Metempsychosis

Metempsychosis, from Greek roots meaning to change ensoulment, names the doctrine that a soul survives bodily death and is reborn into a new body, human or animal, in a repeating cycle. The doctrine enters Greek philosophy through Pythagoras in the sixth century BCE, and ancient sources, including Xenophanes' mocking anecdote of Pythagoras recognizing a dead friend's voice in a beaten dog and asking that it be spared, treat the claim of remembered past lives as a distinguishing, controversial feature of the Pythagorean school from its beginning.

The Orphic religious movement, roughly contemporary with or slightly earlier than Pythagoreanism and closely intertwined with it, held a related doctrine, that the soul is imprisoned in the body as a punishment or a cycle to be escaped through ritual purity and initiation, giving metempsychosis in its Greek form an ethical and soteriological charge beyond simple survival after death. Both traditions treated the cycle as something to be ended rather than affirmed indefinitely, an early and influential instance of transmigration understood as a problem awaiting release rather than a neutral fact about the soul. No writing by Pythagoras himself survives, so everything known of his teaching on the soul comes through later reporters, which is part of why ancient and modern accounts of the doctrine's exact content differ.

Plato took up metempsychosis and gave it its most influential Greek philosophical form, most fully in the myth of Er that closes the Republic and in the Phaedo's argument for the soul's immortality, where souls choose new lives and drink from the river of forgetfulness before rebirth, carrying moral consequences from one life into the conditions of the next.

Later Neoplatonist philosophers preserved and elaborated the doctrine as part of a broader account of the soul's descent into and ascent out of bodily existence. Comparisons to Hindu and Buddhist rebirth doctrines are common and not baseless, since both describe a soul or continuum passing through successive bodies shaped by past conduct, but historians of religion caution against treating metempsychosis as simply the Greek name for the same idea: Pythagorean and Platonic transmigration has no developed doctrine of karma as an impersonal causal law comparable to Indian systems, and unlike Buddhist rebirth it generally assumes a persisting, individual soul rather than a chain of causally linked but non identical states. Whether Pythagoras derived the doctrine from contact with Indian, Egyptian or Orphic sources, or arrived at it independently, remains a question ancient sources debate and modern scholarship cannot settle from the evidence available.