How did our forebears begin to think about religion as a distinct domain, separate from other activities that were once inseparable from it? Starting at the birth of Christianity—a religion inextricably bound to Western thought—the Pulitzer Prize-winning author of God: A Biography reveals how the West's "common sense" understanding of religion emerged and then changed as insular Europe discovered the rest of the world. Bringing the story to the present day, Jack Miles shows how this change has played out in the lives of both believers and nonbelievers.