Proof of God would undermine free will
One apologetic argument for the lack of clear evidence for God is that such proof would undermine humans' free will: such evidence would leave us no choice but to believe in God, and his glory and magnificence is such that we would have no choice but to worship him. Thus, God chooses to remain hidden in order that we should come to believe in and worship him freely.
This is not a deductive argument, of the form "this is what we know about God, therefore we should expect to see such-and-such effects." Rather, it is an ad hoc excuse for the lack of solid evidence for the existence of God. A person making this argument presupposes that God exists but concedes that there is no good evidence for his existence; this argument is one way to reconcile the two.
Differences among theists
This argument is also at odds with the behavior of many theists, who seek out evidence for God. If an omnipotent, omniscient god truly wanted to remain hidden, then there should be no miracles, no relics (such as the Shroud of Turin), no miraculous apparitions; intercessory prayer should not work. Yet such evidence is sought by many.
Counterarguments within Christianity
In the Bible, many people were given sufficient evidence for God's existence, including Abraham, Moses (who spoke personally with God), Jesus' apostles and followers, who witnessed miracles first-hand. Therefore either:
- The argument that God cannot reveal himself without removing free will is flawed.
- God took away some people's free will, but not others'.
- The Bible is in error.
According to Christian tradition, Satan was originally an angel who rebelled against God. It is reasonable to assume that Satan knew that God exists, since they were coworkers. And yet Satan rebelled, and chose not to worship God. Thus, knowledge of God's existence does not compel worship. Furthermore, if the god of the bible really did exist, and provided proof of his existance, there would still be people who would hate and not worship him due to his actions in the old testament.
Similarly, Judas Iscariot had ample evidence of Jesus' divinity, and still betrayed him.