al-Tusi, Nasir al-Din

(597–672/1201–74)

   It is often claimed that philosophy effectively came to an end in the Islamic world with the death of Ibn Rushd at the close of the twelfth century. This is certainly an exaggeration, in part because of the various non-Peripatetic movements that continued to flourish well beyond that time (the Isma‘ilis, the school of Illumination, philosophical Sufism, the philosophical theology of the ‘modern’ Ash‘arites and the Twelver Shi‘ites). But it is also false because of thinkers like the Persian scientist-philosopher al-Tusi (also known as Khwaja Nasir), who was arguably the towering intellectual figure of the thirteenth century, as well as the great defender and reviver of Peripatetic thought in the East. Brought up as a Twelver Shi‘ite, al-Tusi benefited from an unusually broad, ambitious and non-sectarian education. He studied the rational or ‘ancient’ sciences (logic, philosophy, mathematics, natural science) as well as the traditional Islamic sciences and had the opportunity to familiarize himself with Isma‘ili doctrines (his later writings show a knowledge of, and respect for, Sufism and Illumination as well). In his early thirties, he joined the Isma‘ilis, and even lived for twenty years in their storied mountain fortress of Alamut. However, when the Mongol invasion of Iran smashed the Isma‘ili da‘wa, al-Tusi converted back to Twelver Shi‘ism and even became advisor to the Mongol conqueror Khan Hülegü, who prized his astronomical expertise quite highly. Hülegü brought al- Tusi along during his conquest of Baghdad (which brought about the end of the ‘Abbasid caliphate), put him in charge of religious endowments and affairs, and placed considerable scholarly and scientific resources at his disposal, most notably the famous astronomical observatory at Maraghah, which the Khan had built for the philosopher. There is some disagreement about the depth of al-Tusi’s commitment to Isma‘ilism; it may have been a function of political expediency, much as some of his subsequent choices were. Yet during that period, he used the extensive library at Alamut to produce many of his most important theological, philosophical and scientific works, and scholars have detected residual Isma‘ili doctrines in his later, ostensibly post-Isma‘ili works (e.g. the imam’s authoritative teaching [ta‘lim] and the unchangeability of God’s will concerning the designation [nass] of the imam). Al-Tusi’s chief presentation of Isma‘ili doctrines can be found in the Paradise of Submission (Rawda-yi taslim); another key work is his autobiographical Contemplation and Action (Sayr wa suluk). His most important contribution to Twelver thought is the enormously influential Abstract of Belief (Tajrid al-i‘tiqad), which revitalized Imami theology by introducing rigorous new metaphysical terminology and arguments. His most essential work of Peripatetic philosophy is the Commentary on the Directives and Remarks (Shahr al-Isharat wa al-tanbihat, also known as the Hall mushkilat al-Isharat), a devastating response to an earlier, critical commentary on Ibn Sina’s Isharat by the Ash‘arite theologian Fakhr al-Din al- Razi. It is considered the decisive statement of Ibn Sina’s thought and has deeply influenced the way he is read in the tradition. Later, after al-Tusi repudiated his Isma‘ili affiliations, he responded in a similar vein to al-Shahrastani, who had written an Isma‘ili-tinged critique of Ibn Sina entitled Wrestling with the Philosophers (Musara‘at alfalasifa). Al-Tusi’s polemical rejoinder, cleverly titled The Floorings of the Wrestler (Masari‘ al-musari‘), might be seen as a more successful historical counterpart to Ibn Rushd’s Incoherence of the Incoherence (which, compared to its own target – al-Ghazali’s Incoherence of the Philosophers – was virtually ignored in the Islamic world). Al-Tusi also produced several ethical works, the most important being The Nasirean Ethics (Akhlaq-i Nasiri), which builds upon the ethical thought of Miskawayh, the economic insights of Ibn Sina (as well as the Neopythagorean Bryson’s Oikonomikos) and the political philosophy of al-Farabi. It is one of the most highly regarded works of Islamic moral philosophy written in Persian. Among his numerous logical works, the Foundations of Inference (Asas al-iqtibas) is the most important; it is considered second only to the comparable section in Ibn Sina’s Healing. Finally, al-Tusi produced numerous mathematical and scientific works that made significant original contributions to arithmetic, geometry, trigonometry and astronomy. The most well-known of these is the Ilkhani Tables (Zij-i ilkhani), the result of his fruitful research at the Maraghah observatory – and more generally of the institutionalization of the rational sciences, which until then had been almost entirely dependent upon private patronage or individual initiative.

   See Aristotle; Ibn Sina; Isma‘ilis; Neoplatonism; al-Razi, Fakhr al-Din; science; al-Shahrastani; Twelver Shi‘ites

   Further reading: Daftary 1990; Nasr 1996; Nasr with Aminrazavi 1999; al-Tusi 1964, 1992, 1997