I recently picked up Eleonore Stump's massive Aquinas from the library. I haven't really started reading it, but I've dipped into it. I was startled to find her claiming that "Aquinas does not suppose that human freedomeven as regards willing consists in or depends on the ability to do otherwise" (p. 299). A bit surprising, I thought, given that Aquinas says, at ST 2-1.13.6, "For man can will and not will, act and not act; again, he can will this or that, and do this or that," and this is intended to be a clarification of why we do not will necessarily. So what does she mean?
Aquinas distinguishes between two sorts of necessity: a "necessity of coercion" and a "necessity of natural inclination." The first is incompatible with free choice. The second, however, Aquinas says is not incompatible with it. It is from this that she draws the conclusion that Aquinas rejects the principle of alternative possibilities, where it is defined as
(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.
But surely Stump is incorrect in this regard. Aquinas holds not that we are sometimes moved by a necessity of natural inclination and sometimes not, but that we are always moved b a necessity of natural inclination. The will consists in inclination to good in general; this is the natural movement of the will, and it therefore necessarily is inclined to good in general. The reason this does not introduce any "necessity of coercion" is that the good in general is precisely that: general. As an end it does not determine us to any particular good but instead makes it possible for us to choose any particular good that falls within itself (see here, for instance). The reason that necessity of natural inclination does not conflict with free choice is that it is the necessary precondition for any choice whatsoever. Necessity of natural inclination, therefore, does not in any way interfere with PAP. And, indeed, Aquinas insists that our wills are not necessitated to one thing, and, indeed, not necessitated to anything except in the case of natural inclination (see here). When the saints see God face to face, they will love Him (as supreme good) by necessity of natural inclination, and will not be able to will evil; but they will still be free to express their love for God in many different ways, which is why Aquinas can say (in a De Malo passage cited by Stump, and also, I think, in an SCG passage I can't remember or find right now) that there is no state in which humans lack liberum arbitrium, what I have been calling 'free choice'.
I conclude that Stump is incorrect to say that "on Aquinas's account, human freedom even with regard to willing does not depend on her having alternative possibilities available to her; it is possible for an agent to act freely even when she cannot act otherwise than she does" (p. 300).
