Pythagorean Number Mysticism

c. 6th–5th century BCE · Croton / Magna Graecia

First attested

5th century BCEFragments of Philolaus and Aristotle, Metaphysics Book I (985b–988a).

Ancient Greek cosmological doctrine asserting that numbers are the formal archetypes of all reality.

In sixth-century BCE Magna Graecia, Pythagoras and his disciples formulated the foundational doctrine that "all things are number" (arithmos). The school assigned distinct metaphysical and moral qualities to the numbers of the decad (1 through 10): the Monad represented indivisible unity and origin; the Dyad duality and polarity; the Triad harmony and completion; and the Tetrad cosmic justice and stability. Synthesised in the sacred Tetractys—a triangular figure of ten points summing 1 + 2 + 3 + 4—number mysticism became the cornerstone of Platonic cosmology, Renaissance occult philosophy, and Western esoteric metaphysics.