TUsI’s production also embraced all the mathematical sciences of antiquity: arithmetic, geometry, astronomy, astrology, and optics.
His innovation concern the rewriting of some Arabic masterpieces. TiusI rewrote them on the basis of the most ancient translations, choosing the terms best suited to rendering the meaning more comprehensible. He avoided repetitions of some concepts, elaborated them using contemporary terms, and explained them. These recensions became hybrids and were identified with the name of taharlr. TiisI dealt with all the translated texts that were available to him and revised the Arabic translations of Euclid, Aristarchus, Theodosius, Apollonius, Archimedes, Menelaus, Ptolemy, and many others.
TtisI’s main contribution to the mathematical sciences was in trigonometry. In his Shakl al-qita‘, on the basis of the works of Abu l-Wafa’, Mansur ibn ‘Iraq and al-BIrtini, TUsI developed trigonometry without using Menelaus’ theorem or astronomy. For the first time he gave the field of trigonometry an independent identity, deciding to devote a special treatise to the innovations that he had met in his various recensions and offering a complete picture of the subject.
In his Jawami‘ al-hiisab, completed in 1246, he described the arithmetical operations in a simple way accessible to a wide audience, combining the Greek method with the Indian one. He introduced a new method for the extraction of roots, a method that had been used by Chinese mathematicians, but was new to him. A part of Jawami‘ al-liisab is devoted to what he called ‘‘the arithmetic of the astrologers.” In the section, he explained that arithmetical operations could be used on sexagesimal entities such as signs, degrees, minutes, and seconds.
In the field of geometry, Tiisi followed al-Khayyam and in his al-Risala al-shafi‘iyya he examined Euclid’s fifth postulation, proving that the theory was a failure.
Tusi’s astronomic production encompassed all forms of knowledge of his day. When he dealt with the recension of the Almagest in 1247, Tiusi denounced the Ptolemaic theory of latitudinal movement of the planets and introduced a form of mathematical theorem, known as the ‘‘Tusi couple.’’ The ‘‘couple’’ produces a linear movement as a result of the two circular movements.
In about 1260, he wrote the famous Tadhkira, in which he improved the research he had previously done. In a chapter in the text he proved the theorem of the ‘‘couple’’ and for the first time a solution was expounded for the movement of the planets. This theory could be extended beyond the latitudinal theory of planets preserving uniform circular motion, and it became the fundamental heritage for later astronomers in the Islamic world.
Htilagu’s generosity and interest allowed TusI to devote himself for 30 years to the study of astronomy and to build the famous observatory at Maragha. The most important and best-known work that was produced by the leading lights at the observatory was Ztj-i tlkhant, originally written in Persian and then translated into Arabic and other languages. Parts of the text were also translated into Byzantine Greek during the thirteenth and fourteenth centuries.
In the field of mineralogy, Tiisl wrote the Tanksukh-nama in Persian, based on Islamic sources such as the works of Jabir ibn Hayyan, al-Kindl, Multammad ibn Zakariyya’ al-RazI, ‘Utiirid ibn Multammad, and al-Birtinl. The text deals with the four elements and their combinations and a fifth quality is introduced, called temperament or turn of mind, which can accept the forms of the different species. The text also deals with the theories of vapors, sunrays, colors, precious stones, metals, and perfumes.
TusI also wrote some works on medicine, along the lines laid down by Avicenna. Among other works, he wrote the Qawantn al-tibb and a commentary on Avicenna’s Canon. TUsl’s medical point of view was mainly philosophical and his main contribution concerned psychosomatic medicine, which he discusses in his ethical writings, above all in Akhlaq-i nasTrt.
Ttisl’s scientific and philosophical contribution was formidable and innovative. to him, Maragha became the principal center of production of the ‘‘new astronomy.’’ Unfortunately, many texts by Tiusl have not yet been edited and therefore are not accessible to contemporary scholarship.
See also: > Abut l-Barakat al-BagdadI > Aristotle, Arabic
> Astronomy and Astrology in the Arab World > Being
> Ethics, Arabic > Fakhr al-Din al-RazI > al-FarabI, Abu Nasr > Happiness > Ibn SIna, Abui ‘AlI (Avicenna)
> Isma‘Ili Philosophical Tradition > Kalam > Logic in the Arab and Islamic World > Mathematics and Philosophy in the Arab World > Medicine in the Arab World
> Metaphysics > Miskawayh, Abui ‘AlI > Natural
Philosophy, Arabic > Philosophical Psychology > Philosophy, Arabic > Political Philosophy, Arabic > al-SuhrawardI, Shihab al-DIn Yaltya al-Maqtuil
World History
