When reason has reached its limit, there are two possibilities. We can stop, or we can continue onward. Some thinkers, such as philosopher Ludwig Wittgenstein, argued that beyond what we can assert by reason we should assert nothing. “We don’t get to the bottom of things,” Wittgenstein wrote, “but reach a point where we can go no further, where we cannot ask further questions.” To the query, “What lies beyond death?” Wittgenstein refused to answer one way or the other. He certainly didn’t, with the misplaced confidence of Richard Dawkins or Sam Harris, answer, “There is nothing.” He couldn’t say that because he didn’t know

This response—”I don’t know”—is an expression of a kind of agnosticism. It involves a suspension of judgment in the face of igno rance that is clearly superior to atheism. Yet curiously this form of agnosticism is shared by the religious believer. The religious believer also does not know. The Bible says in Hebrews 11:1 that faith is “the substance of things hoped for, the evidence of things not seen:’ If the believer knew, there would be no question of faith. Consider this: I don’t have faith that my daughter is in the seventh grade. I know my daughter is in the seventh grade. I -haven’t been to heaven, and so I cannot say that I know there is such a place. But I believe that there is. Faith is a statement of trust in what we do not know for sure. Faith says that even though I don’t know something with certainty, I believe it to be true.

From this we draw a conclusion that will surprise many atheists and even a few Christians: doubt is the proper habit of mind for the religious believer. There is a story in the Gospel of Mark 9:17-24 about a man who came to Christ to cure his son of possession by an evil spirit. Jesus said to him, “If you can believe, all things are possible.” And the man replied, “Lord, I believe. Help thou mine unbelief.” This is every true believer’s prayer. The Christian has faith even though he is not sure, while the unbeliever refuses to believe because he is not sure. But they agree in being unsure. The skeptical habit of mind is as natural to Christianity as it is to unbelief.