or as a being in some other non-human realm of existence. An alternative term is transmigration, implying migration from one life (body) to another. The term has been used by modern philosophers such as Kurt Gödel and has entered the English language. The Greek equivalent to reincarnation, metempsychosis (), derives from meta ('change') and ('to put a soul into'), a term attributed to Pythagoras. Another Greek term sometimes used synonymously is palingenesis, 'being born again'. Rebirth is a key concept found in major Indian religions, and discussed using various terms. Reincarnation, or Punarjanman (, 'rebirth, transmigration'), is discussed in the ancient Sanskrit texts of Hinduism, Buddhism, and Jainism, with many alternate terms such as punarāvṛtti (), punarājāti (), punarjīvātu (), punarbhava (), āgati-gati (, common in Buddhist Pali text), nibbattin (), upapatti (), and uppajjana (). These religions believe that this reincarnation is cyclic and an endless Saṃsāra, unless one gains spiritual insights that ends this cycle leading to liberation. The reincarnation concept is considered in Indian religions as a step that starts each "cycle of aimless drifting, wandering or mundane existence," but one that is an opportunity to seek spiritual liberation through ethical living and a variety of meditative, yogic (marga), or other spiritual practices. They consider the release from the cycle of reincarnations as the ultimate spiritual goal, and call the liberation by terms such as moksha, nirvana, mukti and kaivalya. However, the Buddhist, Hindu and Jain traditions have differed, since ancient times, in their assumptions and in their details on what reincarnates, how reincarnation occurs and what leads to liberation. Gilgul, Gilgul neshamot, or Gilgulei Ha Neshamot () is the concept of reincarnation in Kabbalistic Judaism, found in much Yiddish literature among Ashkenazi Jews. Gilgul means 'cycle' and neshamot is 'souls'. Kabbalistic reincarnation says that humans reincarnate only to humans unless YHWH/Ein Sof/God chooses. History Origins The origins of the notion of reincarnation are obscure. Discussion of the subject appears in the philosophical traditions of India. The Greek Pre-Socratics discussed reincarnation, and the Celtic druids are also reported to have taught a doctrine of reincarnation. Early Jainism, Buddhism, and Hinduism The concepts of the cycle of birth and death, Saṁsāra, and liberation partly derive from ascetic traditions that arose in India around the middle of the first millennium BCE. The first textual references to the idea of reincarnation appear in the Upanishads of the late Vedic period