It is surprising to realise that more research has been done on the Fāṭimids than on any other aspect of Islamic history. Conveniently M. Canard has summed up the results of all this research, including his own, in an article of thirteen large and crowded pages in the new edition of the Encyclopaedia of Islam to which he and others have also contributed numerous other relevant articles. Therefore, the basic facts of Fāṭimid history have been well established. Bernard Lewis, who started working on the subject almost forty years ago, has recently given us his interpretation of Fāṭimid history. All these researches have in common one principal weakness; they do not take into consideration earlier developments nor all of the important circumstances in the areas the Fāṭimids controlled. They are also unbalanced in that more has been said about the birth certificate of the first Fāṭimid ruler than about economic conditions in his domains. His genealogy, interesting as it may be, is unimportant because enough people believed in his cause to make possible his rise to power. They also believed his claim to be a descendant of the Prophet through his daughter Fāṭima, a claim which was an easy target for the attacks of his opponents. It has to be realized that, at the time, there were hundreds if not thousands of such descendants and it was well nigh impossible to prove or refute their claims.