It should now be obvious that, in spite of his agnosticism, Aquinas has plenty to say about what we need to affirm of God from a philosohical viewpoint and without explicit reference to, or dependence on, Christian revelation. According to him, we have good philosophical grounds for saying that God is the creator of the world ex nihilo. He also thinks that there are philosophical reasons for believing that God is perfect, good, ubiquitous, eternal, unique, powerful, and knowledgeable.
But people who believe in God usually want to assert more of him that this. Pious Christians who plan for the future say that they shall do such and such 'God willing'. They think of God as having will. As a Christian, Aquinas certainly agrees with them, but does he think that their position is philosophically defensible? Does he believe that there are philosophical grounds for ascribing will to God? And does he think the same of the equally prevalent belief that God rules the world with justice and mercy? The God of the Bible is said to be just and merciful. And Aquinas believes in the God of the Bible. But does he hold that there are extra-biblical reasons for ascribing justice and mercy to God?
The short answer is 'Yes', and in this chapter we shall see why. The thoroughly systematic nature of Aquinas's thinking should by now be apparent to the reader. But we have further evidence of it as we turn now to his philosophical treatment of God's will, love, justice, and mercy, for what he has to say presupposes and connects with much that he teaches concerning God's changelessness, power, and knowledge. His philosophical case for ascribing will to God rests, for example, on his view of God's knowledge or understanding. And he develops it by drawing on the conclusion that God is wholly immutable.