This book is based upon a doctoral thesis of the same title presented to the University of Cambridge in May 1975. In preparing it for a wider readership, I have omitted two chapters that bore less directly on the central theme and have further revised parts of the remainder. I am deeply grateful to the trustees of the Tyrwhitt Hebrew Fund and the managers of the Hort Memorial Fund for generous grants to assist in its publication.

It is hoped that the references given in the footnotes, though abbreviated, will be sufficient for readers conversant with the field to recognize at once the book or article cited. In addition, a full bibliography of works referred to is supplied on pages 141–54, so that there should be no difficulty in ascertaining a complete reference where required. It should further be noted that books cited by their author's name alone are also included in the list of abbreviations. Citations of the Hebrew Bible are taken from the third edition of Biblia Hebraica, edited by R. Kittel (Stuttgart: 1937). Unless otherwise stated, the English translation of the Bible is that of the Revised Version (1884). The Loeb Classical Library is used for the text, translation and system of reference for all classical authors (including Josephus).