Since the ninth century, Shii Muslims have grappled with the question of authority in the absence of a physically present Imam. Today guidance is provided to the Shii community by religious leaders (mujtahids) who rely on rational techniques of deriving new rulings from sacred textual sources. Most scholars date the shift towards rational authority from the late eighteenth century when Vahid Bihbihani’s Usuli (rationalist) school of thought defeated the rival Akhbari (traditionalist) school. Just one generation after Vahid Bihbihani (d. 1791), Usuli scholars excommunicated Shaykh Ahmad Ahsa’i (d. 1825, the founder of the Shaykhi school of thought) from the Shii community for asserting that he derived knowledge directly from the twelfth Imam through intuitive revelation. However, scholars have sidestepped the fact that the founders of the modern rationalist school of thought had made similar claims. Vahid Bihbihani said that a book he had written (entitled Sharh al-mafatih) was given to him in a dream by the twelfth Imam as a scroll. Bihbihani’s most outstanding students, who are considered as the very exponents of Shii orthodoxy, made similar claims. Bahr al-‘Ulum (d. 1797), who was Shaykh Ahmad Ahsa’i’s most influential teacher and a student of Bihbihani, is well-known for his claims to intuitive revelation. Why then was Shaykh Ahmad cast out of the orthodox community? Based on unpublished manuscripts of Bihbihani’s work, nineteenth century Shii biographical dictionaries, and the work of scholars such as Bahr al-‘Ulum and Shaykh Ahmad Ahsa’i, my paper will argue that, although the founders of modern rational thought claimed to have supernatural access to the twelfth Imam, such claims to authority were on their way out as the nineteenth century began. Usulis elevated knowledge derived by rational means over knowledge derived from intuitive revelation. Conversely, Shaykh Ahmad Ahsa’i preferred intuitive revelation over rational knowledge. Although intuitive knowledge had been essential to Shiism from its inception, nineteenth century Usuli scholars could not allow it to trump the rationalism that they had built their school of thought around. Furthermore, Vahid Bihbihani had introduced the tool of excommunication (takfir) as a means to deal with unorthodox claims to authority. Bihbihani had used this tool against Akhbaris and his students continued the practice against both Shaykhis and Sufis. In broad terms, this paper will provide a better understanding of the development of modern Shii orthodoxy and will explain how the Shii definition of charismatic authority has changed over time.