Divine Foreknowledge and Free Will: A Question About the Possibility of Choosing Otherwise

I have been thinking about the relationship between divine foreknowledge and free will, particularly after looking into the responses given by philosophers such as Boethius and Thomas Aquinas.

Suppose that a person is faced with two possibilities: choosing A or choosing B. God, being omniscient, eternally knows which choice the person will make. If God infallibly knows that the person will choose A, then A will happen. After all, if the person were to choose B, God’s knowledge would turn out to be false, which is impossible.

At first, this does not necessarily seem to be a causal problem. God’s knowledge does not have to be what causes the choice. The difficulty is something else: if God eternally knows that A will happen, in what sense could the person genuinely have chosen B instead? There seems to be an important distinction between saying that A is certain and saying that A is necessary. If A is certain because God knows that A will happen, does that merely mean that God cannot be mistaken? Or does it also mean that A could not have been otherwise?

This distinction seems to be crucial. If A is necessary in the sense that B was never genuinely possible, then it seems difficult to say that the person could freely have chosen B. On the other hand, if B really was possible, I want to understand how that possibility can exist when it is already an eternal and infallible truth that the person will choose A.

Thomas Aquinas offers an important response to this problem. God does not know future events in the same way that we do, waiting for them to occur. Because God is eternal, He knows all moments without being subject to temporal succession. Therefore, His knowledge does not necessarily turn a contingent event into a necessary one.

But I still have a question about this solution. If we say, “If the person had chosen B, God would eternally have known that they would choose B,” does that actually explain why B was a genuine possibility? Or are we simply describing what God’s knowledge would have been if a different event had occurred? Perhaps I am misunderstanding the relationship between certainty, necessity, and possibility. Perhaps the real issue lies in what we mean when we say that someone “could have chosen otherwise.”

So my question is: If God infallibly knows, from eternity, that a person will choose A, in what sense could that person genuinely have chosen B instead?

I am not trying to argue for a particular conclusion. I would mainly like to understand whether there is a mistake in this line of reasoning, and how different philosophical positions respond to it.