This book provides an introductory survey of the evolution of Realism in international theory. It is the first book to examine the history of Realism in terms of its own evolution as a paradigm, rather than providing a survey of some of the key Realist thinkers, and the first book to include a detailed consideration of the IPE dimension of Realism. Guzzini argues that any account of the historical evolution of theory must be concerned with both internal history - the intra-theoretical developments, refinements and rebuttals of existing approaches that have shaped IR and IPE, and with external history - including both the intellectual environment within which theories are constructed and the external history of the subject matter including real developments in international affairs. It is the exchange between these two histories that forms the subject of this book. Guzzini contends that as the leading school of thought of the discipline, Realism is the reference point of the internal history of IR and IPE. A study of the development of the realist paradigm is thus the key to an understanding of international history.