Metaphysics

The Book of Healing

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Avicenna

c. 1027

The Book of Healing — Kitab al-Shifa — is the most ambitious philosophical encyclopaedia of the medieval world, a work so vast and systematic that it has no real precedent in Islamic or Western philosophy. Despite its title, the book is not primarily a medical text: it is a complete philosophical system covering logic, the natural sciences (physics, astronomy, mineralogy, botany, zoology), mathematics, music, and metaphysics — with psychology and theology as its culminating subjects. Avicenna composed it over approximately two decades at the beginning of the eleventh century, drawing on and transforming the entire Aristotelian corpus through a Neoplatonic lens. Its metaphysical sections — on being, essence, existence, and the nature of God — became the primary source for Islamic, Jewish, and Christian Scholastic philosophy. The famous flying man thought experiment, Avicenna's proof of the soul's independence from the body, appears in the psychology section.