Ethical considerations have always attracted many of the world's greatest personalities to adopt a vegetarian diet. Pythagoras, famous for his contributions to geometry and mathematics, said, "Oh, my fellow men, do not defile your bodies with sinful foods. We have corn, we have apples bending down the branches with their weight, and grapes swelling on the vines. There are sweet-flavored herbs, and vegetables which can be cooked and softened over the fire, nor are you denied milk or thyme-scented honey. The earth affords a lavish supply of riches, of innocent foods, and offers you banquets that involve no bloodshed or slaughter: only beasts satisfy their hunger with flesh, and not even all of those, because horses, cattle, and sheep live on grass." The biographer Diogenes tells us that Pythagoras ate bread and honey in the morning and raw vegetables at night. He would also pay fisherman to throw their catch back into the sea.
In an essay titled "On Eating Flesh," the Roman author Plutarch wrote: "Can you really ask what reason Pythagoras had for abstinence from flesh? For my part I rather wonder both by what accident and in what state of mind the first man touched his mouth to gore and brought his lips to the flesh of a dead creature, set forth tables of dead, stale bodies, and ventured to call food and nourishment the parts that has a little before bellowed and cried, moved and lived. How could eyes endure the slaughter when throats were slit and hides flayed and limbs torn from limb" How could his nose endure the stench? How was it that the pollution did not turn away his taste, which made contact with sores of others and sucked juices and serums from mortal wounds? It is certainly not lions or wolves that we eat out of self-defense; on the contrary, we ignore these and slaughter harmless, tame creatures without stings or teeth to harm us. For the sake of a little flesh we deprive them of sun, of light, of the duration of life to which they are entitled by birth and being."
He then delivered this challenge to flesh-eaters: "If you declare that you are naturally designed for such a diet, then first kill for yourself what you want to eat. Do it, however, only through your own resources, unaided by cleaver or cudgel or any kind of ax."