...nothing in Aquinas's theory of free will requires a free will to be able to choose evil over good. The principle much defended by some contemporary philosophers that a person acts with free will and moral responsibility only in case he could have done otherwise than he did is therefore not a principle Aquinas espouses. (Stump, Aquinas, p. 106)
This appears to play a role in Stump's argument in the passage I've been chewing on: "Although the blessed cannot will evil, they nonetheless will freely whatever good they will" (p. 299).
What puzzles me is why she thinks this is so. PAP, or the principle of alternative possibilities, if you recall, is this:
(PAP) A person has free will with regard to (or is morally responsible for) an action A only if he could have done otherwise than A.
In the case of God or the blessed, who cannot sin, the idea (I presume) is that they cannot do (or will) otherwise than impeccably; so that if PAP were true, they would not freely be doing A (and would not be morally responsible for it). At least, this is the only thing I can think of that would lead to this conclusion.
But this doesn't seem to me to be right (and this is the disagreement over PAP that I mentioned earlier). For consider God doing A; God could instead do B. Both A and B are necessarily good; God cannot do otherwise than actions like A or B. But it is still the case that for any good action A, God could have done otherwise; and for any good action B, God could have done otherwise. So for any good action A or B, God could have done otherwise and there is therefore nothing in this situation to tell against PAP's application. As with God, so a fortiori with the saints; and as with the saints, so a fortiori with everyone else. (This isn't, as far as I can unravel it, the entire argument presented by Stump; she has another line of argumentation on the issue of intellect/will interaction and on being overcome with passion; I think it can be shown that neither of these affects PAP in the sense suggested here, but that's an argument for another day.)
Because I'm completely unimpressed by the contortions of Frankfurt-style counterexamples, I don't keep a close eye on the Frankfurt-style counterexample literature, in which these issues are usually discussed. Are there actually defenders of PAP who insist that it means that if we cannot will evil we cannot be responsible for good actions, even if we could do other good actions? Could she perhaps be thinking of certain variants of the Free Will Defense, in which God is said to have created people capable of willing evil because that follows from creating people capable of willing freely? If this is so, I think I agree that Aquinas has to rule out such a strategy, at least in a simple form; but this does not mean he has proposed anything that would require rejecting PAP.
