Classical Realism is a theory of International Relations established in the post-World War II era that seeks to explain international politics as a result of human nature. The theory is asociated with thinkers such as Niccolò Machiavelli and Thomas Hobbes. Modern thinkers associated with classical realism are Carl von Clausewitz, Hans Morgenthau and Reinhold Niebuhr. Classical Realist thought has since been overshadowed by Neorealism after Kenneth Waltz' work became more widely accepted due to the rise of Structuralism in North American International Relations scholarship which favored the latter's emphasis on rationality rather than human nature as cause for political conflict.
Order is a main focus of Classical Realism. Classical Realists argue that order is fragile and created through constant tensions between state nations. Related to this argument is the theory of human reshaping. Human reshaping puts forth that the world can become a 'better' place through incremental changes made by humans through enlightened self interest. Humans can change their environments only through much difficulty and slowly.
Hans Morgenthau wrote in his 1948 work Politics Among Nations that "politics is governed by objective laws that have their roots in human nature." Human nature is inherently flawed, therefore conflict occurs as a natural outcome of conflicting nations' search for power. Morgenthau argues that since politics is governed by the objectivity of human nature, a theory of international relations can be developed by placing oneself in the position of the statesman in order to predict political outcomes.