There is another irritating problem with the idea of omniscience: it contradicts the attribute of omnipotence. If God knows the future with infallible certainty, he cannot change it— in which case he cannot be omnipotent. If God can change the future, however, he cannot have infallible knowledge of it prior to its actual happening— in which case he cannot be omniscient. (This is similar to the issue of in what sense, if any, God can be said to have free will. Does God know his own future decisions? If so, how can those decisions be free? Perhaps God does not make decisions. If so, how can the idea of volition apply to a being with no decisions— and hence no choices— to make?)

Smith, George H.. Atheism: The Case Against God (The Skeptic’s Bookshelf) (pp. 74-75). Prometheus Books. Kindle Edition.

Theologians have devised a number of unsuccessful ways to reconcile omniscience and free will. One method is to argue that God’s foreknowledge does not “impose” itself on the course of events, and God knows a free action “according to the nature of the event itself— which is free.” This, of course, solves nothing, because it evades the central issue. How can an event be “free” in the first place, if God has infallible knowledge of it prior to its happening? Another approach has been to argue that “God does not exist in time at all” —but this serves only to strengthen agnosticism. Other attempts at reconciliation are similarly unimpressive, so it seems that the Christian is forever plagued with the dilemma of preaching a religion of salvation to a world of men who, according to the doctrine of omniscience, are nothing more than automatons.

Smith, George H.. Atheism: The Case Against God (The Skeptic’s Bookshelf) (p. 74). Prometheus Books. Kindle Edition.

From How People Misunderstand Open Theism

I’m always puzzled as to why many defenders of the classical theism spin the debate with open theists as a disagreement over the perfection of God’s knowledge. For example, they publish books with titles like How Much Does God Know? (Steven Roy) and What Does God Know and When Does He Know It? (Millard Erickson). Since open theists believe God always knows everything, why do they continue to argue as if we don’t?

Part of the explanation, of course, may be simple propaganda. My sense is that, while spinning the debate as about God’s knowledge rather than the nature of reality certainly is advantageous for the purpose of propaganda, the critics who argue this way also seem to sincerely believe what they’re saying. How can this be?

While researching some ancient philosophers who influenced theologians like Augustine and Boethius, I uncovered something that may help explain this curious phenomenon. Let me briefly explain.

First, Plato argued that we see not by light entering our eyes (as we now know is the case) but by light proceeding out of our eyes (Timaeus 45b). For Plato, seeing is an active, not a passive, process. Since knowledge was considered to be a kind of seeing, Plato also construed knowing as acting on something rather than being acted upon (Sophist 248-49). I’ve discovered that this mistaken view of seeing and knowing is picked up and defended by a host of Hellenistic philosophers.

Second, several Neoplatonistic philosophers (Iamblichus, Proclus and Ammonius) used this theory of eyesight and knowing to explain how the gods can foreknow future free actions. They argued that the nature of divine knowledge is determined not by what is known but by the nature of the knower. Since they assumed the gods were absolutely unchanging, they concluded that the gods knew things in an absolutely unchanging manner, despite the fact that the reality the gods know is in fact perpetually changing. This allowed them to affirm that the future partly consisted of indefinite (aoristos) truths (viz. open possibilities) while nevertheless insisting that the gods knew the future in an exhaustively definite, unchanging way.