The sacred law of Islam, the Sharī‘a, occupies a central place in Muslim society, and its history runs parallel with the history of Islamic civilization. It has often been said that Islamic law represents the core and kernel of Islam itself and, certainly, religious law is incomparably more important in the religion of Islam than theology. As recently as 1959, the then rector of al-Azhar University, Shaykh Mahmūd Shaltūt, published a book entitled ‘Islam, a faith and a law’ (al-Islām, ‘aqīda wa-sharī‘a), and by far the greater part of its pages is devoted to an exposé of the religious law of Islam, down to some technicalities, whereas the statement of the Islamic faith occupies less than one-tenth of the whole. It seems that in the eyes of this high Islamic dignitary the essential bond that unites the Muslims is not so much a common simple creed as a common way of life, a common ideal of society. The development of all religious sciences, and therefore of a considerable part of intellectual life in Islam, takes its rhythm from the development of religious law. Even in modern times, the main intellectual effort of the Muslims as Muslims is aimed not at proving the truth of Islamic dogma but at justifying the validity of Islamic law as they understand it. It will therefore be indicated for us to survey the development of Islamic law within the framework of Islamic society and civilization, tentative as this survey is bound to be. Islamic law itself is one of our most important sources for the investigation of Islamic society, and explaining Islamic law in terms of Islamic society risks using a circular argument.