Dreamer upon the board
There is an argument for saying that divine foreknowledge is incompatible with free will.
So let us argue with a story - place a dreamer upon the board and call her Protagonist, give her a grand destiny that she could choose or not to fulfil, and see what she does.
The dreamer considers, loiters in the celestial lobby of the universe, looking around, making up her mind. She listens to the whispers of the stars and the songs of the living and in time she hatches her Mad Plan, a plan that had been with her from the start but that was entirely up to her just what to actually do with it. Once decided, however, the plan is out, set in motion, for now it simply is: the plan is true, even if she still has almost no idea what the details might entail.
The gods know it. They must, according to the man outside the pastry shop who mutters at length about the apotheosis of cheese, for the Cheese God knows all, for the Cheese God must know all, for He is the Cheese God, among other gods. So if they do know it all, these gods, then they'll have known it all all along, because all includes the outcome of Protagonist's plan, and her destiny, and her dog, and even the rhino that ate the moon long before any of this began. All, really, is everything. It's all part of everything, and it always was.
So the gods will have known all along. Even before the dreamer Protagonist was placed upon the board, they knew. Before she made her plan and chose to step into the world proper and go through with it, they knew she would. But since they already knew, and they could not have been wrong, there could have been no possibility or choice for the dreamer to have not made the plan she did, for her to have not gone through with it, because then this would not have been what they had known. Indeed, because the plan effectively preceded her, it could not even be truly said to be her Mad Plan, but merely a plan that she enacted, pawn upon the board.
None of it was her choice, because she is not capable of affecting the past, and thus with divine foreknowledge there can be no free will.
Done is done, right?
She would say yes, done is done. But she is also no stranger to things not necessarily happening in order - done may be done, but that doesn't mean it's done when we think it is. Like she once said to me, "Objects shall fall upwards, perhaps? Effect precedes cause... but of course it does. I am standing on my head because you are about to dare me to do so. I trust you to be you."
Sense is out the window.
Or perhaps the assumptions are wrong.
Perhaps it is up to her what the gods have always known about what she would do. By her choosing it, they know, and have known it all along. Should she choose something else instead, the gods will have known that something else all along. Thus the dreamer, mortal though she may be, can indeed affect the past, a past that the gods then use to affect their futures to help or hinder as they will.
Perhaps the future is simply 'open'. Gods know everything there is to know, but they don't know the future for sure any more than the rest of us, because future is future and it just hasn't happened yet. Even the Cheese God himself, of pastry shop fame, knows not exactly what will happen, but He knows enough, more than enough - everything that can happen, every possibility, every thread in the intricate and infinite web of irreality, and even the thickness of each, which choice is most likely given all the preceding. But there is no specific knowledge of the future to affect in the past because the future simply doesn't work that way.
But each of these is based on an assumption as well - that time either flows or it doesn't. If it flows, then there is a future that can act as bright unknown, but past is good and past. If it doesn't, then canvas of the board is a whole lot more complicated, but there is room for effects preceding cause on such a board, and indeed perhaps far stranger seeming yet.
So what is time?
Those who study chaos dynamics could tell you that time depends on eigenstuff, which means something is involved - and something is involved in everything. Meantime these arguments here could fit either way. Free will could fit either way - maybe it isn't incompatible with divine foreknowledge, but it doesn't mean we necessarily have both, or either.
The dreamer, whose name is really Coraline, says of course there is free will - it's what keeps the universe from imploding in on itself. Were there not free will and a subsequent clash between a multitude of minds, that would mean the universe is in truth but a single mind - and a single mind would have gone too entirely mad to persist by now, holding pieces of madness like herself so securely in it.
Perhaps this is so, but I don't buy it. Why should there necessarily be free will at all? Regardless of one's view of time or how changeable past or future are, stuff happens. Subsequent stuff happens. Choices are made based on stuff that happened. And the story? It's just a way to drive us forward, but that doesn't mean it's meaningless, either. We may not be the original authors of our choices, but it doesn't make them not still our choices, or make them not affect us.
Or maybe the universe is just insane.
- In truth there are probably several.
- Gods by the bushel, gods by the pound... gods for every occasion, as it were.
- For they are Gods and such is the nature of proper noun Gods.
- Or claim to be, though that's a separate issue; what we call 'mortal' may not even be the same here as there.
- Though she cannot speak to the idea of divine foreknowledge because she really, really does not want it to be the case. Not when her very plan hinges on the gods not knowing what she's up to at all, let alone ahead of time.