We have been witnessing in recent years a vigorous and almost concerted resurgence of atheism. The writers Richard Dawkins, Christopher Hitchens, Sam Harris and Daniel Dennett—the "Four Horsemen of the New Atheism," as they have characterized themselves—have advanced a particularly militant form of non-belief. In best-selling books bearing such titles as "The God Delusion" (Dawkins), "God Is not Great" (Hitchens), "The End of Faith" (Harris) and "Breaking the Spell" (Dennett), they have launched a full-fledged war against religion. The "God hypothesis," they insist, is a scientific conjecture about the nature of the universe...