Abstract

This chapter examines the realist tradition in international relations (IR), which is best seen as a research programme with several approaches using a common starting point. It highlights an important dichotomy in realist thought between classical realism and contemporary realism, including strategic and structural approaches. After describing the elements of realism, the chapter discusses the international thought of three outstanding classical realists of the past: Thucydides, Niccolò Machiavelli, and Thomas Hobbes. It then analyses the classical realist thought of Hans J. Morgenthau, along with strategic realism, neorealism, and neoclassical realism. Special attention is devoted to the defensive realism of Kenneth Waltz and the offensive realism of John Mearsheimer. Furthermore, the chapter looks at the recent theoretical debate among realist IR scholars concerning the relevance of the balance of power concept and it shows that realists often disagree among themselves. The chapter concludes with an overview of how the different realist theories treat international and domestic factors.