Metempsychosis is a philosophical term in the Greek language referring to the belief of transmigration of the soul, especially its reincarnation after death. It is a doctrine popular among a number of Eastern religions such as Hinduism, Jainism and Druzism wherein an individual incarnates from one body to another, either human, animal, or plant. Generally the term is only used within the context of Greek Philosophy, but has also been used by modern philosophers such as Schopenhauer and Kurt Goedel; otherwise the phrase transmigration is more appropriate. The word also plays a prominent role in James Joyce's Ulysses, and is associated also with Nietzsche. Another term sometimes used synonymously is Palingenesia.
The earliest Greek thinker with whom metempsychosis is connected is Pherecydes; but Pythagoras, who is said to have been his pupil, is its first famous philosophic exponent. Pythagoras probably neither invented the doctrine nor imported it from Egypt, but made his reputation by bringing Orphic doctrine from North-Eastern Hellas to Magna Graecia and by instituting societies for its diffusion.
The real weight and importance of metempsychosis in Western tradition is due to its adoption by Plato. Had he not embodied it in some of his greatest works it would be merely a matter of curious investigation for the Western anthropologist and student of folk-lore. In the eschatological myth which closes the Republic he tells the story how Er, the son of Armenius, miraculously returned to life on the twelfth day after death and recounted the secrets of the other world. After death, he said, he went with others to the place of Judgment and saw the souls returning from heaven and from purgatory, and proceeded with them to a place where they chose new lives, human and animal. He saw the soul of Orpheus changing into a swan, Thamyras becoming a nightingale, musical birds choosing to be men, the soul of Atalanta choosing the honours of an athlete. Men were seen passing into animals and wild and tame animals changing into each other. After their choice the souls drank of Lethe and then shot away like stars to their birth. There are myths and theories to the same effect in other dialogues, the Phaedrus, Meno, Phaedo, Timaeus and Laws. In Plato's view the number of souls was fixed; birth therefore is never the creation of a soul, but only a transmigration from one body to another. Plato's acceptance of the doctrine is characteristic of his sympathy with popular beliefs and desire to incorporate them in a purified form into his system. Aristotle, a far less emotional and sympathetic mind, has a doctrine of immortality totally inconsistent with it.
The extent of Plato's belief in metempsychosis has been debated by some scholars in modern times. Marsilio Ficino (Platonic Theology 17.3-4), for one, argued that Plato's references to metempsychosis were intended allegorically.
In later Greek literature the doctrine appears from time to time; it is mentioned in a fragment of Menander (the Inspired Woman) and satirized by Lucian (Gallus 18 seq.). In Roman literature it is found as early as Ennius, who in his Calabrian home must have been familiar with the Greek teachings which had descended to his times from the cities of Magna Graecia. In a lost passage of his Annals, a Roman history in verse, Ennius told how he had seen Homer in a dream, who had assured him that the same soul which had animated both the poets had once belonged to a peacock. Persius in one of his satires (vi. 9) laughs at Ennius for this: it is referred to also by Lucretius (i. 124) and by Horace (Epist. II. i. 52). Virgil works the idea into his account of the Underworld in the sixth book of the Aeneid (vv. 724 sqq.). It persists in antiquity down to the latest classic thinkers, Plotinus and the other Neoplatonists.
In the short story 'Angelic Butterfly' by Primo Levi, he refers to "Physiological Foundations of Metempsychosis". This is a chapter in a study that proposes that all animals possess that ability to transform like a butterfly.
It is also the title of a longer work by the metaphysical poet John Donne, written in 1601. The poem, also known as the Infinitati Sacrum, consists of two parts, the "Epistle" and "The Progress of the Soule". In the first line of the latter part, Donne writes that he "sing[s] of the progresse of a deathlesse soule".
In the 1996 David Foster Wallace novel Infinite Jest, the mysterious Joelle Van Dyne broadcasts from the MIT college radio station under the on-air name "Madame Psychosis," a play on the term appropriate to the character, who is described as being two different people before and after a freak disfiguring accident (and recovery from crack addiction).