Pythagoras and the Pythagorean diet

For roughly twenty-three centuries, Europeans who refused to eat meat were said to follow the Pythagorean diet. The phrase outlasted the Roman Empire, the Latin Middle Ages, the Renaissance, and the Enlightenment, and gave way only in 1847, when the founders of the Vegetarian Society at Ramsgate replaced it with a word coined from vegetable. That a single sixth-century BCE philosopher should have named the practice for so long says something about both the durability of his reputation and the thinness of alternative models. This article sketches what can be recovered of Pythagoras’s teaching on animals, traces the ethical argument through the Greek and Roman writers who preserved it, and follows the long afterlife of the “Pythagorean” label.

The historical Pythagoras

Pythagoras of Samos (c. 570 – c. 495 BCE) left no writings. Everything we know of him comes through later sources, the earliest of which are fragments and anecdotes in fifth- and fourth-century authors, and the fullest of which are the three surviving ancient biographies: Diogenes Laertius’s Lives of Eminent Philosophers Book VIII (third century CE), Porphyry’s Life of Pythagoras (late third century CE), and Iamblichus’s longer De Vita Pythagorica (c. 300 CE). All three draw on an already legendary figure, and modern classicists have long warned that separating the historical teacher from the Neopythagorean reconstruction is a difficult, sometimes impossible task.

What the tradition agrees on is this. Pythagoras emigrated from Samos to the Greek colony of Croton in southern Italy around 530 BCE, where he founded a philosophical and religious community organized around mathematical study, musical theory, and a disciplined common life. Members observed a regimen of silences, daily examinations of conscience, and dietary rules. Chief among the rules was abstention from the flesh of animals. A second, more puzzling prohibition — against eating beans (kyamoi) — is equally well attested but has been variously explained, from dietary physiology to religious symbolism to a pun on kyein (to conceive). Aristotle, writing a century and a half later, already reported several competing rationales (Diogenes Laertius, Lives VIII.34).

Metempsychosis as ethical ground

The doctrine that gave the dietary rule its force was metempsychosis, the transmigration of souls. Pythagoras taught that the soul is immortal, that it passes after death into other bodies — human or animal — and that all ensouled creatures are therefore kin. Xenophanes, a contemporary critic, preserved the earliest datable reference to the teaching: Pythagoras, passing a man beating a puppy, is said to have stopped him with the words, “Cease to strike; it is the soul of a friend, which I recognized when I heard it cry” (Diogenes Laertius, Lives VIII.36, quoting Xenophanes fr. 7). Whether or not the anecdote is historical, it captures the logic of the school: to kill an animal for food is to risk killing a kinsman, a former or future human, a being whose interior life is continuous with one’s own.

Porphyry, in his Life of Pythagoras, summarizes the consequence: Pythagoras urged that “all things that have a soul ought to be regarded as kindred” and that the consumption of flesh “accustoms men to slaughter” (Porphyry, Life of Pythagoras 19). The argument is not merely ritual or medical; it is ethical and psychological. The slaughterhouse, on this view, habituates the killer as much as it harms the killed.

Empedocles, Plato, and the ancient inheritance

The Pythagorean ethic moved quickly into the wider Greek philosophical stream. Empedocles of Acragas (c. 494 – c. 434 BCE), a poet-philosopher who claimed to have been in prior lives “a boy and a girl, a bush and a bird, and a dumb fish in the sea” (fr. 117), wrote in his Purifications that the sacrifice of animals is a father unknowingly slaying a son transformed — a direct inheritance from Pythagorean kinship reasoning. Plato, in Republic II (372a-d), described the healthy original city as grain- and fruit-eating, with meat arriving only when luxury corrupts the polis; the Timaeus and Laws contain further echoes of soul-transmigration. Plutarch, in the first century CE, returned to the theme in two short treatises, On the Eating of Flesh (Moralia 993-999), which attack the pretense that humans are natural carnivores: “You ask me on what grounds Pythagoras abstained from eating flesh. For my part I marvel rather by what accident and in what state of mind the first man touched his mouth to gore” (Plutarch, De esu carnium I.1).

The fullest ancient synthesis is Porphyry of Tyre’s On Abstinence from Killing Animals (Peri apoches empsuchon), written around 270 CE as a letter to a fellow Neoplatonist who had returned to meat-eating. The four books marshal Pythagorean, Empedoclean, Platonic, and Stoic materials into a sustained philosophical argument that animals possess logos of a kind, that justice extends to them, and that purity of soul requires dietary restraint. It remains, as Renan Larue observes, a text “whose arguments are still alive” in contemporary animal ethics (Larue, Le végétarisme et ses ennemis, 2015).

Ovid’s Metamorphoses XV

For most of European history the single most widely read ancient statement of the Pythagorean case was not a philosophical treatise but a poem. Ovid closes his Metamorphoses (c. 8 CE) with a long speech placed in Pythagoras’s mouth (Book XV, lines 60-478), some four hundred verses arguing that the earth yields abundance without bloodshed, that cosmic flux makes all bodies temporary lodgings of a common soul, and that to slaughter an ox that has pulled one’s plough is domestic betrayal. “O mortals,” the Ovidian Pythagoras cries, “refrain from defiling your bodies with impious feasts. There are crops; there are apples bending down the branches; there are grapes swelling on the vines” (Ovid, Metamorphoses XV.75-78). Because the Metamorphoses was a core school text from late antiquity through the eighteenth century, generations of European readers first encountered ethical vegetarianism through Ovid’s verse.

The long afterlife of “Pythagorean”

The label stuck. Medieval and early modern writers who criticized meat-eating — Leonardo da Vinci, Thomas Tryon, the seventeenth-century Cartesians who dissented from Descartes’s mechanistic view of animals — all wrote under the Pythagorean banner. Benjamin Franklin, who adopted a meatless regimen in his youth after reading Tryon, called it “the Pythagorean diet” in his Autobiography. Alexander Pope, Bernard Mandeville, and Oliver Goldsmith debated it by that name in the eighteenth century. Howard Williams, whose 1883 compendium The Ethics of Diet introduced a young M. K. Gandhi to the Western tradition, opened his chronological catalog with a chapter on Pythagoras (Williams, Ethics of Diet, 1883).

Colin Spencer, in The Heretic’s Feast (1993), places the Pythagorean school at the origin of Western ethical abstention and argues that every subsequent Mediterranean and European meat-refusal movement — Orphic, Stoic, Manichaean, Cathar, humanist, Romantic — drew on its vocabulary. The word vegetarian was coined at Ramsgate in 1847 in part to signal a modern, secular, health-oriented re-founding, distinct from the religious and metaphysical commitments of the Pythagorean inheritance. The break was real, but incomplete. The ethical core that Porphyry articulated — that animals are kin, that slaughter coarsens the slaughterer, that abundance is available without blood — remains recognizable in contemporary vegan argument.

What we can and cannot say

Scholars disagree about nearly every detail of the historical Pythagoras, and serious work on the ancient sources has to proceed with caution. Whether the master himself ate no flesh at all, or only abstained from certain cuts or ritually slaughtered animals, is contested; Aristotle’s lost On the Pythagoreans appears to have recorded variations. What is not contested is the association. From no later than the fifth century BCE, Greek writers used Pythagoras’s name as shorthand for principled meat-abstention, and that association held, in Latin and then in the European vernaculars, for more than two millennia. In the history of the idea that it is wrong to kill animals for food, Pythagoras is less a proven historical agent than an enduring philosophical fixed point — the figure the argument has been anchored to whenever it has been made.