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Nasir al-Din al-Tusi

Islamic · Middle East · 1201 to 1274

Persian scholar who wrote a famous book on ethics and works on astronomy, and helped build the centre of learning at Maragha.

What it is

Nasir al-Din al-Tusi (1201 to 1274) was a Persian scholar from the city of Tus, in the northeast of present-day Iran. He wrote on ethics, logic, theology, mathematics and astronomy, and is counted among the outstanding scholars of the thirteenth century in the Islamic world.

He lived through the Mongol conquests and passed from the service of one ruler to another. His work includes both a book on how to live well and a body of exact work on the movements of the stars.

The main ideas

  • A very wide field. His writings run to well over a hundred titles, on astronomy, ethics, logic, mathematics, philosophy and theology among other subjects.
  • Ethics for a patron. His best-known book on ethics, the Nasirean Ethics, was written in the 1230s and dedicated to the Ismaili governor who had taken him in.
  • Theology. He wrote a treatise on Shi'i theology, the Tajrid, which is still highly esteemed.
  • Astronomy as exact work. He compiled tables of planetary movements, the Zij-i Ilkhani, and wrote a treatise on astronomy. He is also remembered for a geometric device, now named after him, that reformed older models of the planets.
  • Learning under new rulers. After the Mongols took the Ismaili stronghold of Alamut, he entered the service of the Mongol ruler Hulegu and ran the religious endowments. He helped build up a centre of learning at Maragha, with an observatory and library.

What it looks like in practice

Imagine a scholar whose city has just fallen to a conquering army, and who is offered a post by the conquerors. They would have to weigh loyalty, safety and the chance to keep learning alive. Al-Tusi faced a choice of this kind, and accounts of how to judge it differ. This is an illustration, not a statement about his motives.

Books and moments

  • The Nasirean Ethics is his famous work on ethics.
  • The Zij-i Ilkhani is a set of astronomical tables, based on research at Maragha.
  • The Tadhkira is his treatise on astronomy, where the Tusi couple is described.
  • A revision of Ptolemy's Almagest shows his work on older astronomy.
  • Maragha is the place where he gathered scholars and where research went on after his death.

Questions and criticism

  • A genuine change of faith? He served for years among the Ismailis and then worked for the Mongols who destroyed their stronghold. His own religious allegiance during those years is described as uncertain. The sources do not settle his motives.
  • Service and survival. He built up a centre of learning under Mongol rule. It is fair to ask what he gave up or accepted to do so.
  • Which dates? The sources differ on the year the Nasirean Ethics was written, so any single year should be read with care.

Close neighbours

The page on Ibn Sina sits closest, since al-Tusi studied his work closely. Ibn Arabi, who lived in the same century, took a more mystical road.

Written by epchē in our own words, and checked against independent sources on 29 October 2026. The sources are listed below.

Who they connect to

Influenced by

  • Ibn Miskawayh · Tusi built his book on ethics on the earlier work of Miskawayh.
  • Ibn Sina (Avicenna) · He defended and explained Ibn Sina's thought against his critics.

Other Islamic thinkers

Sources we used

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