cosmologies, was not concerned only with the origin of the universe but also with the purpose of the universe and with the role of humans within this purpose. Humans constitute a microcosm of the greater cosmos, and serve as a link between the spiritual and material realms of existence. Cosmology, with its metaphysical and religious overtones joined to more physical ideas, served as one of the most important links between the concept of nature and the central concerns of Islam.
Astronomy was one of the most important of the Islamic sciences, relating genuine observations of nature with mathematical calculations and models yet also making contact with the more speculative cosmological ideas. Knowledge of the night sky had a long history in Arab culture, was explicitly referred to in the Quran, and was the subject of the earliest translations of Greek and Persian texts. Ptolemy’s Almagest was quickly incorporated into Islamic astronomy, and its observational data continuously improved. The Muslim astronomers were excellent at measurement and observation, establishing major observatories at Isfahan, Maragha, and Samarkand plus a large number of smaller installations (Rayy, Shiraz, Baghdad, Rakka, Cairo, Ghazna, etc.). These observatories were outfitted with improved instruments of various sorts, such as large measuring arcs, sophisticated versions of the sundial, astrolabes, quadrants, and celestial globes. The astrolabe, in particular, was perfected to a high degree. Increasingly precise measurements were compiled into extensive astronomical tables (known as zij) and were used for both practical and theoretical purposes. Practical uses included improvements of the calendar, timekeeping, and establishing the direction toward Mecca (all needed for purposes of Islamic ritual and prayer). Theoretical issues involved the improvement of Ptolemy’s complex model of the planetary movements, which employed epicycles, deferents, and equants. Better data induced Muslim astronomers to look critically at the assumptions and methods of the Ptolemaic system, resulting in a literature that extended over several centuries. A particularly pressing question involved the lack of uniform circular motion resulting from the use of equants. This problem was solved by Nasir al-Din al-Tusi, who developed a mathematical construction that preserved uniform circular motion, now popularly referred to as the Tusi Couple (there is evidence that Copernicus was influenced by Ibn al-Shatir’s use of the Tusi Couple in astronomy). The zij tables were also useful in astrology, further connecting the order in the night sky to order at all levels of the cosmos. Islam produced many thinkers who made important contributions to astronomy, among the most noted being al-Biruni, Ibn Qurra, al-Battani, al-Khwarizmi, al-Tusi, al-Haytham, al-Shirazi, al-Urdi, Ibn Bitruji, al-Juzjani, and al-Shatir. The relationships between astronomy and mathematical work, Aristotelian physical thinking, and the metaphysical conception of order in the cosmos made astronomy a central element in the concept of nature in Islamic thought.
Mathematics itself was one of the most sophisticated parts of the Islamic intellectual tradition. Ideas of logical structure and geometry were inherited from the Greeks, advanced computational methods from the Babylonians, and advanced number theories came from India. The idea of zero, and its use as a place-holder in a decimal number system, was adapted from Hindu thought, improved upon, and ultimately transmitted to European culture as the famous “Arabic numerals” that we still use today. Important advances in working out the use of this number system to make computations simply and efficiently (i.e. arithmetic) were pioneered by Muhammad al-Khwarizmi, one of the greatest mathematicians in history. Al-Khwarizmi is also famous for another major achievement, namely the development (in some ways, the invention) of algebra. Both “algebra” and “algorithm” are words based on terms coined by al-Khwarizmi. Islamic mathematicians like al-Haytham, al-Tusi, and Omar Khayyam also made important advances in geometry and trigonometry. “It was only much later, in the nineteenth century, that the medieval Muslims were understood to have defined what came to be called Euclidean geometry, and that, without realizing it, they had pointed the way toward the discovery of independent non-Euclidean disciplines.”30 Algebra continued to advance, with a variety of solutions found for second and third degree equations, and Khayyam also systematized these advances. The mathematics of conic sections, inherited from Alexandrian Greek culture, was also studied and advanced by Muslim mathematicians. Mathematics, along with its intrinsic importance, played roles that were both physical and metaphysical in Islamic culture. Mathematics was applied to understanding musical acoustics and optics, as well as astronomy. But in addition, the Neoplatonic and Pythagorean understanding of mathematics as the mystical substratum of reality was also deeply embedded in Islamic culture and related to the cosmic order revealed in the Quran.
