As many times as I've heard or read James 2:14, I didn't really notice that little "that" until this past Sunday at Mass:
What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him?
I've always read James from the perspective of The Great Faith v. Works Debate, and not given it much thought, since the Catholic position of "both/and" (to put it crudely) always made perfect sense to me.
But of course what I know as The Great Faith v. Works Debate did not arise until the Sixteenth Century, so that can't have been the context in which St. James was writing. And in verse 14, James doesn't ask, "Can faith alone save him?", but, "Can that faith save him?"
"That faith": among all possible faiths, the faith that does not produce works. I don't think he is saying we need to add works to our faith, as though salvation were due to an additive combination of that univocal thing Faith and that univocal thing Works. Rather, he is saying that there are two different faiths. When he writes, in verse 18:
Demonstrate your faith to me without works, and I will demonstrate my faith to you from my works.
The "your faith" and the "my faith" are not the same faith. Verse 26 caps it off:
For just as a body without a spirit is dead, so also faith without works is dead.
Note that a body without a spirit is literally substantially different from a body with a spirit. A human being is not the additive combinations of a corpse plus a soul. Similarly, the dead faith lacking works is substantially different from the living faith with works.
And all from finally noticing the little word "that." (Which, incidentally, is missing from the King James Version and the Douay Rheims.)