Book excerpt: An argument for the classical realist approach to world politics An Unwritten Future offers a fresh reassessment of classical realism, an enduring approach to understanding crucial events in the international political arena. Jonathan Kirshner identifies the fundamental flaws of classical realism’s would-be successors and shows how this older, more nuanced and sophisticated method for studying world politics better explains the formative events of the past. Kirshner also reveals how this approach is ideally equipped to comprehend the vital questions of the present—such as the implications of China’s rise, the ways that social and economic change alter the balance of power and the nature of international conflict, and the consequences of the end of the US-led postwar order for the future of world politics. Laying out realism’s core principles, Kirshner discusses the contributions of the perspective’s key thinkers, including Thucydides, Hans Morgenthau, and Raymond Aron, among others. He illustrates how a classical realist approach gives new insights into major upheavals of the twentieth century, such as Britain’s appeasement of Nazi Germany and America’s ruinous involvement in Vietnam. Kirshner also addresses realism’s limits and explores contemporary issues, including the ascent of great power challengers, the political implications of globalization, and the diffusion of power in modern world politics. A reexamination of the realist tradition, with a renewed emphasis on the crucial roles played by uncertainty, contingency, and contestation, An Unwritten Future demonstrates how a once-popular school of thought provides invaluable insights into pressing real-world problems.