In the study of music, especially, the physical and metaphysical aspects of mathematics blend together. Muslim studies of music continued along the lines begun by the Pythagoreans, relating musical intervals to mathematical integer ratios. Studies of this sort were written by al-Kindi, al-Farabi, and the Ikhwan al-Safa (Breathren of Purity), unifying musical intervals with cosmological and astronomical ideas by means of mathematical ratios. Meanwhile, another area in which mathematics played a prominent role was the study of light, optics. The study of optics was arguably one of the premier Muslim contributions to science. Al-Kindi studied the reflection of light and visual perception, while al-Razi and Ibn Sina wrote on optics from an Aristotelian perspective. The towering figure of Islamic optical investigations, however, is Ibn al-Haytham (Latinized as Alhazen). Al-Haytham performed experimental studies and mathematical analyses of refraction and reflection of light, formation of rainbows, parabolic mirrors, and visual perception. His theory of visual perception was close the modern idea, involving image formation by the eye of light emanating from the perceived object. Al-Haytham’s work in the areas of rainbow formation and the camera obscura were later continued by al-Farisi, who considerably improved the explanation of rainbows (which had also interested the Ikhwan al-Safa). The work of al-Haytham also influenced the thinking of European figures such as da Vinci and Roger Bacon.
Medicine was another discipline for which many treatises were translated almost from the time of the Prophet. Gondeshapur, in Persia, was already an important center of medical information and practice when the Arabs conquered it in 638. The Greek medical heritage of Hippocrates, Galen, and Dioscorides became available, along with knowledge of Indian medicine and the practical skills of the Nestorian community. In addition, the wealthy and well-organized Caliphate established large hospitals where medical expertise was concentrated, improved, and transmitted to students. Many prominent faylasufs were actually primarily physicians. Two of the prominent early examples of this category are Ibn Sina and al-Razi (Latinized as Rhazes). They both wrote encyclopedic medical reference texts, and Al-Razi is also noted for his work on smallpox. Muslim physicians continued to improve on the legacy they had inherited from Greek and Hindu sources, investigating human anatomy, contagious diseases, and pharmacology, eventually establishing a literature critical of the old sources and writing new medical texts based on their own discoveries. Among the more prominent figures in this movement were Ibn Rushd, Ibn al-Nafis, Ibn al-Khatib, al-Zahrawi, and Ibn Zuhr; among their accomplishments were studies of blood circulation, the anatomy of the eye, the idea of contagion, and the development of advanced surgical techniques and instruments. Also worthy of note is the vast pharmacological compendium written by Ibn al-Baytar, with more than a thousand medicinal plants included. In addition to the simple herbal remedies, Muslim pharmacology also began to include prepared drugs based on alchemical processes.
Alchemy was an important, if sometimes esoteric, part of the Islamic intellectual tradition, and the application of alchemy to pharmacology was only a small part of the entire field. The Muslims inherited the strong tradition of Alexandrian alchemy from Hellenic culture and later added to this the alchemical ideas if India and China. The ancient sources of alchemy in craft traditions, metal smelting, and shamanic practices had already been transformed by contact with both philosophical and mystical currents by the time it entered Islam. All these aspects of alchemy, both practical and esoteric, were retained and amplified within Islamic culture, and new elements of experimentation and quantitative thinking were added. The most important early figure by far in Islamic alchemy was Jabir ibn Hayyan (Latinized as Geber), who lived in 8th century Baghdad and to whom many treatises are attributed. The central idea of Jabir’s work is “balance,” a concept that seems to refer simultaneously to numerical amounts of differing elemental principles of substances and to spiritual and physical attributes of these substances. Some of the later alchemical investigators, such as al-Biruni, al-Khazini, and
