Philosophers and economists rarely find much common ground, and we gave the seminar, which fathered this book, with more curiosity than confidence. The results were a welcome surprise, and subsequent discussions with colleagues have helped to trace further philosophical threads in the web of orthodox economic theory. In a sense the book is a tribute to the hopes of the Oxford P.P.E. school, through which we have both passed. Admittedly Hollis has only hazy recollections of genial hours with his economics tutors, but Nell is the author of several philosophical papers and has contributed much more than the economics here, for which he takes sole praise or blame. Hollis is responsible for the main philosophical argument (and also for the prose in which most of the final draft has been couched). Nevertheless, at least on the philosophical side, we regard the text as a genuinely cooperative effort.

Our thanks are due to many colleagues for their invaluable criticisms of earlier drafts. In particular, we would like to mention Dr Onora Nell of Barnard College, Professors Adolph Lowe and Robert Heilbroner of the New School, New York; Robert Sutcliffe of Oxford University and David Bailey, Bryan Heading, Peter Townroe and Professor Harold Lydall of the University of East Anglia; and the nameless readers of the Cambridge University Press. We gratefully acknowledge, also, the grant which we received from the American Philosophical Society towards the preparation of the book. Finally, our thanks go to Margaret Dunbar for preparing the diagrams and to Martha Stires for assistance in preparing the index.