Nineteenth-century Islam witnessed the emergence of several messianic movements... It was only in Shi'i Iran that a movement appeared which broke entirely from Islam

Beginning in 1844 as a reactionary messianic movement within Shi'ism, Babism had, by 1848, attempted the abrogation of the Islamic legal system and, within another year, proclaimed the replacement of Islam by a new divine revelation. This extraordinary development, which was cut short by the physical repression of the Babis by 1852, was based on a series of claims to original charismatic authority by the founder of the movement, Sayyid 'Ali Muhammad Shirazi, the Bab. Although he finally claimed to be a divine ‘manifestation’ sent by God with a new book and law, Shirazi had commenced his mission by urging no greater claim than that of representative or ‘gate’ (bab) of the Imam –– something not very far removed from what was later asserted of the supreme marja' or what is today claimed for Khumaini by many of his followers. Baha'ism, which emerged out of Babism in the 1860's, was based on a similar claim to divine authority superseding that of the past, and achieved an even further-reaching charismatic breakthrough. In the end, the Baha'is claimed for their movement the status of a new religion, independent of Islam, a claim which has been furthered to some extent by the relative success of their missionary enterprises outside Iran throughout this century.

Apart from their undoubted intrinsic interest, Babism and Baha'ism seem to me to be significant in the present context for a number of reasons. It is, first of all, worth noting that, although nineteenth-century Islam witnessed the emergence of several messianic movements, such as the Mahdiyya of the Sudan or the Ahmadiyya in India, all of these remained within the bounds of Islam, from their own point of view, at least. It was only in Shi'i Iran that a movement appeared which broke entirely from Islam and, in the end, successfully established itself as a new and, in some areas, even a rival religion.

(ISLAM IN THE MODERN WORLD, Edited by DENIS MACEOIN AND AHMED AL-SHAHI, ROUTLEDGE LIBRARY EDITIONS: POLITICS OF ISLAM)