The study of international relations has been dominated by realism for approximately 60 years. Over the course of time, the concept of realism has undergone changes though, which can be classified as a school of classical- and neo-realism.

Originally, realism was born in opposition to a moralistic or even idealistic understanding of interstate relations. The interpretation of human nature is not value-free in classical realism. Instead, an analysis of domestic and international political practice and a comprehensive analysis of human nature are part of classical realism. By dragging a complex analysis of political practice into the concept of realism, the classic model of realism becomes unoperationalizable, at least from the viewpoint of neo-realistic scholars.

For them, classical realism is not scientific enough. Their works are often considered as structural realism, as they focus on a system composed of a structure and interacting units, with the underlying structure being the main feature. During the necessary definition of the structure, characteristics of the units have to be omitted, in order to develop a truly scientific structure. Only structure delivers a clear and fixed outset for the interpretation of interstate relations, according to the authors of neo-realism. They draw parallels to the study of economics, where an ongoing analysis of particular companies or specific transactions is just as omitted and the theory is based on the famous “economic man” and rational markets. Authors as Waltz recognize that the pure “economic man” does not exist, but nevertheless has to exist in order to develop an operationalizable theory, which can be used to find out “what to expect in general”.

Classical realism does not belief in a supposingly more scientific theory embedded in assumptions. By making assumptions as important as neo-realism does, the whole foundation of neo-realism becomes based on stipulation and not ongoing argument, as it should. Human nature and structural consideration are cornerstones of classical realism, whereas neo-realism handles human nature in broad assumptions parallel to the concept of “economic man” and focuses only on the structure.

In classical realism, human nature is not only rational, as it is in neo-realism. A thorough analysis of ongoing human behaviour reveals impulses of honour and profit-seeking that go beyond the structurally motivated fears neo-realism is based upon. Therefore, if realism is understood as a technology to master international relations, it can only be directed towards peace in the sense of a universal empire, a scholar of classical realism concludes. Neo-realism instead favours a rationally limited view of national interests and a rational recognition of an international common good, thus realism as a technology to master international relations becomes an instrument for the reduction of conflict and fostering of global peace. Absolute gains over time are more important than gains relative to other states, a belief that needs very rationalistic assumptions about human nature and that scholars of classical realism would criticise as too abstract and theoretical.

It is interesting to note that neo-realism, which totally focuses on structure and structure alone and omits everything else, especially the characteristics of the units acting within the structures, understands itself as a “science of peace”, or a technology aimed at a “more just and more peaceful world”. Without a doubt, neo-realism does away with moral influences in the construction of its theory, but then results in a moralistically positive outcome. This, once again is supposed to parallel economic markets, where the actors acting towards their own self-interest in a laissez-faire environment nevertheless produce a global result favourable for everyone involved. In my personal opinion, it is definitely possible to argue that the theories of economic man and overall wealth created by perfect markets are, on the one hand, very operationalizable, but on the other hand not worth a lot. With their high degree of scientific rigor they have shifted away from economic reality and are thus, more often than not, far less helpful than their creators intended them to be. The logic of classical realism’s critique of neo-realism seems to follow the same steps.

To conclude, the main difference between classical- and neo-realism is thus the degree of scientific grounding the theories are based upon. Critics of neo-realism state, just as in economical theory, that theories remove themselves more and more from actual reality the more scientific they claim to be. There is no clear right or wrong in this regard, but it seems as if the more operationalizable a theory becomes, the less it will be able to predict future developments, and the less operationalizable or scientific a theory becomes, the more it is attached to reality while at the same time unable to serve as a tool to know what to expect.