Open Theism is the logical conclusion of consistent Arminianism, but takes their logic one step further than Classic Arminians would. It affirms that since man has a libertarian free will, God cannot know the future. If God knew the future, he would also know the certainty of our future choices, that could not be otherwise. Given this premise, the open theist argues that we cannot chose differently than what God foresaw so we couldn't have free will. Therefore God makes highly educated guesses as events transpire. In the end, God is controlled by His creation (time).
The Open theist affirms that God cannot exhaustively know future events for if God had known from all eternity everything someone will do in the future, then the fact that they will choose the thing has been settled in God's mind, and cannot be otherwise. Hence, the person has no more power to alter the fixed-past-settled-with-certainty fact of what they shall choose to do than they have to altar any past fact. Therefore, they reason, that they cannot make free (or morally responsible) choices that God knows with certainty they will make. The Open theist views the possibility to choose otherwise as the sin qua non of moral responsibility. therefore God must only know my future choice as a possibility, not a settled reality.
Greg Boyd, one of the main proponents of OT, claims that he unequivocally affirms that God possesses every divine perfection, including the attribute of omniscience, that God perfectly knows everything THERE IS to know. Open Theists affirm that the future is open to various possibilities and that this is outside the scope of knowledge since it has not happened yet. What may or may not happen in the future, according to Boyd, has no truth value. Of course this would mean that God would be confined within time itself (something He created).
thus, the proponents of Open Theism erroneously deduce that time (God's creation) exerts a superior power over His ability to know anything outside the present, by confining Him to the present ... within the finite creation. By this view, the proponents of Open Theism deny the unlimited power of God to know the beginning from the end and, by default, declare that there is something greater than God himself (time).
Remember the former things of old: for I am God, and there is none else; I am God, and there is none like me, Declaring the end from the beginning, and from ancient times the things that are not yet done, saying, My counsel shall stand, and I will do all my pleasure: Calling a ravenous bird from the east, the man that executeth my counsel from a far country: yea, I have spoken it, I will also bring it to pass; I have purposed it, I will also do it. - Isaiah 46:9