Kant, Immanuel (1724–1804)

Some contemporary philosophers consider Immanuel Kant the most influential philosopher of law of modern times. Although he was not trained as a jurist, he regularly lectured on natural law throughout his career, and he was familiar with both legal terminology and legal reasoning. His most extensive discussion of law is to be found in the first half of his Metaphysics of Morals. This work, published in 1797, has often been dismissed as a product of Kant's old age, and it certainly lacks the philosophical depth of the writings of his prime. Nevertheless, when one adds to it the Groundwork of the Metaphysics of Morals(1785), the Critique of Practical Reason(rev. 2d ed. 1788), and a series of Kant's shorter works on political and legal topics, they comprise a considerable body of writing dealing with profound issues in moral, political, and legal theory.

Kant produced most of this writing either shortly before or during the French Revolution, whose outcome (though not whose violence) he welcomed. Part of his importance is historical: his theory of the republican state, based on individual rights, the separation of powers, and the elimination of hereditary privilege, marks the start of the liberal nineteenth-century theory of the Rechtsstaat (that is, the state based on the rule of law). It also both sums up Enlightenment thinking on politics and, in its emphasis (derived from Jean-Jacques Rousseau, 1712–1778) on individual autonomy, points forward to some of the characteristic themes of Romantic political thought.

But Kant's deeper importance is philosophical. His moral and legal theory rests on a radical demand that ethics be universal and necessary—that it apply, not just contingently to all human beings, but necessarily to all rational agents whatsoever. This means that ethics at its core must be a priori—not in the sense that empirical information is irrelevant to determining what we are to do, but in the sense that the most fundamental principles of morality cannot be derived from experience.

This demand for an a priori foundation Kant ties to the second great metaphysical theme of his moral philosophy: its emphasis on autonomy, on the freedom of the will. For at bottom, the a priori character of the moral law is deeply connected to its status as a law that can be viewed as expressive of rationality, and thus as being in a certain sense given by rational agents to themselves. Kant's radical a priorism knocks away the classical theories of the foundations of politics. The state can no longer ultimately be justified by appeal to tradition, or human nature, or experience, or even brute divine commands: for these things are insufficiently a priori. In The Science of Right(1790), Kant argued that a purely empirical science of law is like a wooden head; it may be beautiful, but it unfortunately lacks a brain.

Kant's writings on law attempted to work out the consequences of taking the categorical imperative as the ultimate foundation for the legal system, and he [Page 876]carried the analysis into the law of contract, of property, and of punishment, as well as into international law. His writings provided the starting point for the legal philosophies of Johann Fichte (1762–1814) and of Georg Wilhelm Hegel (1770–1831) in the nineteenth century, and strongly influenced the work of Hans Kelsen (1881–1973) and John Rawls (1921–2002) in the twentieth.

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