“Imagine that you're an intelligent extraterrestrial, concerned only with verifiable truths. You discover a species that has divided itself into thousands - no, by now millions - of tribal groups holding an incredible variety of beliefs about the origin of the universe and the way to behave in it. Although many of them have ideas in common, even when there's 99% overlap, the remaining one percent's enough to set them killing and torturing each other, over trivial points of doctrine, utterly meaningless to outsiders. "How to account for such irrational behavior? (...) religion was the by-product of fear - a reaction to a mysterious and often hostile universe. For much of human prehistory, it may have been a necessary evil - but why was it so much more evil than necessary - and why did it survive when it was no longer necessary?”