The purpose of this book, originally published in 1987, was to contribute to the advance of artificial intelligence (AI) by clarifying and removing the major sources of philosophical confusion at the time which continued to preoccupy scientists and thereby impede research. Unlike the vast majority of philosophical critiques of AI, however, each of the authors in this volume has made a serious attempt to come to terms with the scientific theories that have been developed, rather than attacking superficial `straw men' which bear scant resemblance to the complex theories that have been...