Hans Kelsen (1881–1973)

Hans Kelsen was a Viennese legal theorist and constitutional and international lawyer of Jewish background who is often described as the most important legal mind of the twentieth century. His chief work was Die Reine Rechtslehre [The Pure Theory of Law], first published in 1934. The purity of jurisprudential method postulated in it, understood as a “scientific” positivism, was a fundamental critique of the voluntaristic positivism [Staatswillenspositivismus] that dominated the public-law mainstream in the German Empire, and simultaneously a radicalized response to the opening, at the beginning of the twentieth century, of public-law scholarship to the young disciplines of sociology and psychology. Kelsen himself, however, was not only a constitutional and international lawyer, but also a legal theorist, legal sociologist, and legal historian. Throughout his life, he championed parliamentary democracy and compulsory constitutional adjudication, which he helped introduce in Austria, as well as the juridification of international relations and their law-based institutionalization.

Kelsen's main work on international law was his 1920 monograph Das Problem der Souveränität und die Theorie des Völkerrechts [The Problem of Sovereignty and the Theory of International Law]. He wrote it during the First World War in a historical phase when the pacifist-liberal current in Europe and the United States regarded the inadequate institutionalization of the international legal system, including compulsory jurisdiction, as the chief reason for the outbreak of the war. Kelsen shared this view.