The Metaphysics of The Healing

The metaphysical part of Kitāb al-Shifāʾ, Ibn Sīnā's largest philosophical encyclopedia, in ten books. It first asks what metaphysics studies and answers that its subject is the existent as existent, not God, whose existence it must instead prove. Ibn Sīnā then introduces the primary notions of the existent, the thing and the necessary, which the mind grasps without definition, and draws his famous distinction between what a thing is and the fact that it exists. The middle books treat substance and accident, unity and multiplicity, and universals, including the claim that horseness, considered in itself, is only horseness, neither one nor many. Later books argue that a chain of contingent beings needs a Necessary Existent, one and simple, which knows particulars in a universal way and from which the intellects and the heavenly spheres emanate. The tenth book turns to prophecy, worship, law and the succession to political rule.

It is the main source for Avicenna's proof of God, his distinction between essence and existence and his theory of universals, ideas that dominated later Islamic thought and passed into Latin scholasticism.