Thank you to Got Questions (gotquestions.org) for the following article.
The only quibble I have is that they reference the ESV version of the Bible. I prefer the King James as I am persuaded that it is the most faithful translation we have today. For more on this see https://www.chick.com/information/why-the-kjv
Question: “What is open theism?”
Answer: “Open theism,” also known as “openness theology,” the “openness of God,” and “free will theism,” is an attempt to explain the foreknowledge of God in relationship to the free will of man. The argument of open theism is essentially this: human beings are truly free; if God absolutely knew the future, human beings could not truly be free. Therefore, God does not know absolutely everything about the future. Open theism holds that the future is not knowable. Therefore, God knows everything that can be known, but He does not know the future.
Open theism bases these beliefs on Scripture passages which describe God “changing His mind” or “being surprised” or “seeming to gain knowledge” (Genesis 6:6; 22:12; Exodus 32:14; Jonah 3:10). In light of the many other Scriptures that declare God’s knowledge of the future, these Scriptures should be understood as God describing Himself in ways that we can understand. God knows what our actions and decisions will be, but He “changes His mind” in regard to His actions based on our actions. God’s disappointment at the wickedness of humanity does not mean He was not aware it would occur.
In contradiction to open theism, Psalm 139:4, 16 state, “Before a word is on my tongue you know it completely, O LORD…All the days ordained for me were written in your book before one of them came to be.” How could God predict intricate details in the Old Testament about Jesus Christ if He does not know the future? How could God in any manner guarantee our eternal salvation if He does not know what the future holds?
Ultimately, open theism fails in that it attempts to explain the unexplainable—the relationship between God’s foreknowledge and mankind’s free will. Just as extreme forms of Calvinism fail in that they make human beings nothing more than pre-programmed robots, so open theism fails in that it rejects God’s true omniscience and sovereignty. God must be understood through faith, for “without faith it is impossible to please God” (Hebrews 11:6a). Open theism is, therefore, not scriptural. It is simply another way for finite man to try to understand an infinite God. Open theism should be rejected by followers of Christ. While open theism is an explanation for the relationship between God’s foreknowledge and human free will, it is not the biblical explanation.
Recommended Resource: No Other God: A Response to Open Theism by John Frame