Greg Graffin is frontman, singer and songwriter for the punk band Bad Religion. He also happens to have a Ph.D. in zoology and wrote his dissertation on evolution, atheism and naturalism. Preston Jones is a history professor at a Christian college and a fan of Bad Religion's music. One day, on a whim, Preston sent Greg an appreciative e-mail. That was the start of an extraordinary correspondence. For several months, Preston and Greg sent...