The Elements of Theology

A systematic summary of Neoplatonic metaphysics set out in 211 numbered propositions, each with a proof, in the manner of Euclid's geometry. It begins from the claim that every plurality participates in some way in unity, and builds a single ordered picture of reality flowing from the One, which is also the Good. Every productive cause is superior to what it produces. Everything caused remains in its cause, proceeds from it and turns back towards it, a triple movement of remaining, procession and return that structures the whole system. Proclus then works down through the levels of reality: the divine unities he calls henads, intellects, and souls, explaining how each level participates in the one above, and ending with the descent and ascent of individual souls. Abstract and compressed, it gave later readers a compact map of late Platonism, and a work derived from it, the Book of Causes, carried its ideas into Arabic and Latin thought.

It is the most systematic statement of late ancient Neoplatonism, and through the Book of Causes and later Christian writers it fed medieval metaphysics.