Morgenthau on Realism

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. Both individual and state must judge political action by universal moral principles, such as that of liberty. Yet while the individual has a moral right to sacrifice himself in defense of such a moral principle, the state has no right to let its moral disapprobation of the infringement of liberty get in the way of successful political action, itself inspired by the moral principle of national survival. There can be no political morality without prudence; that is, without consideration of the political consequences of seemingly moral action. Realism, then, considers prudence-the weighing of the consequences of alternative political actions-to be the supreme virtue in politics. Ethics in the abstract judges action by its conformity with the moral law; political ethics judges action by its political consequences. Classical and medieval philosophy knew this, and so did Lincoln when he said:

I do the very best I know how, the very best I can, and I mean to keep doing so until the end. If the end brings me out all right, what is said against me won't amount to anything. If the end brings me out wrong, ten angels swearing I was right would make no difference.