One of the most enduring sources of conflict among Muslims is the question of who or what represents legitimate power and authority after the Prophet Muhammad. This introduction briefly examines the diverse answers that key representatives of the classical Islamic tradition offered to this controversial question. A concise overview of early Islamic political history is followed by a survey of Islamic thought on the subject of authority in the formative (seventh-ninth centuries) and classical periods (ninth-thirteenth centuries). This introduction presents the views of six major theological schools of the classical period: Ashʿarism (representative of Sunnism), Muʿtazilism, Ibadism, Twelver Shiʿism, Ismaʿilism, and Zaydism. Finally, this chapter discusses the classical Arabic texts that appear in English translation in this anthology as well as their respective themes, authors, and historical contexts.

Chapter four presents the views of the prominent Twelver Shiʿi scholar Muḥammad b. al-Ḥasan al-Ṭūsī (d. 460/1067). Like other Zaydis and Twelver Shiʿis of his era, al-Ṭūsī incorporated Muʿtazili doctrines into his writings on theology. His seminal work on the imamate is an abridgment of The Curative Book (al-Shāfī) by al-Sharīf al-Murtaḍā (d. 436/1044). Al-Ṭūsī’s work was similarly entitled The Curative Book on the Imamate: A Paraphrastic Rendering (Talkhīṣ al-Shāfī fī al-imāma) and reflected his own understanding of the text. Both al-Murtaḍā and al-Ṭūsī ground the Twelver conception of the imamate in Bahshamī Muʿtazili theology to argue for the rational necessity of the imamate and its necessity according to the Qurʾan and hadith. They accomplish the former by tying the existence of imams to the existence of moral obligations (taklīf) in the sight of God. As long as moral obligations exist, humans need imams who function as a type of divine assistance (luṭf).