Abstract
International relations have always been characterized by wars, peace and alliances. The question that theorists wonder is why interactions between States sometimes degenerated into conflicts which change relations between them. There are three main theories in international relations which attempt to understand the behavior of states in international politics: realism, institutionalism and the state-society approach. State is defined by M. Weber as ‘a human community that (successfully) claims the monopoly of legitimate use of physical force within a given territory' (Gerth and Wright Mills, 1946).
The three theories share a number of assumptions about the way states interact in international politics. They all consider that States are the main actors in an anarchic system (although they do not have all the same conception of what is anarchy). These states are rationalist and egoist, following their own interests. Finally, all the theories include the idea that there are generalizable and positive causal explanations to international outcomes. On the other hand, these theories differ on many points, especially about the importance of domestic politics.
Hence, one may wonder if knowing the internal politics is sufficient to understand how states behave in international politics. We will demonstrate that none of the three main theories consider that this sufficient and that we cannot disregard external environment to understand international behaviors, although it is obvious that the State-society approach attaches much more importance to this factor than realists and institutionalists.
