In the time of Jesus, Greek religion had already mainly converted to Platonism. As such, Homer became an embarrassment. In order to salvage Homer, Greek theologians began reinterpreting him. Here is Plutarch in Morals:
So, when thou readest in Homer of Gods thrown out of heaven headlong one by another, or Gods wounded by men and quarrelling and brawling with each other, thou mayest readily, if thou wilt, say to him, —
Sure thy invention here was sorely out,
Or thou hadst said far better things, no doubt; [Il. VIII. 358.]yea, and thou dost so elsewhere, and according as thou thinkest, to wit, in these passages of thine: —
The Gods, removed from all that men doth grieve,
A quiet and contented life do live.
Herein the immortal Gods for ever blest
Feel endless joys and undisturbed rest.
The Gods, who have themselves no cause to grieve,
For wretched man a web of sorrow weave. [Il. VI. 138; Odyss. VI. 46; Il. XXIV. 526.]For these argue sound and true opinions of the Gods; but those other were only feigned to raise passions in men.
What is happening here is that Homer describes the gods as quarrelsome. The Greeks did not want to believe it. As such, they adopted the same technique the Calvinists now do when speaking about God in the Old Testament. Moses just wrote Genesis 18 or Exodus 32 for our sake. Moses did not really mean what he wrote. Moses only did so to raise our own emotions.
The reader can judge how intellectually honest the Greeks were treating the texts of Homer, and as a parallel, judge how intellectually honest the Calvinists treat the text of the Old Testament.
reality is not optional 
In Genesis 22, the scripture states that God tested Abraham. This statement is repeated in the letter to the Hebrews. The outcome of the test is that God declares ‘Now I know that you fear God’. One of my Calvinistic interlocutors insisted that ‘God was not learning anything here’ and that the purpose of the event was that Abraham could learn. It is amazing what presuppositions can do to our reading of scripture.
In my experience, though, merely debating on the meaning of various verses and their contexts is endless. So I also try to point out the presuppositions that are governing the interpretations in the hope I can make progress towards sound and open belief.
The problem that Calvinists have with open theists is simply that it seems to them that the open theist God does not know anything at all. He did not know what Abraham would do before he did it. He must always be waiting to see. He must always be reacting.
Some open theists say that God chooses not to know, others that he simply does not know. Neither of these notions seems satisfactory to me either. We need to look at our presuppositions too!
The Calvinist is assuming a) that the entity Abraham is an entity that is capable of being completely defined, b) that it is possible to predict from this definition what Abraham would do in any given context and c) that God is fully aware of the definition of Abraham and hence is able to make perfect predictions as to his actions.
Often, the open theist’s answer is merely to dispute c) but really, presuppositions a) and b) are far more significant. If a) and b) were true, then I would expect c) to be true anyway and if a) and b) were true and c) was false, then I would probably revert to a reformed theology. It somehow doesn’t seem to be worth arguing much over. The battle (and it is a battle in most cases) has been turned into an arena where the Calvinists feel a lot stronger.
My method is to admit that yes God does know everything under point c) (at least for the time being as it will require some clarification) but to turn back the discussion to the real issues of a) and b) for it is these that are at the heart of openness.
The point is that God’s knowledge of Abraham is one of relationship, not of objectivity. God knows Abraham as he experiences him. This is dynamic knowledge, not static knowledge. Because Abraham is an open being he is a priori undefinable. He is what he is in relationship to God, to others and to the world. We can say things about him after the event but not before the event. For example if Abraham stops eating figs, we can say as a matter of definition that Abraham doesn’t eat figs. Or if Abraham starts arguing a lot with everyone, we can then say that Abraham is argumentative. We don’t just look at him and say that he is argumentative. We can’t know that just by looking at him. Even if we could see into his mind, it would not tell us what we want to know. The only way we can know if he is argumentative is if he argues with people. We don’t say it and then wait to see if it will happen. Our knowledge of Abraham is mediated by our experiences of him and the statement ‘Abraham is argumentative’ is not an absolute truth but rather one that is formed as a summary of those experiences. Hence we say that knowledge is relational.
The point about the test of Abraham is that God wants to go through that particular experience with him. God is still in charge, he still knows everything he needs to know about the situation. He is in a positive relationship with Abraham and wants to develop that relationship. Nothing is ungodly or less than godly about this situation. Indeed, the idea that God’s knowledge of his people is the relationship he has with them, seems far more godly to me than if God makes a prediction of our every action based on an absolute and static view of us as individuals.
Thanks for the comment. One thing I would add is that the text might tell us something (like God didn’t know for certain what Abraham would do) and it is fine for us to work backwards, checking our suppositions until we find one that needs to be modified to accomidate the found fact.