Isaac Israeli c. 855 – c. 955

Isaac ben Solomon Israeli was an Egyptian-born Jewish physician and philosopher, often counted as the first medieval Jewish Neoplatonist. He served as court physician to the early Fatimid caliphs in Kairouan in what is now Tunisia. His Latin-translated medical and philosophical works circulated widely in the medieval schools and were known to Aquinas, while his Book of Definitions and Book of Substances articulate a Neoplatonic emanationist metaphysics in dialogue with Aristotelian categories. He lived to a great age and is reported never to have married, devoting his life to medicine and philosophy.

Isaac Israeli ben Solomon was born around 855 in Egypt, in or near the city of Fustat (medieval Cairo), and trained as an oculist before broadening his medical practice. Around 904 he was invited by the Aghlabid rulers to Kairouan in present-day Tunisia, where he served as court physician to the last Aghlabid emirs and to the founder of the Fatimid caliphate, Ubayd Allah al-Mahdi. He never married and reportedly remarked that his medical and philosophical writings would be his lasting children.

His medical works — On Fevers, On Urines, On the Elements, the Book of Foods and Drugs — were translated into Latin in the eleventh century by Constantine the African and circulated as standard texts in the medical schools of Salerno and Montpellier. The philosophical writings, originally in Arabic and known largely through Hebrew and Latin translations, include the Book of Definitions, the Book of Substances, the Book on Spirit and Soul, the Mantua Text, and a Chapter on the Elements.

Israeli is the first significant Jewish philosopher of the medieval Arabic-speaking world. His Neoplatonic metaphysics — God's first creature is matter and form, from which intellect, soul, and nature emanate in descending order — shaped the Jewish philosophical tradition through Solomon ibn Gabirol and the Arabic philosophical reception in Latin scholasticism. He died around 955 at a great age.