One of the accusations that some people make about Open Theists is that since we think there have been instances where events have turned out differently than God wanted or expected, then God can make mistakes. This is simply not true.
When considering this issue, there are some key points to remember.
Number one, God can know all that is in existence. He can know all that is possible to know. I say "can" because God himself has gone on record saying there are facts he has chosen not to know, such as the details of what was occurring in Sodom.
Number two, the Bible tells us that God's manner of acquiring knowledge is through searching. See 1 Chronicles 28:9 and 2 Chronicles 32:31 as just two of many examples. The Bible does not tell us that every detail of everything that happens somehow automatically becomes a part of the knowledge of God. This is no way limits God, in fact, it shows how awesome his abilities are in that he can search out what is happening in the lives of all the people on earth and he can know the truth about them.
Number three, the only way it can be said that God made a mistake when he made a truth claim concerning a future event that happened differently than he expected, is if God has exhaustive definite foreknowledge or God himself had predetermined the event to happen just as he stated. But the Bible does not depict God as being a micro-manager in the affairs of mankind. Some people equate micro-management with sovereignty, but the Bible doesn't. In God's creation, he has granted free will to people so that they are able to comply with or resist his will. Certainly, if God decided to micro-manage every detail of the lives of all people, he could. But this was not his plan as the Bible clearly reveals. People are told they must choose who they will serve. Many resist his will. The danger of following him and turning back is real. God has given this freedom to mankind, and as a result, some people choose righteousness and some choose evil. Their choices are not forced upon them, though God may use the hardness of heart of some individuals to accomplish a specific task, and at times he has temporarily suspended a person's free will for this very reason (Pharaoh, Nebuchadnezzar). So what about the fact that God says some events did not occur as he expected or wanted? (See Jeremiah 19:5; Jeremiah 32:35; Isaiah 5:1-5 as examples.) Or that God stated something would happen but then it changed? We read this in 1 Samuel 2:30:
"Wherefore the LORD God of Israel saith, I said indeed that thy house, and the house of thy father, should walk before me forever: but now the LORD saith, Be it far from me; for them that honour me I will honour, and they that despise me shall be lightly esteemed."
Chris Fisher explains:
"The context of 1 Samuel 2:30 is about Eli’s worthless sons. They are evil, and God regrets giving His promises to Eli to have an eternal priesthood. Verse 30 is God revoking His eternal promise. Although God had promised Eli a house “forever”, He needs to recall that promise and replace it with a conditional promise. God had promised, “but now” God promises something else. The change of promises is explicit. The first promise is “far be it from” God. God is distancing Himself from His original promise in the most explicit of terms.
The fact that the new promise is a conditional promise suggests that the original promise was not conditional. If the original promise was conditional, then there would be no need to replace it with a conditional promise. The original promise could have just been fulfilled without change.
1 Samuel 30 is a clear incident of God experiencing a change that He did not expect. The text is clear and unambiguous. This unexpected change forces God to revoke an eternal promise, and replace that promise with something that can adapt to situations as they change. God is acknowledging that He does not know the future (exhaustively - GC) and will be able to adapt to a future He does not foresee." (Parenthetical insertion is mine)
It is simple - when someone else is to blame, it is not a mistake on the part of God.
Christian parents are rightly concerned with who their children marry. A mother and father can pray for a Godly husband for their daughter, and though God does not force certain people to marry, he can influence the situation. God can bring a man that is following him into the daughter's life. They marry and have children and all is well for several years. But then, due to various factors, the man begins to drift away from God. He hardens his heart toward God's correction and his life becomes characterized by drunkenness, violence, and infidelity. Did God fail the parents and the daughter? Did he make a mistake? Based on the theology of many professing Christians, either God knew this was going to happen, or it was God's will for it to happen and he decreed it to happen. Under either of these two explanations, it can certainly be argued that God failed them, though the first group would say God knew it but prepared for it (which leads us to ask, why didn't God prepare for it by not bringing them together to begin with?) and the second group would say that God caused this evil for a greater good (which is nonsensical to anyone except a Calvinist).
Who made the mistake in this situation? It certainly was not God. It was the husband who strayed from God and turned his heart toward evil. God made a decision to bring these two together in marriage based on what was true at the time. Both were his followers. But one turned from God and ruined what could have been a good marriage. When God searched the man's heart, he fit the bill when it came to what the parents and the daughter were praying for. His fall into evil was not God's doing, it was his own.
When God says or expects, based on current knowledge, that such-and-such will come to pass, but free agents change course and cause something else to occur, that is not a mistake on God's part. God is not as concerned with the idea of him having to exhaustively know all future occurrences as some people are. God's ultimate plans are never thwarted, though individuals may resist his will and cause things to turn out differently than God expected or wanted. God can do as he chooses, though it is important to remember that a part of what he chooses is allowing free agents to have "say-so" in world affairs. Rather than trying to force biblical texts to mean something other than what they clearly say by calling them anthropomorphisms, we should bow to the sovereign God who does not need to control or even know the future exhaustively in order to accomplish his purposes. He is infinitely resourceful and worthy of our obedience and praise.