The simple version of Code of Hammurabi.

“An eye for an eye” is one of the most famous phrases in law — and it’s nearly 3,800 years old. It comes from the Code of Hammurabi, a set of 282 laws carved into a towering pillar of black diorite in ancient Babylon around 1754 BCE. It is the most complete legal code to survive from the ancient world, and it reveals a civilization that had already worked out something profound: justice should be written down, where everyone can see it — even if what it said depended on who you were.

The stele itself is a monument to the idea of public law. Over two meters tall, crowned with a carving of King Hammurabi receiving authority from the sun-god Shamash, it was set up in a public place so that any Babylonian could — in theory — read the laws that governed them. The prologue is pure royal propaganda: Hammurabi, chosen by the gods, bringing justice to the land. The epilogue curses anyone who would deface or alter the laws. Between them, the 282 provisions cover everything: theft, assault, trade, marriage, divorce, inheritance, wages, liability for collapsed houses and goring oxen. It is a complete operating manual for a Bronze Age society.

The famous severity is real — but it’s more sophisticated than it looks. The lex talionis, the law of retaliation (“if a man destroys the eye of another man, they shall destroy his eye”), applied between social equals. Babylonian society had three classes — the awilum (free landowners), the mushkenum (commoners), and slaves — and the penalty for the same injury varied by the victim’s class. Knock out the eye of a commoner and you paid silver; knock out a slave’s eye and you paid half his value to his owner. It was not equality before the law. But it was something almost as radical for its time: proportionality, written down, applied by judges rather than left to blood feud. The punishment fit the crime, and the crime’s price was fixed in advance.

Many of the laws are startlingly modern in spirit. A builder whose house collapsed and killed the owner could be put to death — an ancient version of criminal liability for negligence. A surgeon who botched an operation faced having his hand cut off — malpractice law with teeth. Wages were regulated, prices were set, and a woman could divorce, own property, and run a business. Other laws are alien: trial by ordeal, where the accused was thrown into the river and judged by whether the gods let them live.

The stele’s own story is an adventure. It was carved in Babylon, but it was found in Susa, in modern Iran — carried off as war booty around 1150 BCE when the Elamites sacked Babylon. There it stood for three thousand years until a French expedition under Jacques de Morgan excavated it in 1901. It now stands in the Louvre, where millions of visitors pass a stone that once told an entire civilization what justice meant.

Hammurabi didn’t invent law — earlier codes existed — but his is the one that survived whole, and its central idea survived with it: that law should be public, fixed, and applied to rich and poor alike, even imperfectly. “An eye for an eye” began as a limit on vengeance — you may take an eye, but only an eye. Civilization, it turns out, started with telling people exactly how far their revenge was allowed to go.