The Bukharan physician-philosopher Ibn Sina (980–1037) wrote the most ambitious work of Eastern philosophy: Kitab al-Shifa, the 'Book of Healing'. The title means healing from ignorance, not from physical illness; the contents run from logic through astronomy and geometry to metaphysics. The metaphysical section shapes Aristotle's inheritance for Islamic philosophy once more: the distinction between necessary and contingent being, essence as distinct from existence, the role of the active intellect within the cosmos. That frame passed directly into later European scholasticism — Aquinas, Duns Scotus, and eventually into modern metaphysics.

The most striking passage in the Shifa is the 'floating man' thought experiment. Imagine a person created as a full-grown adult, blindfolded, suspended in air without any bodily sensation. This person sees nothing, hears nothing, touches nothing; perceives neither their own body nor the outside world. Yet, says Ibn Sina, this person is aware of their own existence. Self-awareness, then, is independent of body and the senses — the soul knows itself directly, without the body.

The argument runs along nearly the same intuitive line as Descartes' cogito, six hundred years earlier. Modern philosophy of mind still wrestles with it: sensory-deprivation thought experiments and the 'brain in a vat' are extensions of Ibn Sina's frame. The Shifa is the first great attempt to weld Aristotelian metaphysics to Neoplatonic psychology in a single system — and it placed the modern problem of self-consciousness, in medieval form, on the philosophical map.