Theory of International Politics created a "scientific revolution" in international relations, starting two major debates. It defined the 1980s controversy between the 'neorealists,' who believed that competition between states was inevitable, and the 'neoliberals,' who believed that states could co-operate. With the end of the Cold War in the 1990s, a second, more fundamental, debate began: Is it possible to treat international relations as a science? Waltz argued that it hardly matters what political system a country has; they all act similarly when it comes to foreign policy. Uniquely, Waltz chose not to look at any single unit within the system; instead, he examined the system itself.