Realism maintains that universal moral principles cannot be applied to the actions of states in their abstract universal formulation, but that they must be filtered through the concrete circumstances of time and place. The individual may say for himself: "Fiat justitia, pereat mundus (Let justice be done, even if the world perish)", but the state has no right to say so in the name of those who are in its care.
The history of modern political thought is the story of a contest between two schools that differ fundamentally in their conceptions of the human nature of man, society, and politics. One believes that a rational and moral political order, derived from universally valid abstact principles, can be achieved here and now. It assumes the essential goodness and infinite malleability of human nature, and blames the failure of the social order to measure up to the rational standards on the lack of knowledge and understanding, obsolescent social institutions, or the depravity of certain isolated individuals or groups. It trusts in education, reform, and the sporadic use of force to remedy these defects. The other school believes that the world, imperfect as it is from the rational point of view, is the result of forces inherent in human nature. To improve the world one must work with those forces, not against them. This being inherently a world of opposing interests and of conflict among, moral principles can never be fully realized, but must at best be approximated through the ever temporary balancing of interests and the ever precarious settlement of conflicts. This school, then, sees in a system of checks and balances a universal principles for all pluralist societies. It appeals to historic precedent rather than to abstract principles, and aims at the realization of the lesser evil rather than of the absolute good.
(Læs endvidere: Six Principles of Political Realism)
Politics Among Nations, 5. udg.. New York.1973. Læs mere om H. Morgenthau >