Chapter five presents the views of the prominent Muʿtazili scholar Rukn al-Dīn Ibn al-Malāḥimī (d. 536/1141) in his Book of Excellence on the Fundamental Principles of Religion (Kitāb al-Fāʾiq fī uṣūl al-dīn). The Book of Excellence, which is extant in full, is a summary of his larger work, a comprehensive theological summa entitled The Reliable Book on the Fundamental Principles of Religion (al-Muʿtamad fī uṣūl al-dīn), of which only parts survive. The Book of Excellence is an important source for contemporary researchers since it is one of the last available texts from the Sunni Muʿtazili tradition, which disappeared by the end of the classical period in the seventh/thirteenth century. Ibn al-Malāḥimī’s chapter on the imamate, in particular, represents this tradition’s views up until the sixth/twelfth century. It justifies the Muslim community’s right to select its own leaders and affirms the legitimacy of the first four caliphs. Ibn al-Malāḥimī also defends ʿAli’s character against accusations of wrongdoing, while refuting Imami doctrines about his designation (naṣṣ) and infallibility.