I must give you another concept which we find in Thomas Aquinas, namely the concept of predestination. Here we have a cross-working of motives. Predestination is an Augustinian idea taken over by the Dominican Thomas Aquinas, on the basis of his principle of intellect, which understands the necessities, and can by necessity derive consequences from what has preceded. On the other hand the Augustinians, the Franciscans, especially under Duns Scotus’ influence, emphasized the will so much that Divine as well as human will became ultimate realities, became, so to speak, ontological ultimates, not determined by anything other than by themselves.

So they introduced the element of freedom – the Pelagian element. The Augustinians introduced a crypto- Pelagianism into medieval theology, I. e., a Pelagianism which is not an open but a hidden Pelagianism, while Thomas Aquinas on the basis of his intellectualism thought in deterministic terms. This is important because it shows that Thomas Aquinas was religiously much more powerful than the Protestant criticism of the Scholastic theology admits. It seems that Luther didn’t know Thomas Aquinas at all. He knew the late nominalistic theologians, of whom one can rightly say that they were distortions of Scholasticism, and he fought against them. But he could have found in Thomas Aquinas his own and Calvin’s predestinarian thinking.

We must stop now, unfortunately. I must say something next time about Thomistic ethics because they are so much in the foreground of present-day discussions that we cannot leave them out completely.
Paul Tillich, A History Of Christian Thought – Table of Contents