In the Bible, some of the people ask Jesus for a sign. They ask that he prove his identity and authority, probably they have something bright and flashy in mind: lightning from heaven, spheres of fire, something like this. Christ does not give them the supernatural sign they desire. At least, he doesn’t in a way that they see and understand. Is it not enough that he has healed the sick? That he has cast out demons? One finds an attitude like this from many atheists today: “I’ll believe in God when he shows me he’s real.” How does one respond to this?
One class of atheists simply will not believe in God. They could be taken up to heaven and they wouldn’t accept the truth of heaven: like the dwarves in C.S. Lewis’ The Last Battle. They’re so hardened, so determined to continue in disbelief, that they believe they are still in the dingy stable, despite actually being on a green lawn on the borders of Aslan’s country. Quite frankly, there is no response to this type of atheist who asks for a sign. They might even get one, but it wont be good enough, they will always find some way of explaining it away.
There is another class of atheists who reason has led to believe that God is not a plausible explanation. Reason has led them to the conclusion there is no God. This class there is a bit more hope for. A sign may indeed bring them to faith. But as with the Jews in the time of Christ, this sign may not be quite what is expected. Jesus performed miracles, and pardoned sin, anyone who was willing to give him a chance could come to the conclusion that he was in fact giving them signs: he was, is, and always will be broadcasting loud and clear for those willing to consider objectively for a moment.
There is still another class, those who would rather believe in anything but the God of the Christianity. These may seem similar to those of class one, but there is a stark difference. Atheist is perhaps not even a good term for these non-Christians. They may claim to be atheist in order to do away with God, but atheist is in fact an incorrect term for them. This type will cling to whatever alternative they have no matter what, they may say they are atheist and yet have their own “god”. Atheism in this case is very much a religion. The atheist of this type is the one that will attack Christianity at every level possible, with all might and main. They will do anything to destroy, disprove, and slander this God who is so offending to them. A sign here is useless.
Three classes of atheists, or more appropriately, non-Christians have been presented. Class one and three will not be converted by a sign, nor by reason. Class two there is a chance with. What, one may ask, is the hope for those of class one and three? How can one convert them if reason and miracle are useless? There is only one other alternative: reason has failed, and a blunt, outright miracle or sign has failed, but prayer can still be employed. Properly speaking, humans never convert other human beings at all. God is the one who does the converting, but he may choose to do it through a human, or the prayers of a human.