Ibn al-Hayṯam’s Maqāla fī Ḥarakat al-iltifāf

Abstract In Maqāla fī Ḥarakat al-iltifāf , Ibn al-Hayṯam transformed Ptolemy’s mechanism of oscillating epicycles into a solid-sphere model. This innovation led him to reinvent the Eudoxan couple, a device originally developed by Eudoxus in the fourth century BCE and later incorporated by Aristotle into his cosmic system. The treatise became among Ibn al-Hayṯam’s most influential astronomical works. Yet, for modern historians of astronomy, the treatise was believed to be lost until the recent discovery of an incomplete manuscript. This paper presents a critical edition, an English translation, and an analysis of the extant parts of Maqāla fī Ḥarakat al-iltifāf .