The Diet That Had No Name

Start with a phrase that, two hundred years ago, was perfectly ordinary. If someone in eighteenth-century Europe didn't eat meat, people said: he follows the Pythagorean diet. Not "vegetarian" — that word didn't exist yet. Pythagorean. Named after a philosopher who'd lived more than two thousand years earlier.

Pythagoras was born on the island of Samos, off the coast of what's now Turkey, in the sixth century BC. But he founded his school far to the west, in Croton, in southern Italy. It was less a university than a brotherhood: vows, silence for newcomers, shared property — and rules about food. The Pythagoreans believed in the transmigration of souls, the idea that after death a soul moves into another body, including an animal's. From that belief came a very practical problem: if an ox might carry someone's soul, eating an ox becomes complicated.

But the most famous Pythagorean rule isn't about meat at all. It's about beans. Students were forbidden to eat beans, and here's where it gets strange: even in antiquity, nobody quite knew why. Explanations piled up by the dozen. Diogenes Laërtius, a much later biographer of the philosophers, lists several: beans supposedly cause heaviness and a restless spirit in the stomach, or they're somehow connected to the soul, or humans and beans are made of the same substance. Each explanation sounds convincing — right up until you read the next one.

Later writers picked up the thread. Plutarch, a Greek author writing under the Roman Empire, left a short treatise called "On the Eating of Flesh," and it contains a passage still quoted today. He offers the reader a simple test: if you're so sure an animal was made for you to eat, kill it yourself — with your bare hands and teeth, no knife, no club, no axe. Can't do it? Then your certainty is built on something shakier than you thought. A century and a half later, the philosopher Porphyry wrote an entire book on the subject, "On Abstinence from Killing Animals" — no longer a short argument, but a full treatise.

The name for all this, though, is surprisingly recent. On September thirtieth, eighteen forty-seven, in the English seaside town of Ramsgate, in a house called Northwood Villa, people from across England gathered and founded the Vegetarian Society — the first in the world. It was chaired by Joseph Brotherton, a member of parliament for Salford. The word "vegetarian" had already been floating around in print for a few years, but it was this meeting that pushed "Pythagorean" out for good.

Which leaves the bean question. Late in the twentieth century, the American anthropologist Solomon Katz offered an elegant theory: there's an inherited metabolic condition that makes fava beans dangerously toxic to some people, and maybe the ancient taboo was a kind of cultural safeguard against it. The idea got tested — and it fell apart. Pythagoras came from Samos, and his school sat in Calabria, in southern Italy, which happens to be one of the places where that condition is rarest today — by modern estimates, well under two percent of the population. So the question stands open. Two and a half thousand years on, nobody actually knows why the philosopher disliked beans. Sometimes history hands us not an answer, but a beautifully preserved mystery.

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