This text develops quantum theory from its basic assumptions, beginning with statics, followed by dynamics and details of applications and the needed computational techniques.; The discussion is based on the view that the fundamental entities of the universe are not particles but fields, with the observed particles arising as their quanta.; Quantum fields are thus introduced from the beginning, with a discussion of how they produce quanta that manifest themselves as particles.; Most of the book, of course, deals with particle systems, as that is where most of the applications lie; the treatment of quantum field theory is confined to fundamental ideas and their consequences.; For developing quantum dynamics, the author uses the Lagrangian technique with the principle of stationary action.; The roots of this approach, which includes generating the canonical commutation rules, go back to a course taught by Julian Schwinger, filtered through many years of the authors own teaching.; The text emphasizes that the wave function does not exist in physical three-dimensional space, but in configuration space, and it points out that the probabilistic features of the theory arise not from a lack of determinism but from the definition of the state of a system, so that many, though not all, of the counterintuitive aspects of quantum mechanics arise from its probabilistic nature and are shared by other probabilistic theories such as classical statistical mechanics.