I have some sympathy with the idea that the future does not exist and thus it is not knowable in principle, an omniscient being would only be able to know potential future states. Of course, if God experiences time, it is hard to claim that he does not change, because the contents of God's experience would change. However, I do think there is a difference in claiming that God changes in terms of the content of his experience and the idea of change that was classically opposed. Even process theology rejects the idea that God's character changes in any way, it is rather that God prehends the process of the world and "responds" according to that and God's character. In that view, the future does not exist. However, it would be wrong to say that the past is gone, the past partially constitutes the present and the potentials for the future.
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