The study of international politics explores the dynamics at the multilateral, bilateral, regional and global levels of relations between sovereign states. In particular, the division focuses on understanding how countries project their interests through political means, such as the use of military, economic or diplomatic power.
There are several competing theories of international politics. Realism is the most influential and popular school of thought. It assumes that states are rational and self-interested, that the international environment is anarchic (no state knows what other states will do) and that they have a degree of military, economic and diplomatic power they can project in order to further their interests.
Liberalism is an alternative to realism. It recognizes that force can have negative consequences for states and that the United Nations, individuals and private parties play important mediating roles in the international arena, a fact that realists tend to overlook. In addition, liberals believe that states have a strong rational interest in cooperation with other states to further their own interests.
Institutionalism is a hybrid theory that incorporates some of the assumptions of realism with some of the insights of liberalism. By using game theory to understand how states interact with each other, this approach argues that cooperation is possible and that the anarchic nature of the international environment is a myth. This theory also argues that non-state actors are more fundamental to the world’s politics than states and that complex interdependence is more likely than conflict.