This book is an English translation of the award-winning book by Mohammad Ali Amir-Moezzi on the Book of the Proof (Kitab al-Hujja) part of the Sufficient Book (Kitab al-Kafi), authored by one of the most celebrated religious authorities and a foundational figure of Shi'i Islam, Muhammad ibn Ya'qub al-Kulayni (d. ca. 940 CE). The significance of this source for the formation and development of Shi'i beliefs and doctrines...