This book, first published in 1989, gives a critical account of formal international relations theory. That formal and mathematical methods can be applied to the study of international relations is often regarded with surprise, but the author demonstrates not only how these methods give insights into problems such as deterrence or arms races but also that the increase in the power of explanatory tools depends on the more rigourous development of theory along these lines. Mathematical methods have been applied to the study of international behaviour since the pioneering work of Lewis Fry Richardson in the 1920s and 1930s. However, it was in the post Second World War period that they became widespread. Dr Nicholson discusses the application of such methods as the theory of games to problems of relationships between states, catastrophe theory to the study of initiation of violence, and probability theory to the question of the probability of nuclear war.