I recently ran across a post by an Arminian who believes that God's omniscience is a reason to reject Calvinism. He writes, "If the only way for God to know the future is to foreordain the choices and actions of his creatures, then God is not omniscient nor has the ability to be." There appears to be a hint of logic in that statement, but it falls apart under close examination.
As Creator of all things, God is, by definition, the Creator of everything that has been known, is known, and will be known. And as Creator, he is either sovereign over all creation or he isn't. I believe he is, and herein lies the nature of God's omniscience.
If something is foreknown to take place, then it must be foreordained. Otherwise there is the possibility that it might not happen. Put simply, God sees not just a particular future event, but everything leading up to that event. We can logically conclude that if the path is not already determined for a particular event to take place, then it cannot be foreseen, and there would exist the possibility that God could be wrong -- and that is an impossibility.
The only way around this dilemma is to admit that God does "foreordain the choices and actions of his creatures" in such a way that he is able to bring about all that he foresees. But that cannot be reconciled with Arminian free will.
If anything, God's omniscience is yet another reason to embrace Calvinism!