Nasir al-Din al-Tusi

Nasir al-Din al-Tusi (born in Tus, north-eastern Iran, 597/1201; died near Baghdad 672/1274) was one of the most influential scholars of the medieval Islamic world, working across theology, philosophy, mathematics and astronomy. Sources agree he came from a Twelver Shi'i family — Imami Islam being the branch that recognises a line of twelve Imams — and studied at Tus, then at the great learning centre of Nishapur, where he read the philosophy of Avicenna (Ibn Sina). As a young man he entered the service of the Nizari Ismailis (a separate Shi'i community) in the Quhistan region and later at their mountain fortress of Alamut, where he produced major works including the ethical treatise Akhlaq-i Nasiri. When the Mongol leader Hulagu took Alamut in 1256, al-Tusi joined his entourage; reports place him in the Mongol camp at the fall of Baghdad in 1258, though his exact role is described differently by different sources. With Mongol backing he founded and directed the observatory at Maragha, among the most advanced of its age. His Tajrid al-i'tiqad became a cornerstone of philosophical Imami theology, drawing centuries of commentary. Whether his Ismaili period reflected genuine conviction or political necessity was debated even in his own time; the sources do not settle it. He died of illness on a journey to Baghdad and, by his own request, was buried at the Kazimayn shrine.