When people think seriously, they think abstractly; they conjure up simplified pictures of reality called concepts, theories, models, paradigms. Without such intellectual constructs, there is, William James said, only "a bloomin' buzzin' confusion." Intellectual and scientific advance, as Thomas Kuhn showed in his classic The Structure of Scientific Revolutions, consists of the displacement of one paradigm, which has become increasingly incapable of explaining new or newly discovered facts, by a new paradigm that accounts for those facts in a more satisfactory fashion. "To be accepted as a paradigm," Kuhn wrote, "a theory must seem better than its competitors, but it need not, and in fact never does, explain all the facts with which it can be confronted."
For 40 years students and practitioners of international relations thought and acted in terms of a highly simplified but very useful picture of world affairs, the Cold War paradigm. The world was divided between one group of relatively wealthy and mostly democratic societies, led by the United States, engaged in a pervasive ideological, political, economic, and, at times, military conflict with another group of somewhat poorer, communist societies led by the Soviet Union. Much of this conflict occurred in the Third World outside of these two camps, composed of countries which often were poor, lacked political stability, were recently independent and claimed to be nonaligned. The Cold War paradigm could not account for everything that went on in world politics. There were many anomalies, to use Kuhn's term, and at times the paradigm blinded scholars and statesmen to major developments, such as the Sino-Soviet split. Yet as a simple model of global politics, it accounted for more important phenomena than any of its rivals; it was an indispensable starting point for thinking about international affairs; it came to be almost universally accepted; and it shaped