Which of the following is NOT a main theory of international relations?

The correct answer for which option is NOT a main theory of international relations is Modernism. In the field of international relations, the predominant theories include Realism, Liberalism, and Constructivism.

Realism emphasizes the competitive and conflictual side of international relations, focusing on state power and national interests. Liberalism, on the other hand, highlights cooperation between states, the importance of international institutions, and the role of democracy and economic interdependence. Constructivism introduces the idea that social constructs and the identities of states shape international relations and can lead to changes in perspectives and behaviors over time.

Modernism, while it may be relevant in discussions of cultural or philosophical movements, does not stand as a foundational theory within the discipline of international relations. Thus, it is not recognized alongside the established theories like Realism, Liberalism, and Constructivism that provide various lenses through which to analyze global politics and interactions among states.