Naturalism is widely regarded as the dominant philosophical worldview in the West. The prestige of science and the power of technology have driven naturalism to prominence, even as deep questions mount on all sides. In this volume of all new essays, prominent philosophers consider a wide variety of challenges to naturalism, proposing improved defenses and novel developments in this influential worldview. Some essays question whether naturalism is a unified philosophy, and try to determine how one or another variety of naturalism has an advantage. Other essays defend naturalism's approaches to religion, the mind, experience, morality, and society. To ensure that naturalism has a strong future, this volume's authors are determined to help reformulate its principles for the 21st century. Among the contributors are Mario Bunge (McGill University), Paul Kurtz (Center for Inquiry and State University of New York at Buffalo), John Lachs (Vanderbilt University), Isaac Levi (Columbia University), Joseph Margolis (Temple University), Nicholas Rescher (University of Pittsburgh), John R. Shook (Center for Inquiry), and other leading philosophers.