Abu 'Ali al-Husayn ibn Abdallah ibn Sina

980-1037

Ibn Sina, known in the West as Avicenna, was the medieval Islamic world's most important philosopher-scientist. His unique codification of traditional learning into an Aristotelian framework exerted a strong influence on scholasticism in the West. His al-Qanun fi al-Tibb (Canon of medicine) remained the standard medical text until the seventeenth century, while his Kitab al-Shifa (Book of healing) synthesized logic, physics, mathematics, and metaphysics.

Ibn Sina was born in 980 in Afshana, near Bukhara in central Asia (now Uzbekistan). A child prodigy, he was able to recite the Koran by age 10, and by 16 had sufficiently mastered contemporary medical knowledge so that he was able to practice medicine. He was later a jurist at Korkanj, an administrator at Rayy, and both physician and vizier to the Prince Shams al-Dawlah of Hamadan (1015-22). After Shams al-Dawlah died, Ibn Sina was imprisoned. He was released when Ala al-Dawla of Isfahan temporarily occupied the city. Ibn Sina spent his remaining years as Ala al-Dawla's physician. He died of a mysterious illness in 1037 at Hamadan while on campaign with his patron.

Ibn Sina began al-Qanun fi'l-Tibb while at Rayy. Its five books provide a systematic overview and synthesis of all medical knowledge, as supplemented by Ibn Sina's own research and ideas on scientific methodology. He formulated the rules of agreement, difference, and concomitant variation as well as rules for isolating causes and analyzing quantitative effects. The quality and completeness of the Qanun was such that it superseded all other Muslim medical treatises. Translated by Gerard of Cremona (1114-1187) during the twelfth century, the Qanun acquired almost undisputed authority during the Middle Ages.

Ibn Sina's Kitab al-Shifa (1021-23) was a composite work of philosophy and science. In this volume he synthesized Aristotelian and Neoplatonic thought with Muslim theology. The Kitab also contains many original scientific ideas. He proposed a corpuscular theory of light, which implied a finite speed for light. He distinguished between different forms of heat and mechanical energy and contributed to the development of the concepts of force, infinity, and the vacuum. He also investigated the relationship between time and motion, concluding they must be interrelated since time can have no meaning in a world devoid of motion.

Kitib al-ma'adin, appended to a medieval translation of Aristotle's Meteorologica, appears to be an alternate version of parts of the Kitab. It contains Ibn Sina's views on the formation of stones and mountains and is the main source for medieval mineralogy and geology.

Based on his observation that certain springs could petrify objects, he postulated the existence of a mineralizing or petrifying virtue within the Earth. He believed mountains were formed through sedimentation and accretion of petrified clays as the seas retreated from land, and valleys were created by the erosive action of water. He also hinted at a cyclical process of mountain formation and decay. Ibn Sina's division of minerals into salts, sulfurs, metals, and stones was retained until the end of the eighteenth century.

Ibn Sina was well versed in alchemy. He subscribed to Jabir ibn Hayyan's (721?-815?) theory that all substances were derived from sulfur (idealized principle of combustibility) and mercury (idealized principle of metallic properties). However, he actively sought to separate medicine from alchemy's less tenable claims; and contrary to his contemporaries, he did not believe it possible to transmute one substance into another.

In the realm of astronomy, Ibn Sina made observations, invented a device similar to a vernier scale to improve the precision of his instruments, and edited the Almagest, adding figures to illustrate parallax and developing Ptolemy's (second century a.d.) geometrical methods. He also made original contributions to the mathematical analysis of music.

STEPHEN D. NORTON