This book has grown out of my doctoral thesis and has benefitted greatly from the guidance I have received from a number of people. David Miller supervised the original thesis with considerable care, patience and open-mindedness; he later recommended revisions to the manuscript which gave it a clearer structure. G. A. Cohen and Russell Keat examined the thesis and provided me with invaluable comments that helped to determine the shape and content of the book it has become.

Others have been kind enough to comment upon individual chapters at various stages of development. I would like to thank Luc Bovens, Diemut Bubeck, Roger Crisp, Paul Gilbert, Jean Grimshaw, Martina Herrmann, Dan Isaacson, John Kenyon, Kristjan Kristjansson, Kathleen Lennon, Sabina Lovibond, William Lucy, Dugald Owen, Patsy Stoneman, Erik Swyngedouw, Rob Waldie, Nick Wheeler, Andrew Williams and Gavin Williams, for giving me the benefit of their judgement.

I am also grateful to the British Academy, who enabled me to spend time revising the material by awarding me one of their Postdoctoral Fellowships, and to the Master and Fellows at that time of St Peter's College, Oxford, who provided me with a congenial working environment whilst I was holding it. My final thanks are to Lynn Thomas, who I came to know towards the end of writing my thesis, and since then whose encouragement and friendship have been vital to the progress of my research.