International Relations Theories Realism, Idealism, and Marxism-Leninism There are three major theories concerning the behavior of states in international relations; Realism, Idealism, and Marxism-Leninism. Realists believe in the concept of power and conflict, spurning suspiciously the idealistic view that moral principles and international law should be used to govern international politics. Idealists are in favor of a reliance on international organizations to be used as tools to promote the development of democracy in the world, eliminating the threat of war because history shows that democr