Bk XV:60-142 Pythagoras's Teachings: Vegetarianism.
There was a man here, Pythagoras, a Samian by birth, who had fled Samos and its rulers, and, hating their tyranny, was living in voluntary exile. Though the gods were far away, he visited their region of the sky, in his mind, and what nature denied to human vision he enjoyed with his inner eye. When he had considered every subject through concentrated thought, he communicated it widely in public, teaching the silent crowds who listened in wonder to his words, concerning the origin of the vast universe, and of the causes of things; and what the physical world is; what the gods are; where the snows arise; what the origin of lightning is; whether Jupiter, or the storm-winds, thunder from colliding clouds; what shakes the earth; by what laws the stars move; and whatever else is hidden; and he was the first to denounce the serving of animal flesh at table; the first voice, wise but not believed in, to say, for example, in words like these:
"Human beings, stop desecrating your bodies with impious foodstuffs. There are crops; there are apples weighing down the branches; and ripening grapes on the vines; there are flavoursome herbs; and those that can be rendered mild and gentle over the flames; and you do not lack flowing milk; or honey fragrant from the flowering thyme. The earth, prodigal of its wealth, supplies you with gentle sustenance, and offers you food without killing or shedding blood.
Flesh satisfies the wild beast's hunger, though not all of them, since horses, sheep and cattle live on grasses, but those that are wild and savage: Armenian tigers, raging lions, and wolves and bears, enjoy food wet with blood. Oh, how wrong it is for flesh to be made from flesh; for a greedy body to fatten, by swallowing another body; for one creature to live by the death of another creature! So amongst such riches, that earth, the greatest of mothers, yields, you are not happy unless you tear, with cruel teeth, at pitiful wounds, recalling Cyclops's practice, and you cannot satisfy your voracious appetite, and your restless hunger, unless you destroy other life!
But that former age, that we call golden, was happy with the fruit from the trees, and the herbs the earth produced, and did not defile its lips with blood. Then birds winged their way through the air in safety, and hares wandered, unafraid, among the fields, and its own gullibility did not hook the fish: all was free from trickery, and fearless of any guile, and filled with peace. But once someone, whoever he was, the author of something unfitting, envied the lion's prey, and stuffed his greedy belly with fleshy food, he paved the way for crime. It may be that, from the first, weapons were warm and bloodstained from the killing of wild beasts, but that would have been enough: I admit that creatures that seek our destruction may be killed without it being a sin, but while they may be killed, they still should not be eaten.
From that, the wickedness spread further, and it is thought that the pig was first considered to merit slaughter because it rooted up the seeds with its broad snout, and destroyed all hope of harvest. The goat was led to death, at the avenging altar, for browsing the vines of Bacchus. These two suffered for their crimes! What did you sheep do, tranquil flocks, born to serve man, who bring us sweet milk in full udders, who give us your wool to make soft clothing, who give us more by your life than you grant us by dying? What have the oxen done, without guile or deceit, harmless, simple, born to endure labour?
He is truly thankless, and not worthy of the gift of corn, who could, in a moment, remove the weight of the curved plough, and kill his labourer, striking that work-worn neck with his axe, that has helped turn the hard earth as many times as the earth yielded harvest. It is not enough to have committed such wickedness: they involve the gods in crime, and believe that the gods above delight in the slaughter of suffering oxen! A victim of outstanding beauty, and without blemish (since to be pleasing is harmful), distinguished by sacrificial ribbons and gold, is positioned in front of the altar, and listens, unknowingly, to the prayers, and sees the corn it has laboured to produce, scattered between its horns, and, struck down, stains with blood those knives that it has already caught sight of, perhaps, reflected in the clear water.
Immediately they inspect the lungs, ripped from the still-living chest, and from them find out the will of the gods. On this (so great is man's hunger for forbidden food) you feed, O human race! Do not, I beg you, and concentrate your minds on my admonitions! When you place the flesh of slaughtered cattle in your mouths, know and feel, that you are devouring your fellow-creature."