Recent events in Egypt and Algeria, as well as the continuing difficulties of Christians in Iran and the Sudan, have returned the topic of Islamic militancy to Western newspapers. Concern for the situation of world Christianity requires of Catholics some grasp, however non-specialist, of where such militancy comes from and whither it is going. The 1994 Roman Synod of the Catholic churches of Africa was much exercised by the problem, though to judge from the reported speeches of the bishops, few had more to recommend than ‘dialogue'—that contemporary Vaticanesque panacea. To understand why the revolutionary Islam characteristic of a major segment of the Muslim world in the late twentieth century aims at nothing less than the comprehensive take-over of the civil societies where Islam is present, one sine qua non is an acquaintance, at least in broad outline, with the origins and development of the Islamic faith as a whole.