Nasir al-Din al-Tusi, the 13th-century Shi'i philosopher and scholar, is one of the most controversial Muslim personalities of his time. His contributions to different fields of learning, including astronomy, theology and philosophy, won for him the honorific titles of scholar ("Muhaqiq") and the "Eleventh Intellect". In Isma'ili circles he was held in the highest esteem and addressed as "Da'i al-du'at wa khwaja-i ka'inat", chief propagandist and...