The goal of this paper is to show that Thomas Aquinas, in his _Disputed Questions on Evil_, presents a theory of free will that is compatibilist but still involves a version of the principle of alternative possibilities (PAP) and even requires alternative possibilities for a certain kind of responsibility. In Aquinas’ view, choosing between possibilities is not the primary power of the will. Rather, choice arises through the complex interaction of various parts of human psychology, in particular through the indeterminacy (...) of the intellect and through the interaction between reason and passion. Both of these ways provide cases where Aquinas not only allows for alternative possibilities but thinks that they are necessary for moral responsibility, all the while remaining, strictly speaking, a compatibilist. (shrink)