Volume 3: 1771 Edition of the Encyclopedia Britannica!
Metempsychosis
Metempsychosis, the doctrine of transmigration, which supposes that human souls, upon leaving the body, become the souls of such kinds of brutes as they most resemble in their manners.
This was the doctrine of Pythagoras and his followers; who, held that the souls of vicious men were imprisoned in the bodies of miserable beasts, there to do penance for several ages, at the expiration whereof they returned again to animate men; but if they had lived virtuously, some happier brute, or even a human creature, was to be their lot. What led Pythagoras to this opinion was the persuasion he had that the soul was not of a perishable nature; whence he concluded, that it must move into some other body upon its abandoning this. Lucan thinks this doctrine was contrived to mitigate the apprehension of death, by persuading men that they only changed their lodgings, and ceased to live only to begin a new life.