I'd like to expand on something I recently said regarding Molinism. Molinism attempts to harmonize freewill with determinism. A possible world has a complete history. Even if that history is, in part, the result of choices made by libertarian agents, a possible world is a completed totality. The history of everything that happened in that world. A static, abstract object.
Let's say God instantiates a possible world. Let's say the A-theory is true. Let's say that in the actual world, the future is open. There is nothing in the actual world that causes the future to unfold in a particular direction.
Yet what is future vis-a-vis the actual world is past vis-a-vis the possible world. In effect, the future is past, because everything that will happen in the actual world exactly corresponds to everything that happened in the possible world. For God instantiates that particular history. What happened in that possible world.
Even though the future is open, future outcomes are equivalent to the accidental necessity of the past. Nothing can happen in the actual world that didn't happen in the possible world which it exemplifies. Nothing can happen in the actual world contrary to the possible world it exemplifies. As the mirror image of a possible world, nothing can turn out otherwise. So the future might as well lie in the past.
As I said before, if a possible world is indeterministic, an actual world is deterministic–like instant replay. Even if the original outcome was indeterminate, the playback is determinate.
Now, as a Calvinist, I don't think possible world histories are even partly the product of libertarian agents. But supposing we grant that contention for the sake of argument, if the actual world exemplifies the plot of a possible world, then it must mirror everything that happened in the possible world. It can never deviate from that blueprint.