Naṣīr al-Dīn al-Ṭūsī’s al-Tadhkira fī ʿilm al-hayʾa profoundly shaped the tradition of astronomy in the Islamicate world during the post-Avicennian era. However, Ṭūsī himself emphasized that al-Tadhkira was not exhaustive in its mathematical elaborations and urged scholars to refer Ptolemy's Almagest with it. Despite its significance, Ṭūsī’s redaction of the Almagest (Taḥrīr al-majisṭī) remains underexplored.
This presentation investigates Ṭūsī’s Taḥrīr, a critical text that consists of an Arabic translation of the Almagest with Ṭūsī’s own commentaries. While over 100 manuscripts of Taḥrīr survive—which indicates it was widely read in the Islamicate world—the work has neither been translated into English nor edited. Previous studies have predominantly focused on Book XIII, Chapter 2, known for introducing the “prototype of the Ṭūsī Couple.” However, Ṭūsī’s broader commentaries reveal significant insights into post-12th-century astronomical advancements.
For instance, Ṭūsī commented detailed trigonometric annotations, absent from al-Tadhkira, on Ptolemy’s concept of chords. Following this commentary, the Taḥrīr employs trigonometry instead of chords. Furthermore, he utilized alternative forms of Menelaus’s theorem, ʿal-shakl al-mughnī’ and ʿal-shakl al-ẓillī’, in his comments, which enabled the development of new theories across various areas of his commentary. These contributions highlight Taḥrīr as a foundational source for later astronomical methodologies.
Notably, scholars like al-Samarqandī, al-Nīsābūrī, and al-Birjandī extended this tradition through their commentaries, demonstrating the enduring impact of Taḥrīr. Thus the Taḥrīr tradition needs to be considered with al-Tadhkira to fully appreciate the cosmological developments of the post-Avicennian era.

This paper discusses Molla Ahaveyn’s (d. 904/1499) work titled Issues in Theoretical Astronomy (al-Ishkālāt fī ʿilm al-hayʾa). Molla Ahaveyn was an Ottoman scholar who flourished in the fifteenth century, and his work addresses various problematic issues inherent in Ptolemaic astronomy. Critical engagement with Ptolemaic astronomy emerged at an early stage in Islamic intellectual history, notably with Ibn al-Haytham’s (d. around 432/1040) Doubts Concerning Ptolemy, which became a seminal and influential text. Subsequently, challenges to the Ptolemaic system were elaborated in both independent treatises and comprehensive works containing dedicated chapters on this topic. Molla Ahaveyn, an Ottoman scholar active in Istanbul, also contributed to this intellectual tradition by critically engaging with the Ptolemaic system. This paper aims to examine his approach to Ptolemaic astronomy and contextualize his work within the broader discussions on reforming the Ptolemaic system. Furthermore, this study highlights the significance of Molla Ahaveyn’s contribution as part of the broader fifteenth-century Ottoman discourse on astronomy.