This book has evolved from my University of Essex doctoral dissertation. Much of the material has been reorganized, and a number of changes have been introduced, involving the omission of a good deal of background information and the addition of some new material. I have tried, at the same time, to preserve the essential character of the arguments as they originally appeared. I would like to thank a number of people for their help at various stages of (re)writing. Martin Atkinson, Vivian Cook, Michael Jones, and Mark Newson made significant contributions to the development of the dissertation on which this book is based. A special mention must be made of Gillian Brown, Iggy Roca and Keith Brown, who also provided invaluable support during the period of work at Essex. In fact, the help of all these people, in one form or another, has continued to reach me ever since. Furthermore, two anonymous reviewers for the publisher provided very insightful comments, as also did Teun Hoekstra, inducing me to reconsider most of the original arguments and to reformulate quite a few of them. I have also benefited from the information, inspiration and encouragement received from David Lightfoot, Ken Safir, Neil Smith, and Ken Wexler. Needless to say, I take full responsibility for the errors and omissions that may still remain.

The research that eventually led to this volume was carried out while I held a British Council fellowship, and was consequently able to be on leave from my job at the Allama Iqbal Open University.