Hermann Heller was one of the leading public lawyers and legal and political theorists of the Weimar era. However, he is hardly known outside of Germany, in large part because he, a Jewish socialist and militant opponent of the Nazis, died in exile in Spain in 1933 aged 42. He was then in the midst of composing a definitive statement of his views, a book on state theory, which was subsequently published in a form revised by his assistant. Sovereignty is the major work that Heller himself brought to completion. David Dyzenhaus is a professor of Law and Philosophy at the University of Toronto, and a Fellow of the Royal Society of Canada. He holds the Alfred Abel Chair of Law and was appointed in 2015 to the rank of University Professor. He has taught in South Africa, England, Canada, Singapore, New Zealand, Hungary, Mexico and the USA. He holds a doctorate from Oxford University and law and undergraduate degrees from the University of the Witwatersrand, South Africa. In 2002, he was the Law Foundation Visiting Fellow in the Faculty of Law, University of Auckland. In 2005-06 he was Herbert Smith Visiting Professor in the Cambridge Law Faculty and a Senior Scholar of Pembroke College, Cambridge. In 2014-15, he was the Arthur Goodhart Visiting Professor in Legal Science in Cambridge. In 2016-17 he was a Fellow of the Wissenschaftskolleg zu Berlin.