Slaughter, Anne-Marie. "International Relations, Principles Theories" In Max Planck Encyclopedia of Public International Law, edited by R. Wolfram. Oxford: Oxford UP, 2011.

Slaughter, Anne-Marie. "International Relations, Principles Theories" In Max Planck Encyclopedia of Public International Law, edited by R. Wolfram. Oxford: Oxford UP, 2011.

• In Realist IR theory, referring to Neorealism, states are entirely autonomous and exist in an anarchic system in which international order cannot, by definition, exist. States are bound only by coercion or their own consent ( ¶ 2).
• Based on Dr. Mearsheimer, Realist IR theory assumes that states can foremost about their own survival, cannot assume what their neighbor may do, states are rational actors, and that great powers are defined by measurable military and economic strength ( ¶ 4).
• Realists diverge on the desirability of hegemony in an international system. Offensive Realists, like Dr. Mearsheimer, argue that states will constantly desire more relative power, leading to hegemony. Defensive Realist on the other hand, like Dr. Waltz, argue that creating hegemony creates so many conflicts that states will actually create balance of power systems to avoid those devastating conflicts (¶ 5).
• Realists claim that international law and associated institutions are a effect of power relations, but do not affect power relations in any meaningful way. They do not shape state behavior, only clarify what states were already going to do     ( ¶ 6-7).
• Institutionalist IR theory shares many assumptions with the Realist school, but believes that cooperation between states is actually possible ( ¶ 8).
• According to Institutionalists, like Dr. Keohane, international institutions work because they turn a single interaction into a series of games in which interactions with other states can be understood. The institutions constructed lower the costs of interaction by regularizing it, increase the penalties for cheating by establishing rules and watchdogs, and makes sure that deals between nations are transparent ( ¶ 10-13).
• Liberal IR theory is a diverse field brought together by beliefs that the domestic conditions of states affect their international relations. This theory is most pronounced in assumptions about the nature of liberal democracies. It explains a number of behaviors because it allows for group and individual interests to effect state interests, meaning they do not have to be purely rational actors ( ¶ 14, 17).
• Constructivism is not really a theory, but an ontology within IR that spawned a number of sub-theories. Constructivists, like Dr. Wendt, argue that objects in IR are not important in themselves, but because of the social value constructed for them; the classic example being the different meanings of the Chinese and British nuclear arsenals ( ¶ 19-20).
• Various Constructivist scholars have contributed important theories, and many believe that states are not unitary rational actors ( ¶ 21). Drs. Keck and Sinkkink are pioneered work on the roles of NGOs and private interests ( ¶ 23), and Drs. March and Olsen demonstrated the importance of international norms ( ¶ 22).
• The English School of IR theory is based on historical studies of international order and not interested in contemporary theory. Instead, people like Dr. Hedley Bull, argue that a range of factors all influence international politics, those factors change, and that historical depth is needed to understand contemporary IR ( ¶ 24-25).
• "While many theories of international relations are fiercely contested, it is usually inappropriate to see them as rivals over some universal truth about world politics. Rather, each rests on certain assumptions and epistemologies, is constrained within certain specified conditions, and pursues its own analytic goal. While various theories may lead to more or less compelling conclusions about international relations, none is definitively ‘right’ or ‘wrong’. Rather, each possesses some tools that can be of use to students of international politics in examining and analyzing rich, multi-causal phenomena" ( ¶ 28).