The Late H.L.A. Hart was Professor of Jurisprudence in the University of Oxford from 1952 to 1968. Subsequently he became Principal of Brasenose College, Oxford. His other major works include Causation in the Law (with Tony Honore, OUP 1959), The Concept of Law (OUP 1961) and Law, Liberty and Morality (OUP 1963). ; John Gardner has been Professor of Jurisprudence in the University of Oxford since 2000. He is a former Fellow of All Souls and Brasenose Colleges in Oxford, and has also taught at King's College London, Yale Law School, Columbia Law School, and the University of Texas. His book Offences and Defences is forthcoming from OUP.