The present volume is a collection of essays and lectures by Dewey B. Larson, arranged and adapted to serve as an introduction to the Reciprocal System of Theory that he originated. It fills an urgent need, since those encountering the theory for the first time may feel overwhelmed by the novelty of its concepts and discouraged by its unfamiliar terminology. The book opens with a critique of the current state of physical theory and its methods, continues by laying a new foundation on which a general and consistent theory of physics can be built, and culminates with a stupendous expedition to the outer reaches of the physical universe and beyond.