In The Quantum Theory of Fields Nobel Laureate Steven Weinberg combines his exceptional physical insight with his gift for clear exposition to provide a comprehensive and up-to-date introduction to quantum field theory. Volume II gives a fresh and logical account of the methods of quantum field theory, and how they have led to an understanding of the weak, strong, and electromagnetic interactions of the elementary particles. Modern mathematical methods are interwoven with accounts of the problems of elementary particle physics and condensed matter physics. It includes topics not usually found in books on quantum field theory, such as the Batalin-Vilkovisky formalism and its application to renormalization and anomalies in gauge theories; the background field method; the effective field theory approach to symmetry breaking; critical phenomena; and superconductivity. Intended for graduate students in physics and mathematics, the book contains much original material, and is peppered with examples and insights from the author's experience as a leader of elementary particle physics. Problems are included at the end of each chapter.