Avicenna — Ibn Sina

Abu Ali al-Husayn Ibn Sina was born around 980 CE near Bukhara in the Samanid Empire, the last great Persian-speaking polity before the Turkic invasions. By his own account in his autobiography — the only one we have from a major medieval scientist — he had memorised the Qur'an by age 10, mastered Aristotelian logic by 16, and was practising medicine at 18. When the Samanid library opened to him at 17 in payment for curing the emir, he wrote, "I read those books, gained their knowledge, and saw what station each man had attained."

The Samanid collapse in 999 CE sent him on a thirty-year exile across the Iranian world — Gorgān, Ray, Hamadan, Isfahan — serving as court physician and vizier wherever he stopped. He died at Hamadan in 1037 CE and is buried there in a modernist mausoleum (1952) by the architect Hooshang Seyhoun.

The Qānūn fī al-Ṭibb, completed around 1025 CE, is a five-volume systematisation of all medical knowledge of its age: Greek (Galen, Hippocrates), Indian (Charaka, Sushruta) and Iranian. Translated into Latin in 12th-century Toledo by Gerard of Cremona, it became the standard textbook of Western medicine — taught at Paris, Bologna, Padua, Montpellier and Oxford. It went through 36 printed Latin editions in the 16th century alone, and was still on the syllabus at Padua in 1650.

"The Canon of Avicenna has remained a medical bible for a longer time than any other work."

Ibn Sina's Kitāb al-Shifāʾ — the "Book of Healing," healing of the soul, not the body — is the most influential philosophical work of the entire span between Aristotle and Aquinas. In it he develops the famous distinction between essence and existence, his proof of God as the Necessary Being, and the Flying Manthought experiment: imagine a fully-grown person created in mid-air with no sensory contact at all — he would still be aware of his own existence. The argument anticipates Descartes' cogito by six hundred years.