile Augustine and Pelagius by proposing that we still in some sense need grace, but that we can be the ones who earn God’s grace. Though grace can be merited, it certainly cannot be earned. It is not the case that if a human does x, then God will be obliged to give y amount of grace. God is not obliged to give you y grace if you do x, but you can merit y amount of grace. By this, we mean that God’s grace which is given in response to the person doing x is not earned like the semi-pelagianms say, but is merited. God did not owe that grace to the person, but gave it as a reward. So the attempted synthesis of the Semi-Pelagians fails since it still overemphasizes the role of human freedom.
Fast forward a few hundred years and we get to Anselm’s attempted synthesis of the two. Up to this point, an adequate reconciliation of Augustine and Pelagius had not been achieved at least in the west. How, if at all, can human freedom and divine grace be harmonized? Anselm argues that since original justice had been lost at the fall, our ability to choose the good has been tainted. This view can be conformed to Aquinas’ view that all human acts have some perceived good towards which the will directs itself since Anselm is not saying that the post-lapsarian will now desires evil, but that it does often orient itself to a lesser good. The will still chooses some perceived good, but not always the highest good. Saint Paul lays this out in Romans 7:15-25 when he speaks about doing the evil he does not desire to do. One doesn’t need to think very hard to imagine a time when this tension has affected them. We have the ability to choose the good and even have a knowledge of what the highest good is, yet, we still choose a lesser good.
Now comes the role of grace for Anselm. Far from being an obstacle to freedom, grace perfects it. Grace does this by making the decision t choose the highest good easier, and, at times, even pleasant. This makes one freer. Freedom, we must remember, is not merely the ability to choose between alternatives, but is the ability to flourish as the type of being one is. Therefore, since grace allows man to more easily choose the good conducive to his nature, the freer it makes him. Anselm’s synthesis masterfully avoids both the divine determinism of Augustine and the homocentrism of Pelagius. It says that God’s grace does not overpower us, but makes us who we were originally intended to be. Neither does it say that man alone can save himself, but that he can work out his salvation because of the free gift of grace. Thus we can say: gratia non tollit libertatem, sed perficit — grace does not destroy freedom, but perfects it.
So, a person who's by grace become perfectly free & fully rational, by definition, would not reject God.
This is consistent with this comment by DBH:
https://afkimel.wordpress.com/2019/09/24/the-possibility-of-a-thomistic-universalism-a-review-of-david-bentley-harts-that-all-shall-be-saved/#comment-27383
Splendid reflection.
For further reading, my friend, Tom Belt: https://anopenorthodoxy.wordpress.com/tag/divine-freedom/