If there is an omniscient God, then he knows you better than you know your best friend. Better than anybody has ever known their best friend. He knows every little nook and cranny of your psychology, how your mind works down to the last detail. He's monitored your every action throughout your whole life, and done a thorough analysis of your behaviorisms and decision-making skills. He knows exactly how to put himself in your shoes. How could he not know what you're going to be up to in the future?

Of course, there is no God, and I still believe there's no such thing as free will. The way I explain it is like this. Everything either has a cause, or is completely random. That's basic logic. Every event that ever happens is the result of a chain of causes, except for quantum things which are completely random and can't be predicted. If something is not random, it must have a cause, and if something has no cause then it must be random. Our thoughts are no exception to this logical tautology.

A lot of people think we make decisions in our heads that don't have causes in the real world. That is, it's not just a chemical reaction in your head; it's not something that's just inevitable given your perception of reality and the structure of your brain. However, they fail to realize that it cannot be this way unless your thoughts are random. If one decision was not chosen over another for some definable reason, then it was chosen at random.

The brain is nothing more than a complex computation device that tries to calculate what the best decisions are based on the information that's already in the brain and the new information that is streaming into the brain all the time. Your thoughts have definable causes: your experiences with the real world, your memories, your genetically programmed instincts, whatever chemicals might be affecting your brain at the time, etc. If there were no causes which resulted in your stream of thought, it would be completely random, and you'd go psychotic.

Human thoughts are no exception to the chain of causes and effects (plus quantum randomness) that has been going on since the Big Bang. As far as I'm concerned, "free will" is an incoherent concept. How can something not be random and not have definable causes that makes it predictable ahead of time? It's not logically possible.