Th is book has been written during my tenure of a Leverhulme Major Research Fellowship, 2010–2012, and I am very grateful for the opportunity for uninterrupted research and refl ection that the Fellowship provided. I am indebted to many friends and colleagues for their help and advice during this period, but most especially to John Allison, Peter Cane, David Dyzenhaus, David Feldman, Andrew Hillam, Jeff King, Stuart Lakin, Nick McBride, Alistair Mills, Nigel Simmonds, and Mark Walters for kindly reading and commenting on particular chapters. Andrew Hillam has generously read many chapters and given me invaluable advice on making my text more readily accessible to undergraduates as well as more experienced scholars. I am also grateful to Alex Flach and Natasha Flemming at Oxford University Press for their effi cient and friendly assistance. I have learnt much from the critical literature provoked by my previous writings on constitutional theory and public law. My critics have prompted me to think harder about my own conception of common law constitutionalism (as it is usually called); and I have taken the present opportunity to respond to their objections when it has seemed helpful to do so in order to advance or clarify my argument. My principal aim has been to explore some basic questions of method in the analysis of public law, attempting to lay bare the theoretical grounds of some of the major debates and controversies within the subject. I hope at least to clarify the jurisprudential roots of my own position, in respect of many of these controversies, even if I fail to bring all readers round to my own conclusions.