Here’s a thought I came up with recently, thanks in part to a post by Pruss here. Protestants of the classically reformed persuasion often say that mankind is totally depraved, and in the absence of Grace is entirely unable to avoid sinning mortally. According to the Catholic faith, it is certainly true that, in the absence of Grace, one cannot possibly freely choose the good, and this is reflected in the canons of the second council of Orange, and of course more strongly in the canons of Trent – this doesn’t amount to the strong doctrine of total depravity though, which Catholicism would deny even concerning demons. However, it seems to me that there is a specialized sense in which man without Grace can avoid some mortal sins.
Imagine that in some logically possible world w, at some time t1 I do commit a mortal sin of some kind. However, in a relevantly similar logically possible world w*, at the same time t1*, it never occurs to me to consider doing that particular mortal sin which I do commit in w. Thus, in w*, I am not presented existentially with the choice, simply because it doesn’t occur to me at all. In that case, of course, I would fail to commit the mortal sin which it is logically possible for me to have committed at that time, and yet it seems I would not have needed Grace in order to avoid sinning, since the occasion of choice with respect to the sin in question never arose in w*.
I think the only objection to this might be that, were I not to have even considered committing the mortal sin in question in w*, that itself would be the result of Grace delivering me from the near occasion of sin. Something tells me that isn’t properly the function of Grace, however – rather Grace is operative in order to enable me to choose the good when the option presents itself.