Abstract: The present study seeks to explore a neglected but important development in the history of Iranian Shiʿism in the period immediately preceding the beginning of full-scale Western economic and political penetration. Shiʿism has, in general, not witnessed the emergence of significant reformers in the modern period, comparable to those of the Sunnī world. Earlier, much attention was focused on Babism and Baha’ism, but these movements are less reformist than heterodox in nature and, in the end, seek to move beyond an Islamic frame of reference altogether. This, however, is paradoxical, in that early Babism and the Shaykhī school from which it emerged both laid considerable stress on orthodoxy and on rigid Islamic practice. It is the purpose of this thesis to demonstrate the place of this paradox within the wider context of Twelver Shiʿism as a whole and to explore the role of authority claims and the interplay of charismatic and legal authority as basic factors in the emergence of the Shaykhi and Bābī movements.