from a review of 'The Heretics Feast' by Colin Spencer: The first prominent modern vegetarian was the Greek philosopher Pythagoras who lived towards the end of the 6th century BC. The Pythagorean diet came to mean an avoidance of the flesh of slaughtered animals. Pythagorean ethics first became a philosophical morality between 490-430 BC with a desire to create a universal and absolute law including injunctions not to kill "living creatures," to abstain from "harsh-sounding bloodshed," in particular animal sacrifice, and "never to eat meat."

The Heretic's Feast: A History of Vegetarianism by Colin Spencer buy direct from amazon.com (USA) amazon.co.uk (UK)

Quotes (according to Ovid):
from The Extended Circle by Jon Wynne-Tyson. Direct link: amazon.co.uk

Alas, what wickedness to swallow flesh into our own flesh, to fatten our greedy bodies by cramming in other bodies, to have one living creature fed by the death of another! In the midst of such wealth as earth, the best of mothers, provides, nothing forsooth satisfies you, but to behave like the Cyclopes, inflicting sorry wounds with cruel teeth! You cannot appease the hungry cravings of your wicked, gluttonous stomachs except by destroying some other life. - Depicted in Ovid: The Metamorphoses, translated by Mary M.Innes

As long as man continues to be the ruthless destroyer of lower living beings he will never know health or peace. For as long as men massacre animals, they will kill each other. Indeed, he who sows the seed of murder and pain cannot reap joy and love. - attributed by Ovid

Animals share with us the privilege of having a soul. - attributed by Ovid

If men with fleshly mortals must be fed,
And chew with bleeding teeth the breathing bread;
What else is this but to devour our guests,
And barbarously renew Cyclopean feasts?
While Earth not only can your needs supply,
But, lavish of her store, provides for luxury;
A guiltless feast administers with ease,
And without blood is prodigal to please.
attributed by Ovid.

The souls of animals called unreasoning are reasonable, not however with active reasoning powers, because of an imperfect mixture of the bodies and because they do not have the power of speech, as in the case of apes and dogs; for these have intelligence but not the power of speech.

And it is said that Zaratas forbade men to eat beans because he said that at the beginning and composition of all things when the earth was still a whole, the bean arose. And he says that the proof of this is that if one chews a bean to a pulp and exposes it to the sun for a certain time (for the sun will affect it quickly), it gives out the odour of human seed. And he says that there is another and clearer proof: if when a bean is in flower we were to take the bean and its flower, and putting it into a pitcher moisten it and then bury it in the earth, and after a few days dig it up again, we should see in the first place that it had the form of a womb, and examining it closely we should find the head of a child growing with it.

Pythagoras laid down the doctrine of the monad and of foreknowledge and the interdict on sacrificing to the gods then believed on, and he bade men not to partake of beings that had life, and to refrain from wine. And he drew a line between the things from the moon upwards, calling these immortal, and those below, which he called mortal; and he taught the transmigration of souls from bodies into bodies even as far as animals and beasts.

Pythagoras the Samian, son of Mnesarchos, said that the monad is god, and that nothing has been brought into being apart from this. He was wont to say that wise men ought not to sacrifice animals to the gods, nor yet to eat what had life, or beans, nor to drink wine. And he was wont to say that all things from the moon downward were subject to change, while from the moon upward they were not. And he said that the soul goes at death into other animals.

- from the 1957 IVU Congress souvenir book:

PYTHAGORAS (570-470 B.C.) Philosopher - mathematician - musician. None of his writings are extant, but we know of him through Philolaus (450 B.C.) Iamblichus, Ovid, Plutarch, and other Greek writers.

"It has always been asserted that he had already abandoned the orthodox diet at the age of nineteen or twenty." "As the natural and necessary result of his pure living we are told by Iamblichus, that 'his sleep was brief, his soul vigilant and pure, and his body confirmed in a state of perfect and invariable health.' " "As for his own diet, 'he was satisfied (says Porphyry) 'with honey or the honeycomb, or with bread only, and he did not taste wine from morning to night; or his principal dish was often kitchen herbs, cooked or uncooked. Fish he ate rarely.' "

"Amongst other reasons, Pythagoras" (says Iamblichus) "enjoined abstinence from the flesh of animals, because it is conducive to peace; for those who are accustomed to abominate the slaughter of other animals. as iniquitous and unnatural, will think it still more unjust and unlawful to kill a man or to engage in war."

"Specially, he exhorted those politicians who are legislators to abstain. For if they were willing to act justly in the highest degree, it was indubitably incumbent upon them not to injure any of the lower animals. Since how could they persuade others to act justly, if they themselves were proved to be indulging an insatiable avidity by devouring these animals that are allied to us. For through the communion of life and the same elements, and the sympathy thus existing, they are, as it were, conjoined to us by a fraternal alliance."