Open Theism is NOT based on this verse. The plain reading of this verse merely supports the doctrine.
Your reading your doctrine into the text here. I'd get into the details here but I'm not convinced that it wouldn't be wasted on you.
It isn't an excuse, its what the text of scripture will support.
On the contrary! Open theism is specifically about being able to read the text and take it to mean what it plainly states without having to turn whole passages into figures of speech that seem to mean the opposite of what they say.
John Sanders puts it most succinctly....
"The openness model is an attempt to provide a more biblically faithful, rationally coherent, and practically satisfying account of God and the divine-human relationship.." - John Sanders
You're lying to yourself here.
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Open theism is nothing less than a continuation of the same process begun by Martin Luther who dove head first into removing the influence of Rome from Christian doctrine. His injunction is echoed in the heats of open theists...
"Unless I am convinced by Scripture and plain reason, my conscience is captive to the Word of God." - Martin Luther
Only this time it isn't Roman dogmas that are being purged but rather it is the influence of pagan Greek philosophy that is through this time.
All world views have certain ideas that serve as its philosophical foundation. Almost always, one's worldview comes down to what one believes about God. This is as true of various Christian world views as it is of pagan or atheistic worldviews. In Christian circles, various doctrines dealing with God's attributes is referred to as "theology proper" and it is differences is their theology proper that is the bottom bedrock difference between Open Theism and Calvinism.
There are many varied characteristics of God that cover things like how big is God, how much does He know, how much power does He have, etc. Christians have words to refer to these quantitative attributes. Words like omnipresent, omniscient, omnipotent. The traditional understanding of these attributes of God is not founded in scripture but on the Classics (i.e. Aristotle and Plato). The omni-doctrines, as normally understood, as well as doctrines like immutability, impassibility, impeccability, et. al. were all likewise imported into Christian doctrine by Augustine of Hippo from the Classics and simply are not taught in the bible. (If you think otherwise, it is because you are reading those doctrines into whatever text you happen to be thinking of, which I'm happy to demonstrate, by the way.)
(Arminianism, while significantly different and less offensive to God's character than Calvinism, commits many of the same Aristotelian errors, just less consistently so. The two together, along with their variants comprise what is often referred to as the "Settled View". That term is fine but I've found that it is easier to simply refer to these doctrines as Calvinism or Augustinianism, which has become my normal practice.)
This, however, is not to say that God is not omniscient or omnipotent or omnipresent in some sense of those terms, God can do anything that He wants to do that is logically doable. He can be in all real places that He wants to be in when AND IF He wants to be there. Likewise, God knows and is able to keep perfect track of everything He wants to know and is able to find out that which He doesn't already know of that which is logically knowable. God cannot do the undoable (i.e. the rationally absurd) and as such cannot go to a place that doesn't exist or know that which cannot be known. This is the ONLY position that is consistent with the actual biblical material, which is a good thing because otherwise, the bible would falsify itself.
There are other attributes of God, attributes that deal with God's quality of character and personhood. God is living, personal, relational, righteous, just and loving,. These are the core attributes of the God we worship because they are the attributes that make Him worthy of worship. It is not how much God knows or God's size or how strong God is that makes Him holy, it is what He does with that knowledge and power that makes Him holy and worthy of praise. We do not worship God because He knows everything but because He is wise. We do not worship God because He is powerful but because He uses that power to practice justice and acts in the long term best interests of others at His own expense.
Now, here's the point of all this. It turns out that one is forced to choose which attributes to emphasize. One is forced, when forming one's doctrine, to choose which attribute(s) of God is paramount and which are not. The Calvinist picks one single attribute above all others. They, of course, are unwilling to admit this, but the fact is that they place supremacy on the doctrine of God's absolute immutability. The idea that God cannot change in any way WHATSOEVER is THE bedrock foundational precept upon which EVERY single distinctively Calvinist doctrine is built. That includes all of the TULIP doctrines and anything else that distinguishes Calvinism from all other forms of Christianity.
That, once again, is a point that I'm happy to demonstrate but to do so here would make this post, which is already too long, dramatically longer and so I'll wait for someone to challenge it. Suffice it to say that Open Theism is not the childish stupidity that taisto has ignorantly claimed. It is the result of a courageous allegiance to the righteous and loving character of our God and to, as Luther put it, "scripture and plain reason".