This book is a comparative study of two major ShÄ«Ê¿Ä« thinkers ḤamÄ«d al-DÄ«n KirmÄ?nÄ« from the Fatimid Egypt and MullÄ? á¹¢adrÄ? from the Safavid Iran, demonstrating the mutual empowerment of discourses on knowledge formation and religio-political authority in certain IsmaÊ¿ili and Twelver contexts. The book investigates concepts, narratives, and arguments that have contributed to the generation and development of the discourse on the absolute authority of the imam and his representatives. To demonstrate this, key passages from primary texts in Arabic and Persian are translated and closely analyzed to highlight the synthesis of philosophical, Sufi, theological, and scriptural discourses. The book also discusses the discursive influence of Naṣīr al-DÄ«n ṬūsÄ« as a key to the transmission of IsmaÊ¿ili narratives of knowledge and authority to later ShÄ«Ê¿Ä« philosophy and its continuation to modern and contemporary times particularly in the narrative of the guardianship of the jurist in the Islamic Republic of Iran.