al-Risāla al-Muʿīniyya and its Supplement

This book is the first critical edition of two important Persian treatises by Naṣīr al-Dīn al-Ṭūsī, al-Risāla al-Muʿīnyya (The Muʿīniyya treatise) and its supplement, Ḥall-i Mushkilāt-i Muʿīniyya (Resolution of the difficulties of the Muʿīniyya treatise), both written by Ṭūsī during his long residence in the Ismāʿīlī fortresses of Quhistān. Whatever the reason, after the rise of the Ilkhans and the fall of the Abbasid caliphate, Ṭūsī decided to remove the Ismāʿīlī remnants from some of his works, including al-Risāla al-Muʿīniyya, and Ḥall-i mushkilāt-i Muʿīniyya, so that no Ismāʿīlī references remained in either text. He even changed the title of the book from "al-Risāla al-Muʿīniyya" to "al-Risāla al-Mughniya" (The sufficing treatise). The copy of the Muʿīnyya and Ḥall that includes Ṭūsī's revisions became the base copy for the current edition.

The Ḥall contains Ṭūsī’s first publication of his device (now known as the Ṭūsī-couple) and its application to his planetary models.