William Twining is the Quain Professor of Jurisprudence Emeritus at University College London and a regular Visiting Professor at the University of Miami School of Law. He was a pupil of Karl Llewellyn in 1957–8 and put Llewellyn's very extensive papers in order after his death in 1962. Twining's recent writings include Rethinking Evidence, 2nd edition (2006), General Jurisprudence (2009) and How to Do Things with Rules, 5th edition (with David Miers, 2010), all published by Cambridge University Press and recognizable as part of the realist tradition.
'In offering in the afterword new and important historical data along with crisp and challengeable claims about the nature of legal theory as it is practised today, Twining has combined the historical with the jurisprudential in a way that is both faithful to the original book and that makes the book and its new afterword required reading for all those who wish to understand Karl Llewellyn, Legal Realism, American legal thought, and the nature of law itself.' Fred Schauer, from the Foreword