Hans Kelsen was born in Prague towards the end of the nineteenth century. He finished high school(gymnasium) in Vienna with the general qualifications for university entrance (Matura). Studied at the Universityof Vienna, where he obrained his doctor’s degree, made his habilitation (qualification for teaching asdocent) and later was pointed Professor there.He was influential in the constitutional development of Austria from the monarchy to the republic and byhis methodology (self-styled “Pure theory of Law”) had a strong positivistic impact on the legal thinking inthe twentieth century.Kelsen was a legal scholar who passed from legal philosophy through the doctrine of state and law to internationallegal doctrine. He laid the basis for the judicial review of laws, regulations and other legal acts bya constitutional court. The political situation of the nineteen thirties and forties caused him to be on a constantmove. He taught law consecutively in Vienna, Cologne, Prague, Geneva, Harvard and Berkeley.