In Open Theism, God does not exhaustively know the future. He also makes mistakes, learns, and has regrets because of His ignorance of future events. Open theists say that God does not know future free will choices of people because He either chooses to not know the future or because the future is unknowable. If this is so, then I cannot help but ask whether or not the God of open theism can be trusted. After all, God doesn't know the future, can make mistakes, and actually changes His mind.
Let's say that you have a very important and biblical need that you want to pray about. Let's further say that you have just learned that God can make mistakes, that He must adapt to human choices, and that He does not know the future exhaustively. Would you feel confident in approaching God if you believed He could goof, that He would have to go through a learning curve, and that He did not know the future choices of people? In my opinion, it would not elicit confidence.
The prayer of an Open Theist
Now, I admit right away that I am exaggerating the forthcoming prayer a bit, but it is to make a point; namely, that open theism undermines trust in God. Let's see how a prayer might go to a god who is fallible, who makes mistakes, and who does not know the future exhaustively. For this purpose, I will have a father named Fred, who is a recent convert to open theism, offer a prayer about his daughter.
"O Lord, I come to you now with a request for help. My daughter has become mixed up in drugs and fornication with her boyfriend who is not a Christian. I have witnessed to them both, but they are both not interested. I am so concerned about my daughter and I ask you Lord to deliver her from her sinfulness and cause her heart to repent.
O Lord, I know that you gave us free will and that you will not interfere with our choices and that you don't really know for sure what will happen, but Lord, can you please work in her heart to change her and bring her to repentance?
...there is a pause in his prayer....
O Lord, I am confused on what to ask. I want my daughter to change her ways, and I come to you for help. But, how can that be if you cannot change her heart since it is up to her to change? How then can she repent if she doesn't want to? Perhaps Lord, perhaps you could cause someone to enter their lives who would convince them of the error of her ways. Maybe you could send someone...but, Lord, how would you do this if you don't know whether or not anyone would choose, of their own free will, to help her. You can't make them do it. Lord, do you even know if she will repent? Oh wait, that's right, you don't.
Lord, I sincerely hope that you don't make a mistake with her and take any risks with her.
Lord are you able to make a difference in her life?"
How could anyone trust a god who makes mistakes, who learns, who can't control the hearts of His people, who must wait to see what happens? Is this the stuff of confidence?