For several months, Preston and Greg sent e-mails back and forth on big topics like God, religion, knowledge, evil, evolution, biology, destiny and the nature of reality. Preston believes in God; Greg sees insufficient evidence for God's existence. Over the course of their friendly debate, they tackle such cosmic questions as: Is religion rational or irrational? Does morality require belief in God? Do people only believe in God because they are genetically predisposed toward religion? How do you make sense of suffering in the world? Is this universe all there is? And what does it all matter?...