In his search for a valid theory of international relations, Gilpin explores economic, sociological and political approaches and finds the essence of the international system, throughout history, in an ever-changing equilibrium threatened by the uneven growth of power among states. The book is rich in the use of history and the breadth of its analysis and it breaks some new ground. It is, also, an academic study written for academics; the general reader, though he may need to absorb its lessons, will find it rather hard going.