Discussions of religion are typically about God. Atheists reject religion because they don’t believe in God; Jews, Christians and Muslims take belief in God as fundamental to their religious commitment. The philosopher John Gray, however, has recently been arguing that belief in God should have little or nothing to do with religion. He points out that in many cases — for instance, “polytheism, Hinduism and Buddhism, Daoism and Shinto, many strands of Judaism and some Christian and Muslim traditions” — belief is of little or no importance. Rather, “practice — ritual, meditation, a way of life — is what counts.” He goes on to say that “it’s only religious fundamentalists and ignorant rationalists who think the...