The following appeared in the comments section on a blog in answer to the question of whether prayer “changes God’s mind.”

If God could change His mind, then He would be learning from and therefore be dependent upon His own creation.  He would be growing from good to better, from wise to wiser.  He would in short be deprived of some of the essential characteristics of Deity – His Omniscience and Timelessness.

The writer was a Calvinist, but I have heard Thomists (of which I am one) make similar kinds of statements. While I do not believe that creatures can make God “change his mind,” I have always been troubled by the more sophisticated metaphysical assertion that really lies behind the claim — that God in no way responds to creatures, and that contingent actions of creatures do not make any difference to God’s knowledge. If they did, God would depend on creatures for that knowledge, and God’s would change, either for the better or the worst, etc. While this position is common among Calvinists and Banezian Thomists, I do not believe it is Thomas’s own position, and I find it problematic because it inevitably leads to determinism–a position Thomas rejects.

I replied as follows:

There are some metaphysical assertions here, some of which I would agree with, some of which I think need clarification, and some of which I would deny.

1) I agree that God does not “change his mind.”
2) I agree that God cannot grow or change either from good to better or from better to worse.
3) God is, in the words of St. Thomas, purus actus essendi—the pure act of fullness of self-existence. This means that God exists necessarily, that he is infinite, that his being is fully actualized, and cannot be improved, added to or diminished.
4) At the same time, God is absolutely free. God can choose to create or not create. God might not have created any universe at all, and, if so, there would be no less being or less goodness than if God had created.
5) Any universe that God creates will be contingent, but contingency has more than one meaning. So first, any universe that God can create will be a contingent universe in the sense that it might or might not exist.
6) But God can also create a contingent universe in the sense that he can create an infinity of different kinds of universes. So, contrary to Leibniz, there is no best of all possible world. Of any universe that God creates, he could also create a better one. Since everything except God is by definition finite, any universe can contain more or less perfection and more or less being. Thus any finite universe can also be improved on or made better.
7) However, if God is omnipotent, then God can also create a universe that is contingent in the sense that it contains genuinely contingent events, events that might or might not happen. If God is free to act or not to act, to create or not to create, to create one universe rather than another, then God is also free to create a universe in which creatures are free to act or not to act, to do one thing rather than another. If God is the chief actor or agent in the universe, then God is also free to create genuine finite agents, contingent beings that can act in such a manner that their actions are not determined. To deny that God can do this is itself to restrict God’s freedom. Theologians refer to this freedom as natural freedom. Thomas Aquinas, for instance, states that even after the fall, human beings are free to do things like build houses. My natural freedom includes the freedom to write a response in which I express my disagreement with carl. carl has the natural freedom to respond by saying that I have no such natural freedom.
8) It is important not to confuse natural freedom with voluntariness. Some advocates of determinism state that created events can be considered contingent in the sense that their agents act voluntarily, but not in the sense that the agent could act otherwise. But this is simply to deny that created agents are genuine agents.
9) One of the key examples of such contingency of created agents, of events that might be other, is sin. Scripture is clear that God does not will sin, deplores it, and forbids sin. If there is no such thing as natural freedom, then God forbids that which will necessarily happen anyway, and God’s command not to sin is in contradiction to the universe he has created.
10) If God creates a universe in which there are events that can be other, then God’s own freedom includes his ability to act differently in consequence of those events. Again, if sin is a contingent event, then it might not have happened. It was genuinely possible that the first human beings might not have disobeyed the divine command, and we would now live in an unfallen world. However, given that sin has occurred, God is free to act in more than one way in consequence. In his freedom, God could have left humanity in its sinful state. God also could choose to redeem humanity, and scripture tells us that God has chosen to redeem humanity from sin by becoming incarnate in Jesus Christ. So the incarnation is an event that itself is a consequence of a contingent created event that might or might not have happened. In short, the incarnation means that in God’s freedom, God can respond to human actions.
11) Thus, if God is genuinely free, then there are a number of possible created scenarios. God might not have created any world at all. God might have created a different world than the world God has created. God might have created a world in which there was no sin. God might have created a world in which sin existed, but God does not redeem. God might have created a world in which sin existed, but God does redeem.
12) Given these various possibilities of divine freedom, it is clear that both God’s will and knowledge have numerous (indeed infinite) possibilities, and whichever scenario God wills to bring into being, God’s knowledge will be other than if he had chosen to create a different reality. So God knows whether he will create or will not create a universe, and whichever choice God makes, God’s knowledge will be have a different content than if God had chosen otherwise. Such knowledge cannot mean that God changes in the sense that he attains more fullness or perfection of being, nor can it mean that he becomes better or worse. God is infinite and no created scenario can increase God’s infinite being. The infinite plus the finite is not greater than the infinite alone. God without a world is infinite perfection. God with a world is infinite perfection. Whatever finite world God creates or does not create, there will be differences in terms of finite perfection or being, however, there will be no difference in terms of God’s fullness of existence. Created contingencies do not add to or take away from God’s perfection.
13) I would conclude then that the objection is a red herring, and is itself a restriction of God’s freedom. Since any created possibility whatsoever entails a different content to God’s omniscient knowledge, and none entails more fullness of perfection of the Divine Being itself, a created universe in which genuinely contingent events exist (that could be otherwise, that might or might not happen) does not mean that God changes or becomes dependent on creation. That God genuinely answers prayer is no more problematic than that God is free to create or not to create, to create a world in which sin might or might not happen, to become incarnate or not to become incarnate.
14) The question of timelessness is another question, which would involve further detailed discussion. In short, I agree with Thomas that God is “timeless.” However, I also agree with Thomas that God’s “timelessnessness,” omniscience, and omnipotence, are compatible with created contingencies. Thomas summarizes the question correctly not by asking whether, given God’s immutability, timelessness, etc., there can be created contingencies, but, rather to the contrary, “whether God knows future contingents?” He argues that God does. At the same time, it is crucial to recognize that “time-less-ness” is not a positive attribute of God, but a negative one. “Time-less-ness” does not provide a positive description, but rather denies of God the temporal limitations entailed in moving from potency to act characteristic of physical creatures. However, to say that God is eternal does not give us a positive conception of God’s relation to time, nor does it deny that God’s knowledge will be other depending on various created scenarios. How could this not be the case if God knows future contingents? Time-less-ness does say in effect that God is “super-temporal,” but we do not know what that means.