Like the first edition, which it replaces, this volume is inspired by two great questions: "How does the brain work?" and "How can we build intelligent machines?" As in the first edition, the heart of the book is a set of close to 300 articles in Part III which cover the whole spectrum of Brain Theory and Neural Networks. To help readers orient themselves with respect to this cornucopia, I have written Part I to provide the elementary background on the modeling of both brains and biological and artificial neural networks, and Part II to provide a series of road maps to help readers interested in a particular topic steer through the Part III articles on that topic. More on the motivation and structure of the book can be found in the Preface to the First Edition, which is reproduced after this. I also recommend reading the section "How to Use This Book"-one reader of the first edition who did not do so failed to realize that the articles in Part III were in alphabetical order, or that the Contributors list lets one locate each article written by a given author.