Imam Muhammad al-Baqir was one of the most erudite Muslims of his age, and played a significant role in the history of early Islam. At once a versatile leader and scholar in the eighth-century Muslim world, he was also an authority on the exegesis of the Qur'an, the traditions of the Prophet, and all matters relating to the rites, rituals and practice of Islam. Using hitherto largely ignored Shi'i sources, both published and unpublished, Arzina Lalani explores al-Baqir's pivotal contributions to Islamic thought in its early formative period, contributions that were powerfully to affect developments in Shi'a law, theology and religious practice. Dr. Lalani's work presents the first systematic account of the life, career and teachings of this brilliant eighth-century luminary.