Apart from the Introduction, all of the chapters in this book were originally presented as papers at an Intercollegiate seminar at the London School of Economics in the summer of 1980. In soliciting contributions we were aiming at a wide ethnographic spread; but we decided to confine ourselves to our London colleagues so that all the contributors would be able to attend regularly and discuss each other's papers. (Only one of the papers delivered at the seminar – that by Dr S. Humphreys – could unfortunately not be included in the present volume as it was already committed elsewhere.) Our collaboration was continued at a one-day meeting which brought the contributors together before they submitted their final drafts. Though this does not mean that we all share a single point of view, it does mean that all the papers were revised with the others in mind and with the benefit of comments and suggestions from fellow contributors. We hope that as a result this volume will display a unity not always found in collected works of this sort.