John Piper on The Sovereignty of God and Prayer

Common questions asked of Reformed believers is why pray if everything is predestined by God? Why evangelize if God has already determined who He will save? Piper reverses the question and asks:

Now I would like to turn the question back to my questioner: If you insist that this man must have the power of ultimate self-determination, what is the point of praying for him? What do you want God to do for Him? You can't ask that God overcome the man's rebellion, for rebellion is precisely what the man is now choosing, so that would mean God overcame his choice and took away his power of self-determination. But how can God save this man unless he act so as to change the man's heart from hard hostility to tender trust?

The full article is here: The Sovereignty of God and Prayer