The balance of power is the oldest and most invoked idea in the study of international relations. The rivalries of ancient city-states and modern great powers alike would be difficult to understand without it. The end of the Cold War, however, ushered in an era of U.S. dominance in which traditional great-power balancing has been noticeably absent -- and so scholars are again debating the idea's merits. This book, by a distinguished British scholar, provides a welcome intellectual history of the many uses and meanings of the term "balance of power." What Little finds most striking is the variation in how the logic of balancing has been understood. To some, power balancing was the inevitable and conflict-ridden byproduct of anarchy and insecurity; to others, it was the unifying principle of a stable and cooperative international society. Little spends most of the book examining the balance-of-power ideas of four leading postwar realist scholars: Hans Morgenthau, Hedley Bull, Kenneth Waltz, and John Mearsheimer. He tries to assemble a composite theory, but this is less interesting than his overall message: the balance of power is not an immutable law of nature so much as a way of thinking about the world.