The Roman Republic

In 509 BCE, a group of Roman aristocrats did something that would define their civilization for the next five centuries: they threw out their king and swore never to have another one.

The details come wrapped in legend. The last king of Rome, Tarquinius Superbus — "Tarquin the Proud" — was an Etruscan tyrant whose son, Sextus, reportedly assaulted a noblewoman named Lucretia. She took her own life rather than live with the dishonor. Her kinsman Lucius Junius Brutus carried her body to the Roman Forum, rallied the people, and drove the Tarquin dynasty from the city. Whether this story is history or mythology, the Romans treated it as the founding trauma of their Republic. The hatred of kingship became a kind of national religion.

No modern political scientist would have designed what replaced the monarchy. It was a system of shared power, competing magistracies, and institutional checks so tangled they look accidental. And yet it worked, spectacularly, for roughly 450 years.