Physicalism has over the past twenty years become almost an orthodoxy, especially in the philosophy of mind. Many philosophers, however, feel uneasy about this development, and this volume is intended as a collective response to it. Together these papers, written by philosophers from Britain, the United States, and Australasia, show that physicalism faces enormous problems in every area in which it is discussed. The contributors not only investigate the well-known difficulties that physicalism has in accommodating sensory consciousness, but also bring out its inadequacies in dealing with thought, intentionality, abstract objects (such as numbers), and principles of both theoretical and practical reason; even its ability to cope with the physical world itself is called into question. Both strong 'reductionist' versions and weaker 'supervenience' theories are discussed and found to face different but equally formidable obstacles. The impression with which these essays leave the reader is that the advance of physicalism has been achieved more by talking down the problems that face it than by solving them.