Open Theism: A Philosophical Objection

Open Theism was a hot topic in the church a few years ago, and I know its a little strange to revisit the issue at this late date...But, having briefly discussed the issue the other night with a couple of young Pastor friends, I thought I would write down my continuing objection to the position. Many of you (not that there are actually many of you readers) may not be aware of the debate. You'll have to look elsewhere for fuller treatments than can be offered here. In short, it is the rejection of the traditional view of God's foreknowledge as absolute, or exhaustive. Open theists believe that the future does not have the ontological status of existence (since it hasn't happened yet) and therefore does not present itself as available to be known. They believe in omniscience, but assert that divine omniscience comprehends only those things that are capable of being known, i.e., that exist as potential objects of knowledge.

Here is a short version of my continuing objection to "Open Theism".

Open theists believe that though God almost never overrules the exercise of free will He can and does (or has done) do so in a narrow field of instances, namely in those instances that carry the possibility of substantively disrupting the flow of redemptive history. There are certain outcomes that must be achieved (e.g., the cross) in order to insure that history arrives at its intended goal. The necessary choices to effect these outcomes are thought of as momentous.

My question is this. If there exists within the Divine cognition a mechanism that distinguishes between momentous and non-momentous choices, exactly how does it work? It seems to me that it can only work by extrapolating the consequences of every human choice into the future ad infinitum. And, if God has the capacity to extrapolate the consequences of every human choice into the indefinite future, then how does this differ from what has traditionally been called exhaustive foreknowledge?