Although Pythagoras is chiefly remembered for his discovery of the eponymous “Pythagorean theorem” (the square of the hypotenuse of a triangle equals the sum of the squares of the other two sides), he is also the father of vegetarianism.
Indeed until the late 19th century, when the neologism “vegetarian” was coined, people who lived on a fleshless diet were usually referred to as “Pythagoreans.”
――中略――
He is also the first historically attested figure in Western culture to have founded a society that pursued wisdom for its own sweet sake― philosophia (a term that he is reported to have coined). Meat-eating and materialism were taboo in the Pythagorean brotherhood, not only because the Master considered them to be morally repugnant, but because he felt they interfered with the attainment of theoria (pure contemplation).
The fundamental tenet of the Pythagorean order was the doctrine of the transmigration of souls. Paralleling the Hindus, Pythagoras believed that the soul is condemned to pass through a seemingly endless cycle of rebirth during which it may be successively embodied in all the forms of life that exist on earth.
After each incarnation the soul's conduct in its previous life is judged at a trial in Hades. Here the soul is punished or rewarded according to its deserts.
The verdict determines whether the soul will be allowed to reincarnate as a snake, a deer, a bear, a prince, a slave, or a philosopher (which Pythagoras, not surprisingly, regarded as the highest incarnation).
But the greatest reward that a soul can achieve is to be entirely liberated from the wheel of rebirth, and to return to the state of divine bliss from which it came.
Pythagoras taught that through the transmigration of souls, all the forms of animal life are interrelated.
Precisely because the body of a deer may house the soul of a dear-departed relative, to eat of its flesh would be akin to an act of cannibalism.