The exclusivism of monotheism leaves no space theologically for polytheists and little even for other types of monotheist. Historical realities and the inter-connectedness of the sacred history of the three monotheisms has tended to permit followers of different monotheist faiths greater latitude than heretics within. The Pact of Umar provided a model for the continued existence of certain minorities under Islam. But the logic of monotheism has tended also to dictate religious uniformity as an ultimate aim. Large-scale conversion to Islam and the corresponding decline in Jewish and Christian numbers led to growing popular as well as some intellectual hostility to the continued existence of Jewish and Christian minorities in the medieval Islamic world. But the Almohads stand out for their attempt actively to rid their territories of both the other monotheistic faiths. Here the intellectual genealogy of their attitude is explored in the light of a passage in Ibn Ḥazm that explicitly denies the right of Jews and Christians to retain their faiths under the rule of Islam.