# Nasir al-Din al-Tusi

> Persian astronomer (1201–1274)

**Wikidata**: [Q302835](https://www.wikidata.org/wiki/Q302835)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Nasir_al-Din_al-Tusi)  
**Source**: https://4ort.xyz/entity/nasir-al-din-al-tusi

## Summary
Nasir al-Din al-Tusi (1201–1274) was a Persian polymath renowned for his contributions to astronomy, mathematics, philosophy, and Islamic theology. He is most famous for developing the Tusi couple, a mathematical device used in planetary motion models, and for his pivotal role in advancing both the Islamic and scientific traditions of the medieval period.

## Biography
- Born: February 18, 1201, in Tus, Khurasan (modern-day Iran)
- Nationality: Persian
- Education: Studied under notable scholars in Tus, Nishapur, and Baghdad; trained in Islamic jurisprudence, theology, philosophy, and the sciences
- Known for: Founding Maragheh Observatory, developing the Tusi couple, and authoring influential works in astronomy, mathematics, and ethics
- Employer(s): Employed by the Ilkhanid court under Hulagu Khan; associated with the Maragheh Observatory
- Field(s): Astronomy, mathematics, philosophy, Islamic theology, ethics, geography, mineralogy, and optics

## Contributions
Nasir al-Din al-Tusi made significant contributions across multiple disciplines:
- **Astronomical Works**:
  - *Zij-i Ilkhani* (c. 1258): A set of astronomical tables created at the Maragheh Observatory, used for over 700 years in the Islamic world and Europe.
  - *Tajrīd al-Iʿtiqād* (c. 1250s): A treatise on Islamic theology and philosophy, influential in both Shia and Sunni thought.
  - *Akhlaq-i Nasiri* (c. 1250s): A work on ethics that combined Aristotelian and Islamic ethical traditions.
- **Mathematical Innovations**:
  - **Tusi Couple** (c. 1240s): A mathematical model involving a circle rolling inside another circle with twice the diameter, used to explain planetary motion without epicycles.
- **Philosophical and Theological Works**:
  - *Tajrīd al-Iʿtiqād*: A systematic study of Islamic theology that influenced later thinkers like Mulla Sadra.
  - *Akhlaq-i Nasiri*: A foundational text in Islamic ethics, blending Greek and Islamic moral philosophy.
- **Institutional Contributions**:
  - Founded the **Maragheh Observatory** (1259) in Iran, which became a major center for astronomical research and attracted scholars from across the Islamic world.
- **Named After Him**:
  - **K. N. Toosi University of Technology** in Tehran, Iran (established 1928).
  - **Nasireddin**, a lunar crater.

## FAQs
### Who was Nasir al-Din al-Tusi?
Nasir al-Din al-Tusi (1201–1274) was a Persian polymath who made significant contributions to astronomy, mathematics, philosophy, and Islamic theology. He is best known for his astronomical innovations, including the Tusi couple, and for founding the Maragheh Observatory.

### What are the major works of Nasir al-Din al-Tusi?
Some of his most notable works include:
- *Zij-i Ilkhani*, a set of astronomical tables.
- *Tajrīd al-Iʿtiqād*, a treatise on Islamic theology.
- *Akhlaq-i Nasiri*, a work on ethics.
- The **Tusi couple**, a mathematical model for planetary motion.

### What is the Tusi couple?
The Tusi couple is a mathematical device in which a small circle rotates inside a larger circle with twice the diameter. It was developed by al-Tusi to explain planetary motion and eliminate the need for Ptolemy's equant, a concept criticized for violating the principle of uniform circular motion.

### What institutions did Nasir al-Din al-Tusi found or lead?
Al-Tusi founded the **Maragheh Observatory** in 1259, which became a leading center for astronomical research. He also influenced the establishment of **K. N. Toosi University of Technology** in Tehran, named in his honor.

### What was Nasir al-Din al-Tusi's role in the Ilkhanid court?
Al-Tusi served as an advisor to Hulagu Khan, the Ilkhanid ruler, and played a key role in the construction and operation of the Maragheh Observatory under Ilkhanid patronage. His influence extended to both scientific and political spheres.

### How did Nasir al-Din al-Tusi influence Islamic philosophy and theology?
Al-Tusi's *Tajrīd al-Iʿtiqād* is considered one of the most influential works in Islamic theology, summarizing and critiquing earlier philosophical and theological traditions. His synthesis of Avicennan and Illuminationist thought influenced later thinkers like Mulla Sadra.

## Why They Matter
Nasir al-Din al-Tusi profoundly shaped medieval Islamic intellectual traditions and had a lasting impact on global science. His **Tusi couple** became a cornerstone in the development of planetary motion models, later influencing Copernicus and the European Renaissance. His **Maragheh Observatory** was a beacon of scientific inquiry, producing astronomical data used for centuries. In philosophy and theology, his *Tajrīd al-Iʿtiqād* became a standard reference, bridging rationalist and traditionalist schools. His ethical treatise, *Akhlaq-i Nasiri*, also influenced moral philosophy in both the Islamic world and beyond. Without al-Tusi, the progression of both Islamic and global scientific thought would have lacked critical advancements in astronomy, mathematics, and philosophy.

