Commonly used for the entry of the soul into a new body or reimbodiment; but etymologically it means the clothing of a monad with a new soul, while metensomatosis means the clothing of that ensouled monad with a new body. The new psychic vesture with which the monad is clothed — its metempsychosis in this case — is evolved from the monad itself.
Metempsychosis is in one sense a transmigration, but transmigration is not necessarily metempsychosis; for transmigration merely means changing or passing over from one condition to another, and therefore may include metensomatosis. Metempsychosis also means that the soul “is an indivisible entity in its inmost essence, which is pursuing a course along its own particular evolutionary path as an individual monad, taking upon itself ‘soul’ after ‘soul’; and it is the adventures which befall the soul, in its assumption of, or assuming, ‘soul’ after ‘soul,’ which in their aggregate are grouped together under this word Metempsychosis.- Rakefet Dictionary
“In ordinary language metempsychosis is supposed to be a synonym for transmigration, reincarnation, pre-existence, and palingenesis, etc., but all these words in the Esoteric Philosophy have specific meanings of their own, and should not be confused” (OG 105).
Metempsychosis (Greek: μετεμψύχωσις) is a philosophical term in the Greek language referring to transmigration of the soul, especially its reincarnation after death.
Generally, the term is only used within the context of Ancient Greek philosophy, but has also been used by modern philosophers such as Schopenhauer and Kurt Gödel; otherwise, the term “transmigration” is more appropriate. The word plays a prominent role in James Joyce’s Ulysses, and is also associated with Nietzsche. Another term sometimes used synonymously is Palingenesia.
Europe before the pre-Socratic philosophers
It is unclear how the doctrine of metempsychosis arose in Greece. It is easiest to assume that earlier ideas which had never been extinguished were utilized for religious and philosophic purposes. The Orphic religion, which held it, first appeared in Thrace upon the semi-barbarous north-eastern frontier. Orpheus, its legendary founder, is said to have taught that soul and body are united by a compact unequally binding on either; the soul is divine, immortal and aspires to freedom, while the body holds it in fetters as a prisoner. Death dissolves this compact, but only to re-imprison the liberated soul after a short time: for the wheel of birth revolves inexorably. Thus the soul continues its journey, alternating between a separate unrestrained existence and fresh reincarnation, round the wide circle of necessity, as the companion of many bodies of men and animals.”
To these unfortunate prisoners Orpheus proclaims the message of liberation, that they stand in need of the grace of redeeming gods and of Dionysus in particular, and calls them to turn to God by ascetic piety of life and self-purification: the purer their lives the higher will be their next reincarnation, until the soul has completed the spiral ascent of destiny to live for ever as God from whom it comes. Such was the teaching of Orphism which appeared in Greece about the 6th century BC, organized itself into private and public mysteries at Eleusis and elsewhere, and produced a copious literature.
In Greek philosophy
The earliest Greek thinker with whom metempsychosis is connected is Pherecydes of Syros; but Pythagoras, who is said to have been his pupil, is its first famous philosophic exponent. Pythagoras probably [imported] it from Egypt.
The real weight and importance of metempsychosis in Western tradition is due to its adoption by Plato. In the eschatological myth which closes the Republic he tells the myth 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 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.