Open theism is the belief that God does not have exhaustive knowledge of future events. He knows everything that can be known, but since the future does not yet exist, by definition, he cannot know the future. While he does not know the future, because he has perfect knowledge of the present, he can often accurately predict what will happen in the future. In open theism, God sometimes predicts the future incorrectly. Another related belief is process theology which goes beyond open theism by saying that God is not immutable or unchangeable. God changes with the world and is dependent on it. While open theism and process theology are distinct from each other, open theism is essentially a form of process theology because God is constantly gaining new information and adapting in time to these changes. God is learning from us as he observes creation and is able to make more accurate predictions of the future as his knowledge of human behavior grows.
One of the most glaring problems with open theism is that it makes penal substitutionary atonement impossible since God did not know we would exist when Christ died on the cross. This means that our sins which God did not know about could never have been imputed to Christ when he suffered on the cross. In contrast to open theism, Scripture teaches that our personal sins were laid on Christ (Isa 53:5-6; Heb 9:28; 1 Pet 2:24).
Open theism also makes predictive prophecy impossible since God does not know for certain what the future holds. The entire book of Daniel is a testament to God’s exhaustive knowledge of future events. Daniel 11 is especially revealing since it chronicles the entire history of the Seleucid and Ptolemy dynasties hundreds of years before they take place. An additional piece of evidence that Daniel was written before the time of Alexander the Great is recorded by Josephus in Antiquities 11.8.5 telling how Alexander was shown the book of Daniel by the Jews which they believed spoke about him.
If God does not know the future, then he is in the same category as the false gods of Isaiah 41:21-26 who cannot prove they are true deities because they do not know the future:
“Set forth your case, says the LORD; bring your proofs, says the King of Jacob. Let them bring them, and tell us what is to happen. Tell us the former things, what they are, that we may consider them, that we may know their outcome; or declare to us the things to come. Tell us what is to come hereafter, that we may know that you are gods; do good, or do harm, that we may be dismayed and terrified. Behold, you are nothing, and your work is less than nothing; an abomination is he who chooses you. I stirred up one from the north, and he has come, from the rising of the sun, and he shall call upon my name; he shall trample on rulers as on mortar, as the potter treads clay. Who declared it from the beginning, that we might know, and beforehand, that we might say, ‘He is right’? There was none who declared it, none who proclaimed, none who heard your words.”
God tests the false gods by demanding that they do something only he can: predict the future. But the Lord proves that he is the true God, not only because he foretells the return of Israel from exile, but he gives the name of the Persian king who will do it before he was even born (Isa 44:28; 45:1).
How could Jesus say to Peter in Matthew 26:34, “Truly, I tell you, this very night, before the rooster crows, you will deny me three times” if he did not know the future? If Jesus, according to open theism, had simply made an educated guess, then he took the risk of becoming a false prophet since Deuteronomy 18:20-22 says that any prophet who predicts the future wrongly is to be put to death. But Jesus could not possibly have predicted the future wrongly because he is God and God knows all things (John 16:30; 1 John 3:20). The Bible declares that God’s knowledge is perfect (Job 36:4; 37:16). How could God’s knowledge be perfect if he is constantly gaining new information? God exists above all categories of time and does not experience time as a creature does (2 Pet 3:8).