Hippasus of Metapontum

A Pythagorean of Metapontum whose name survives less for what he proved than for what he allegedly revealed: that the ratio of a square's diagonal to its side cannot be expressed as a fraction. In a brotherhood that treated number as the fabric of the cosmos, that discovery was not a triumph but a scandal, and the stories of his death — drowning at sea, a tomb erected in his absence — read like philosophy's first casualty report. He matters because his fate dramatizes the moment abstract inquiry collides with a community's need for harmony, a tension that runs through the whole succession of thinkers Diogenes catalogues.