Available for the first time in paperback The Quantum Theory of Fields is a self-contained comprehensive & up-to-date introduction to quantum field theory from Nobel Laureate Steven Weinberg Volume I introduces the foundations of quantum field theory The development is fresh & logical throughout with each step carefully motivated by what has gone before After a brief historical outline the book begins with the principles of relativity & quantum mechanics & the properties of particles that follow Quantum field theory emerges from this as a natural consequence The classic calculations of quantum electrodynamics are presented in a thoroughly modern way showing the use of path integrals & dimensional regularization It contains much original material & is peppered with examples & insights drawn from the author's experience as a leader of elementary particle research Exercises are included at the end of each chapter