Why do policies persist even when they produce consistently counterproductive results? When and why do they eventually change, and how does such change occur? The hypothesis explored here is that beliefs are a key intervening variable which shape foreign policy by defining the situation and the range of politically legitimate positions and priorities. This article traces the evolution of Soviet foreign policy beliefs, and suggests that a belief system approach provides a useful alternative to rational actor and domestic political theories for explaining the pattern of continuity and change in Soviet policy. The central argument is that the stability of core beliefs placed limits on the kinds of options available to policy-makers. Beliefs affected domestic politics and foreign policy by influencing the coalition-building process: coalitions which espoused platforms compatible with the requirements of the belief system had a powerful advantage over those which did not. Therefore, despite contradictory goals and problematic results, Soviet foreign policy remained essentially unchanged until Gorbachev, by which time failures in domestic and international performance combined to delegitimize prevailing beliefs. Only then, and only as mediated by a shift at the core level of the belief system, did Soviet policy depart from its traditional goals. Prior to Gorbachev, certain basic patterns in Soviet foreign policy had persevered almost intact from Stalin's time. This was true of Soviet high-handedness and interference in the affairs of other socialist states, opportunistic expansionism in the Third World, and the dual-track nature of Moscow's policy toward the capitalist West. The results consistently undercut Soviet security and prevented the pursuit of a more advantageous realpolitik. The puzzle is twofold. First, despite counterproductive outcomes, such tendencies stubbornly persisted. Second, when change finally did occur, under Gorbachev, it took the form of an abrupt, dramatic shift in every area: toward the West, Eastern Europe, China, and the Third World alike. This article addresses the following questions: first,