This Open Culture feature explores the life and legacy of Ibn Sina (known in the West as Avicenna), the preeminent philosopher and physician of the Islamic Golden Age. It highlights his two most influential works: The Canon of Medicine, which served as the standard medical textbook in European universities until the mid-17th century, and The Book of Healing, a monumental scientific and philosophical encyclopedia. The article also details his famous “Floating Man” thought experiment—arguably a precursor to Descartes’ Cogito, ergo sum—which attempted to demonstrate the existence of the soul and self-awareness independent of sensory input.