You memorized his triangle equation in school, but what if the so-called father of mathematics never proved a single theorem? Meet the real Pythagoras: a charismatic mystic with a golden thigh who believed he was the reincarnation of a Trojan war hero, a fisherman, and a beautiful courtesan.

This deep dive peels back centuries of myth, much of it invented by later Neoplatonists trying to build a pagan icon, to reveal a man who ran a totalizing monastic cult in Croton. We trace how his strange teachings on reincarnation, ritual purity, and the harmony of the spheres shaped Western philosophy and science, even though the famous theorem was known to the Babylonians a thousand years earlier.

• Why almost nothing about Pythagoras is first-hand, and how the Neoplatonists Porphyry and Iamblichus built his legend
• The five-year vow  ...