Here is the problem as I see it. For an omnipotent God to exist, He by definition must be able to see the future. This means that even before my conception, he knows what choices I will make, and to that effect he knows whether I will follow him or not. Yet if this is true, then that means that I really have no say in the matter. This demands me to be a fatalist, and to deny the existence of a free will.
Yet if I claim that there is free will, then that is to say that I have a choice in whether I follow "Gods plan" or not, and in so doing I can go against him if I choose. However, if I am able to refuse god, then I can interrupt his plan. And if I am able to interrupt his plan then God is not perfect. And a perfect God is not God.
Here is the problem from another angle. If God is not omnipotent, which is to say that if he cannot see exactly what is going to happen at all times, then he can make a mistake. There are things that he does not know, and so there is a chance that he can make a wrong decision. But again, a fallible God is not God.
I'll give an example. Let's say that it is in God's plan that I find the cure for AIDS. He has created me for the purpose of enlightening the world to the one way to rid themselves of the AIDS virus. That is what he has in store for me.
If I have free will, then I can choose at any time to be a sailor, or better yet, to kill myself. I can throw myself into the path of a bus. And if I do that tomorrow, I will have never discovered the cure for AIDS. I have interrupted God's plan, and thus proved that he can make a mistake. He designed something for me but I use my free will to change the course of his plan. That is not to say that he cannot impart the same gift on someone else. He, as God, can create another person and make the cure for AIDS his destiny. But it was meant for me, and thus I have proven him fallible, and disproved his existence.
But maybe it was in God's plan for me to only do a part of the work, and it was really someone else's destiny to put it all together; To truly discover the cure for AIDS. In this case, then I have not really disrupted Gods plan at all. But I have fulfilled my destiny, whether I liked it or not, and thus I have no free will.
This idea is supported even in the bible itself. One of the most well known stories, Peter's denial of Jesus (John 18, 12-27) supports this perfectly. Jesus tells Peter, "The cock shall not crow till thou hast denied me thrice" (John 13, 38) which constitutes a definite prophecy. The motives of Jesus' telling Peter this can be debated all day. Was Jesus' prophecy an act to elect faith in Peter even after Jesus' condemnation? Was his vocalization of the future an attempt to create a Cassandra paradox and avoid Peter's denial of Him? What Jesus' intentions in this were I do not mean to debate in this paper. What is critical in Jesus' actions are three fold, the first of which is the lack of the Cassandra paradox even with the knowledge of the future that Peter had. The Cassandra paradox is the idea that by knowing the future one will change it. For example, if I make the true prophecy that you will be killed when you go home after...