Ibn Sina (known in Europe as Avicenna, 980–1037) was born near Bukhara, memorised the Qur'an before he was ten, made his reputation as a physician at sixteen, and worked at courts in Iran and Central Asia all his life. He wrote roughly 450 works across philosophy, astronomy, chemistry, and psychology; some 240 survive. He became the most influential figure in bringing Aristotelian philosophy into Islamic thought.

His most famous work is al-Qanun fi al-Tibb — the "Canon of Medicine". It was completed around 1025. The five-book encyclopaedia gathered into one systematic frame all the medicine of Greek, Indian, Persian, and Arab traditions up to its time: anatomy, diseases, pharmacy, nutrition, the spread of epidemics. The book followed the Galenic framework — disease as imbalance — but added many original observations, from clinical signs to pharmacology. The recognition that contagious diseases can travel through water and soil, that tuberculosis is contagious, and that certain visual features of urine indicate kidney disease all stem from Ibn Sina.

In the 12th century Gerard of Cremona translated the Canon into Latin. From that moment it entered the curriculum of the newly-founded medical faculties of Paris, Bologna, Montpellier, and Padua, where it held its place until the middle of the 17th century. Even in Newton's time, European medical students were still reading the Canon. This continuity is exceptional: the same book served as the standard medical text in two very different civilisations — Damascus and Paris — for six centuries.

Ibn Sina also profoundly shaped European scholastic philosophy, including Aquinas, through his works on logic and metaphysics. His "floating man" thought experiment (a person suspended in a void with no sensory input would nonetheless be aware of their own existence) raised the problem of self-awareness six hundred years before Descartes.