A Roman Catholic once told me he believed that salvation was by grace, because doing good works is only possible because God makes it possible. God is the ground of our being. So even though works are part of the condition of salvation, salvation is by “grace” because the fact that we exist at all is thanks to God.
Basically, he was engaged in metaphysical thinking.
He was defining “grace” in a metaphysical way.
What is metaphysics?
It’s hard to define. It was an ancient form of science, but was gradually replaced by the natural sciences. Nowadays we consider it a part of philosophy, the branch that studies existence as such. So while natural sciences like zoology studies animals, geology studies the earth, astronomy studies the stars, pathology studies diseases, and so on, metaphysics studies how anything can exist at all.
The natural sciences study beings.
Metaphysics studies Being.
Medieval philosophy—which was a deeply religious philosophy—tried to reconcile the philosophies of Plato and Aristotle with Christian doctrine. One of the things they concluded was that all creaturely existence was said to depend upon the Creator. Whereas God exists necessarily, we exist contingently, because God wills that we do. He keeps us in existence. Without God—poof!—we would disappear.
Basically, my Catholic friend was saying that, since God created us out of the good pleasure of His will, and our moment-to-moment existence depends on Him, everything we do, including our works, ultimately depends on God granting us existence. And that’s “grace.” So even though my Catholic friend was adamant that works are a condition of salvation (by misinterpreting James 2), since we could not do any works unless God kept us in existence, he said that salvation was by “grace.”
Well, it’s a nice theory, and he is free to use whatever terms he wants, however he wants, but his meaning of “grace” was not the NT meaning of “grace,” still less Paul’s meaning grace.
When the NT says that we are saved by “grace,” it is not making a metaphysical statement about the contingency of our existence! The NT, especially Paul, means that salvation is by “grace” because it is by faith, apart from works.
For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast (Ephesians 2:8-9).
Do you see that “grace” is contrasted with “works”? They’re like oil and water: they can’t be mixed!
The faith-way of salvation is the grace-way.
The works-way of salvation is the antithesis of the grace-way.
Here is Paul again:
But if it is by grace, it is no longer on the basis of works, otherwise grace is no longer grace (Romans 11:6).
Again, “grace” is defined as “no longer on the basis of works.” You add works into the salvation equation and “grace is no longer grace.”
The point is, don’t get confused when someone starts talking about “grace” in a metaphysical way. “Don’t let anyone capture you with empty philosophies and high-sounding nonsense,” Paul warned (Colossians 2:8). That’s still true.
Quit the metaphysical thinking, and stick to the Pauline sense of “grace.” Grace is not a metaphysical statement about the contingency of our existence, but God’s mental attitude of favor towards us, whereby He offers us eternal life by faith in Jesus, apart from our works.
 I did my Master’s Thesis on Alvin Plantinga and Thomas Aquinas, so I know a little about metaphysics. I find the subject fascinating. I like studying it as a piece of intellectual history. But I would be among those who think metaphysics should be, and eventually will be, replaced by the natural sciences. And I definitely believe that Biblical theology needs to be aware of when and how metaphysics has altered our perception of the Biblical text. Traditional views of salvation are often metaphysical, not Biblical (e.g., the doctrines of original sin, recapitulation, and theosis, to name only three).