Multi-author volume on the history and philosophy of physics.Quantum field theory is a powerful language for the description of the laws and principles that govern the behaviour of the subatomic entities. This book contains up-to-date, in-depth analyses, by a group of eminent physicists and philosophers of science, of our present understanding of its conceptual foundations and their possible revisions.Quantum field theory is a powerful language for the description of the laws and principles that govern the behaviour of the subatomic entities. This book contains up-to-date, in-depth analyses, by a group of eminent physicists and philosophers of science, of our present understanding of its conceptual foundations and their possible revisions.Quantum field theory is a powerful language for the description of the subatomic constituents of the physical world and the laws and principles that govern them. This book contains up-to-date in-depth analyses, by a group of eminent physicists and philosophers of science, of our present understanding of its conceptual foundations, of the reasons why this understanding has to be revised so that the theory can go further, and of possible directions in which revisions may be promising and productive. These analyses will be of interest to graduate students and research workers in physics who want to know about the foundational problems of their subject. The book will also be of interest to professional philosophers, historians and sociologists of science, because it contains much material for metaphysical and methodological reflections, for historical and cultural analyses, and for sociological analyses of the way in which various factors contribute to the way the foundations are revised.Introduction: Conceptual issues in quantum field theory; Part I. Philosophers' Interests in Quantum Field Theory: 1. Why are we philosophers interested in quantum field theory; 2. Quantum field theory and the philosopher; Part II. Three Approaches to tl3/