The period in which formative developments took place in Islam, and at the end of which Muslim orthodoxy crystallized and emerged, roughly covered a period of two centuries and a half. Sufism has exercised, next to orthodoxy, the greatest influence on the Muslim community because of its insistence on the inner reform of the individual, and has, ever since its birth, posed the biggest challenge to orthodoxy down to the dawn of modern times. From the sixth/twelfth century onwards, Sufism became a mass movement in the form of organized brotherhoods which invaded the entire Muslim world from east to west. The criticism of historic Muslim social institutions by orientalists and Christian missionaries specifies the objectives of social reform for the Modernist. A real, effective renaissance of Islam is not possible until educational developments reach the point of contributing from an Islamic standpoint to the humanities of the world at large.