On the Old Saw: That May Be Right in Theory but It Won't Work in Practice

On the Old Saw: That May Be Right in Theory but It Won't Work in Practice

On the Old Saw: That May Be Right in Theory but It Won't Work in Practice

On the Old Saw: That May Be Right in Theory but It Won't Work in Practice


In this famous essay, first published in 1793, Kant considers the alleged conflict between theory and practice in the conduct of human affairs in three widening contexts: those of the common person faced with a moral decision, of the politician and the citizen concerned with the extent and limits of political obligation, and, finally, of the citizen of the world whose actions have a bearing on war and peace among nations.

Unlike other animals, Kant reminds us, people must decide how they will live their lives. They therefore ask for a guide to action, a set of principles--a theory.

From the outset, Kant rejects the ancient claim that the practical possibilities of action cannot always be reconciled with moral demands. He offers his own moral theory, a theory starting out from the principle of the right as an unequivocal guide to action. In partial disagreement with the rival theories of Hobbes and Locke, he proposes that the only condition under which the individual can achieve true destiny as a person and a member of the human race is the civil state. Such a state can be secured only by law. Although "from such crooked wood as man is made of, nothing perfectly straight can be built," only the rule of law can bring about a stable society.

Last, Kant turns to the relation between theory and practice in international relations. "Nowhere," he writes, "does human nature appear less lovable than in the relation of whole nations to each other." But to hope for world peace on the basis of "the so-called balance of power is a mere chimera." There is no other remedy to international lawlessness and war than an international coercive law, and such law can grow only out of sound theory. "I put my trust in theory. At the same time, I trust in the nature of things, and also take account of human nature, which I cannot, or will not, consider so steeped in evil that in the end reason should not triumph."


Few people are so ignorant that they will dispute the value of theory. Yet men commonly denounce proposals that apply theory in daily life. Many of the finest insights of science, medicine, agriculture, ethics, law, and politics have been summarily rejected with the ritualistic formula: “That may be right in theory, but it won’t work in practice.” Fully appreciative of the enervating and pernicious influence of this nostrum, Kant published in 1793 the most rigorous and sustained critique that it or any other cliché has ever received.

Kant’s essay, addressed to a broad intellectual audience, is one of the most neglected though most important documents of the Enlightenment. It is here published in English as a separate volume for the first time. Its relevance today depends least on its contribution to Kantian studies, though in “Theory and Practice” Kant elaborates significantly on the role of happiness in ethics and provides his clearest discussion of moral feelings and the nature of ethical motivation. Its importance for today derives primarily from Kant’s brilliant discussion of critical political issues that are of intense contemporary interest—the nature of political authority, the right of revolution, freedom of the pen, the authority to make war, and the preservation of peace. Although these issues, raised by Hobbes, Locke and Rousseau, were central to political discussion at the founding of our Republic, their relevance even now is undiminished.

Kant examines the cliché from two general aspects. First, he discusses the problems involved in applying any theory and the paradoxical fact that there are theoreticians who lack the judgment . . .

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