Here is an argument against Actus Purus.
- If God is actus purus then he can contain no potentiality at all.
- The Christian God knows the free choices of creatures.
- Free choices can be other than they are.
- Therefore God’s knowledge contains potential to be other than it is.
- Ergo God contains potentiality, and so cannot be pure act.
If God ever experiences something in his being “because” of what creation does, then he cannot pure act. This is because, by responding to what we do God is actualizing some state of affairs that would not have come about but for our action, and this means that God, apart from our so acting, or supposing we were to act differently, would not have actualized the state of affairs that he in fact did actualize.
Consider, for example, the Incarnation. If we had not sinned, Christ would not have been crucified. Thus, the fact that God assumed human flesh and was crucified – which was certainly an act of God – proves that God had the potential to become human and be crucified supposing we sin. The important point here is this “supposing.” For it means that something about God’s very being came to be which would not have come to be if we had not sinned. And if we are free then it was certainly possible for us to have not sinned.
Consider another example. If God has knowledge of our free actions, he either knows these things because we do them, or we do them because he knows them. However, if God’s knowledge is the cause of our actions, then we are not free to do other than God’s pre-conceived knowledge of what we will do. But if God knows what we do because we do it (which is what all free will theists believe) then God is conditioned and has potentiality with regard to his knowledge. For, supposing we do or act otherwise, God’s knowledge would be different than it is.
Both these arguments, by the way, work just the same if God is eternal and existing in a simultaneous now. For even if you reduce all times to a present, God still has knowledge of the present either because the present exists and so imposes knowledge onto God, or because God’s knowledge itself imposes form and structure onto the present. In other words God is either eternally and presently receiving knowledge of the free creation (which implies him being in an eternal state of potentiality), or he eternally and presently causes what the free creation will be. (Since this causing entails determinism and makes God the author of evil, contradicts our existential experience, and robs us of all moral responsibility, it seems we should not hold it.)
I can well imagine a sort of immovable, changeless substance that is the same in all possible worlds; and I can well imagine us being asymmetrically related to that substance differently based on what we do. When one steps from standing in the sunlight to standing in the shade the sun itself doesn’t change, even though the warmth it gives to our bodies does. But I cannot imagine that such a substance could be a personal being. The Biblical God – manifested in Christ – wills and knows things about his creation. But if this is really true, what God wills and knows is therefore in some way dependent upon beings outside his own self act. If knowledge is an essential part of God’s being (which it must be if he is a person) and if God knows us contingent creatures, then how can God be the actus purus described by Aquinas? For that being is totally unconditioned by the creation – indeed he literally cannot be conditioned by anything outside himself, since that would imply passivity. If God is actus purus then none of his inner being can have reference or relation to things outside his own self, since by virtue of the fact that these “non-God” things would draw forth such states from God and would cause him to be conditioned. On such a view, how could God create, since that would require him to stand in his own being as a CREATOR in relation to what he has made?
It is too little mentioned that Aristotle’s God could neither know the world nor create it. Aristotle saw that the logic of his doctrine of acutus purus entailed these as necessary consequences. But Aristotle was not a Christian. He did not believe God was Father, nor that God’s Son became man, nor that God made the universe ex nihilo. So while perhaps he can be forgiven for such a impersonal conception of the divine, can we Christians? If we believe that God is some metaphysical force, some pure actuality, some abstract notion of being itself, how is it logically possible to believe he also created the universe, knows its contingencies, and entered into it as man?