Al-Ṭūsī's Recension Method in Comparison to the Maghribī's Recension of Theodosiu's Sphaerica

This article examines al-Ṭūsī’s and Maghribī’s recensions of Theodosius’ Sphaerica by comparing their features and differences. Al-Ṭūsī adheresto the original text of Sphaerica، however، by adding some postulates and three lemmas، he enriches the mathematical structure of the treatise. Al-Ṭūsī’s composition style reveals that he intended to prepare a pedagogical textbook، his statements are concise and precise and he presents demonstrations for all the theorems. Several manuscripts of al-Ṭūsī’s recension are extant، one of which has been transcribed before his death. The only other extant recension of Sphaerica belongs to Muḥyeddīn Maghribī. Maghribī changes the style of the original text by merging some theorems، changing the demonstrations and modifying the diagrams. Although he inserts some additional lemmas into the text، he leaves some simple proofs incomplete. One of the extant manuscripts of Maghribī’s recension has been transcribed prior to his death. In sum، we can say that Ṭūsī’s recension enriches the mathematical content of the treatise، whereas Maghribī’s recension includes some superfluous and superficial changes and lacks the mathematical force of Ṭūsī’s recension.