Euclid

Almost nothing survives about the man: an ancient Greek mathematician working in Alexandria, active around 300 BC, after Plato's circle and before Archimedes. Later scholars invented colorful backstories; medieval writers confused him with an earlier philosopher. What remains is the work. In the Elements, he synthesized earlier Greek geometry — drawing on Eudoxus, Thales, Theaetetus — and built it into a deductive system, each theorem following from a handful of axioms. He also wrote on optics, conic sections, spherical geometry, and number theory, though many works are now lost. Euclid is gen…