International political theory - the founder of structural realism (also known as neorealism), also translated as Kenneth Waltz.

Walz believes that for a theory to be scientific, it must reduce variables as much as possible. He divided the structure of the international political system into three constituent principles: the principle of arrangement of the system, the principle of functional differentiation of units, and the principle of power distribution among units in the system.

Walz believes that, first of all, domestic politics and international politics are different. In domestic politics, units are grouped together in a hierarchical manner. In international politics, units have sovereign equal status, and the ordering principle is anarchic order. Therefore, he advocated treating domestic politics and international politics as two separate fields based on the density of interaction. Secondly, although countries have differences in culture, ideological fields or systems, their basic functions are similar, that is, they all perform the same responsibilities, such as collecting taxes, promoting foreign policies, etc. Third, even if political differences and conflicts occur within a country, they can ultimately be resolved authoritatively domestically. Finally, starting from structure, the structure of the international system severely limits the behavior of great powers and forces them to act in the same way.