Waltz, Kenneth. “Realist Thought and Neorealist Theory”. Journal of International Affairs, Vol.44, No.1 (1990): 21-37.

Waltz, Kenneth. “Realist Thought and Neorealist Theory”. Journal of International Affairs, Vol.44, No.1 (1990): 21-37.

• The author credits the distinction between explanation and theory in economics as the successful separation of the economy into its own field of study separate from society and the state. While recognizing that this difference is artificial, the author contests that this artificial division and ignoring certain factors is necessary for constructing theory (22).
• The first breakthrough in European economics from observation to theory was undertaken by Francois Quesnay, the founder of an intellectual tradition in economics called the Physiocrats. Mr. Quesnay developed a -- incorrect -- theory explaining all economic activity (23-24).
• Hans Morgenthau and Raymond Aron, two major theorists in the realist school of IR, both argued that the division between society and the economy engineered by the physiocrats would be impossible in IR because the motivations of states are so complex that a clear domestic-international distinction is impossible, no dependent variables can be controlled for, and too many variables are present to make accurate predictions (24-26).
• The author contests all of Dr. Aron's reasons that IR cannot be theorized. First, complexity requires theory to radically oversimplify the world so that it can be sort-of explained and predicted with some accuracy, even if it ignores most detail. Secondly, although the real world doesn't have dependent variables, making partially false assumptions for the purpose of theorizing can provide those variables (27). 
• Neorealism solves these theoretical problems by delineating a specifically international field of study, based on a self-help structure (29).
• The lack of measurement in IR also does not preclude theories of IR. Many major economic theorists, like Adam Smith, never or rarely use numbers in their theories, instead using general concepts. This means that lack of measurement is also not an impediment to theorizing in IR (28). 
• Some scholars, like Robert Keohane and Barry Buzan, object to the claims by neorealism to explain IR; they contest that many important variables, like international institutions, are left out of the theory. The author dismisses these concerns are too difficult to incorporate into a single theory, and the theory is good enough anyway, so they can be left out (30-31).
• Similarly, major factors like ideological divides or different types of governments are important, but are both less important than power differentials and are affected by power differentials. Therefore, it is still okay to have a theory in which power balances in an anarchic system are the only explanatory factor (31).
• Neorealism is different from realism in IR theory because it justifies the world order on the basis of international anarchy rather than human avarice, defines power differently, and treats states differently (32):
• The realist school of IR bases its theory on the interactions between states, varying on the basis of the strengths and motivations of those states. Neorealism argues that this view must be supplemented by the structural factors of international anarchy, which compels states to behave in certain ways separate from the motivations of individuals states or actors (33).
• The author argues that the superiority of neorealism is shown through the inability to realism to explain why wars occur between all possible government types with ever kind of reason or motivation. The solution is that wars are not common because of greed, but anarchy makes them likely (34).
• Realism looks at power as the primary motivation for state action and an end goal, with its basis on a natural human lust for power. Neorealism, on the other hand, see power only a means to accomplish the end goal of survival (35-36).
• Realism still requires some knowledge of domestic politics to understand how different states will behave. By reducing all state motivation to survival under self-help conditions, neorealism removes the need to know anything about domestic politics, creating total separate studies of IR and politics (36-37).