Christian beliefs about God are many. Along with the traditional beliefs of personality and perfection, we have the three 'Alls'. All-loving, all-knowing and all-powerful. And in addition to this, most Christians believe that people have free will, which is intrinsic to certain justifications of evil.
Arguments that have attempted to derive a contradiction from free will and omniscience have existed for a long time, from Aristotle to Maimonides. These people have felt that omniscience posed a problem for free will, if not rendered free will impossible.
The argument against free will basically goes like this. If God knows about the future, then it entails that he knows my future choices. If God knows what I will do tomorrow, then it is logically impossible for me not to do it.
Now it is important for us Christians to defend free will. Free will is the greatest gift that a God could ever bestow on a creature. Free will also lies at the heart of the best defense against the existence of moral evil in our world - the free will defense. If free will does not exist due to divine foreknowledge, then God is in a way, responsible for our moral evil.
That nature of the argument is that it alleges if God knows something, then it must happen. Surely God cannot be wrong. Specifically if God knows I will do an act, then it is a fact that that act will occur. If that act did not occur, it would not be a fact.
It is here that we see that with the formulation of the argument, wider conclusions are drawn. Specifically that it is not the existence of God's foreknowledge that is the problem, but the existence of any definitive statement on our future choices. And such future statements are thought to exist, in the form of facts.
Consider the statement, 'Martin Luther King was born in 1929'. That is a fact, we know that now. The question is, if it is a fact now in 2005, and if it is a fact, how can it not be true in 1920? Or 1900? Or 1 AD? Or from the beginning of the universe? Surely all facts must be true at all times?
Therefore I think it is valid to draw the conclusion that if this argument is correct, not only does it render free will impossible, and thus disproves the Christian God, but renders all free will impossible, due to the nature of facts (unless every world is actualized or something like that.)
This is the argument in question, related in one of it's many variations
There are 2 major objections to this argument. Also, remember one can relate the same argument with 'it is a fact' inserted instead of God and derive the same conclusion.
First objection, and the one that is maintained by such distinguished theologians as William Lane Craig, hold that because I will do something, it doesn't mean that I must do something. Consider:
1. God knows I will choose A over B in 2007
But from (1) it does not entail that 2. I must choose A over B in 2007
1. It is a fact I will choose A over B in 2007.
But (1) does not entail 2. I must choose A over B in 2007.
If (2) does not entail from (1) then the anti-free will argument collapses.
Another objection to the argument is that even though it is a fact that I will choose something, even though this is true beforehand does not mean that I had no choice. Consider:
1. It was true from the beginning of the universe I would choose A over B in 2007.
But (1) does not mean that 2. It was determined from the beginning of the universe I would choose A over B in 2007.
The fact alleges the choice. The choice itself took place in 2007, not the beginning of the universe.
Consider which is more reasonable
1. God's foreknowledge, that Jeff will choose A over B in 2007, is contingent on Jack's choosing A over B in 2007.
2. Jack's choice of A over B in 2007 is contingent on God's foreknowledge.
1. The fact that Jeff will choose A over B in 2007, is contingent on Jack's choosing A over B in 2007.
2. Jack's choice of A over B in 2007 is contingent on the fact he will do so.
This has interesting repercussions for the notion of God. If we think of God as a 'fact-holder', which is that God has access to all facts about everything. This would mean that God doesn't receive foreknowledge from predictive capabilities, but rather from having super-access to all facts.
Now we come to the interesting question, how does God know the future?
Well, you have the option that God is essentially a fact-holder, above, but there are other ideas.
One idea is that God is timeless. If God is timeless, then it means that every moment in our time will essentially be the same moment to him. All our moments will exist with His timeless moment simultaneously. This would mean that, assuming God has great powers of observation, God could know about our choices by directly observing them happen.
Of course, some Christians don't actually believe God has foreknowledge of our choices at all. This is especially true of liberal theologians/philosophers. Instead of knowing future choices, omniscience is re-defined to mean only knowing that which it is possible to know, and these Christians don't believe it is possible for anyone to know what a future free willed choice will be, it would be like knowing a 4-sided triangle.
Finally I would like to ruminate on where the objection comes from. Let me make a proposal that one possible reason comes from the nature of our predictive knowledge. Necessarily, for us to know anything for certain, then we must narrow it down to one possibility. If God knew our free choices by prediction, barring some kind of transcendent power, God would have to nail our choices down to one (the choice we must do).
Another idea is that we know intuitively that 'God' cannot be wrong. Neither can a fact be wrong. So if we were in danger of proving God wrong by choosing differently, there must be some kind of 'force' that makes sure we don't, and due to the infinite damage proving God wrong would cause, this force must be infinitely great.
Of course, such an idea would pose an absurd limitation on God's foreknowledge, which is to say it is in the manner of our knowledge.
To conclude the analysis of the objection, even if we accept the argument, as applied to God, then there exists 2 possible Christian views where God is still omniscient. The first is that God is a historical observer, and the second is that God does not in fact, know future facts about our choices at all.
But I doubt that this is necessary due to 2 major flaws in the argument, which is that 'will' doesn't equal 'must' and that God's knowledge is contingent on our choices, not the other way round. In other words, if I would have choose differently, God would have know differently.