## Notable For
- Founding the **Maragheh Observatory**, a leading medieval astronomical center.
- Developing the **Tusi couple**, a mathematical innovation that influenced Copernicus.
- Authoring *Zij-i Ilkhani*, a highly accurate set of astronomical tables.
- Writing *Tajrīd al-Iʿtiqād*, a landmark work in Islamic theology.
- Composing *Akhlaq-i Nasiri*, a synthesis of Greek and Islamic ethics.
- Serving as a key advisor to Ilkhanid rulers and shaping scientific policy.
- Influencing later polymaths like Avicenna and Qutb al-Din al-Shirazi.
- Being honored through institutions like **K. N. Toosi University of Technology** and the **Nasireddin** lunar crater.

## Body

### Early Life and Education
Nasir al-Din al-Tusi was born on **February 18, 1201**, in **Tus, Khurasan** (modern-day Iran). He was educated under prominent scholars in **Tus**, **Nishapur**, and **Baghdad**, mastering **Islamic jurisprudence**, **theology**, **philosophy**, and the **sciences**. His early training laid the foundation for his later polymathic achievements.

### Career and Institutional Affiliations
Al-Tusi's career spanned multiple roles:
- **Advisor to the Ilkhanids**: He served as a political and scientific advisor to **Hulagu Khan**, aiding in the establishment of the **Ilkhanate**.
- **Maragheh Observatory**: In **1259**, he founded the **Maragheh Observatory** in **Iran**, which became a major center for astronomical research and attracted scholars from across the **Islamic world**.
- **Patronage and Influence**: Supported by the **Ilkhanid court**, al-Tusi used his position to advance scientific and educational initiatives.

### Scientific and Mathematical Contributions
Al-Tusi's scientific legacy includes:
- **Tusi Couple**: A geometric model that resolved issues in Ptolemaic astronomy by replacing the problematic **equant** with a more mathematically sound approach.
- *Zij-i Ilkhani* (c. 1258): A comprehensive set of **astronomical tables** created at the **Maragheh Observatory**, used for over **700 years** in both the **Islamic world** and **Europe**.
- *Tajrīd al-Iʿtiqād* (c. 1250s): A treatise on **Islamic theology** that became a standard reference in **Shia** and **Sunni** thought.
- *Akhlaq-i Nasiri* (c. 1250s): A work on **ethics** that blended **Aristotelian** and **Islamic** moral philosophy.

### Philosophical and Theological Influence
Al-Tusi's philosophical and theological works include:
- *Tajrīd al-Iʿtiqād*: A systematic critique of earlier **Islamic philosophy** and **Ilm al-Kalam**, influencing later thinkers like **Mulla Sadra**.
- *Akhlaq-i Nasiri*: A foundational text in **Islamic ethics**, integrating **Greek** and **Islamic** traditions.

### Legacy and Recognition
Al-Tusi's legacy is commemorated in:
- **K. N. Toosi University of Technology** in **Tehran**, **Iran**, established in **1928** and named in his honor.
- **Nasireddin**, a **lunar crater**.
- His **Tusi couple** influenced **Copernicus** and the **Copernican Revolution**, marking a pivotal role in the history of **astronomy**.

### Connections to Other Scholars and Movements
Al-Tusi was influenced by:
- **Avicenna** (Ibn Sina), whose works on **medicine** and **philosophy** shaped his early education.
- **Qutb al-Din al-Shirazi**, a contemporary and fellow polymath.
- **Fakhr al-Din al-Razi**, a theologian and philosopher whose works he critiqued.
- **Mu'ayyad al-Din al-'Urdi**, an astronomer who collaborated with him at **Maragheh**.

### Affiliation with the Mongol Campaigns
Al-Tusi's life intersected with the **Mongol campaigns**:
- He was instrumental in the **Mongol campaign against the Nizaris** (1253–1256), leading to the fall of the **Nizari Ismaili state**.
- His role in the **Siege of Baghdad** (1258) under **Hulagu Khan** positioned him as a key figure in the **Ilkhanate's** intellectual and political development.

### Publications and Works
Al-Tusi's major works include:
- *Zij-i Ilkhani*: Astronomical tables used for centuries.
- *Tajrīd al-Iʿtiqād*: A treatise on **Islamic theology**.
- *Akhlaq-i Nasiri*: A work on **ethics**.
- *Tusi Couple*: A mathematical model for planetary motion.

### Influence on Later Thinkers
Al-Tusi's influence extended to:
- **Nicolaus Copernicus**, who used the **Tusi couple** in *De revolutionibus*.
- **Islamic philosophers** like **Mulla Sadra**, who built upon his theological and philosophical ideas.
- **Modern Iranian institutions**, such as **K. N. Toosi University of Technology**, named in his honor.

### Personal Life and Death
Al-Tusi died on **June 26, 1274**, in **Baghdad**, after a life dedicated to scholarship and scientific advancement. His works continued to influence both **Islamic** and **Western** intellectual traditions long after his death.

## References

1. A Short History of Astronomy
2. MacTutor History of Mathematics archive
3. Virtual International Authority File
4. BnF authorities
5. al-Aʻlām (Dār al-ʻIlm, 2002)
6. [MacTutor History of Mathematics archive](http://www-history.mcs.st-andrews.ac.uk/Biographies/Al-Tusi_Nasir.html)
7. International Standard Name Identifier
8. CiNii Research
9. Internet Encyclopedia of Philosophy
10. [Biographical Encyclopedia of Astronomers](http://islamsci.mcgill.ca/RASI/BEA/Tusi_BEA.htm)
11. Freebase Data Dumps. 2013
12. Mathematics Genealogy Project
13. Czech National Authority Database
14. LIBRIS. 2012
15. Golden
16. Treccani Philosophy
17. FactGrid
18. HMML Authority File
19. Digital Scriptorium Catalog
20. Catalogo of the National Library of India