Reincarnation
Further information: Reincarnation, Gilgul, and KabbalahThe notion of reincarnation, while held as a mystical belief by some, is not an essential tenet of traditional Judaism. It is not mentioned in traditional classical sources such as the Tanakh ("Hebrew Bible"), the classical rabbinic works (Mishnah and Talmud), or Maimonides' 13 Principles of Faith. While one might contend the idea of reincarnation is not outlined in the Tanakh, there exist references to resurrection throughout Isaiah. However, books of Kabbalah — Jewish mysticism — teach a belief in gilgul, transmigration of souls, and hence the belief is universal in Hasidic Judaism, which regards the Kabbalah as sacred and authoritative.
Among well-known Rabbis who rejected the idea of reincarnation are Saadia Gaon, David Kimhi, Hasdai Crescas, Yedayah Bedershi (early 14th century), Joseph Albo, Abraham ibn Daud and Leon de Modena. Among the Geonim, Hai Gaon argued with Saadia Gaon in favour of gilgulim.
Rabbis who accepted the idea of reincarnation include, from Medieval times: the mystical leaders Nahmanides (the Ramban) and Rabbenu Bahya ben Asher; from the 16th-century: Levi ibn Habib (the Ralbah), and from the mystical school of Safed Shelomoh Alkabez, Isaac Luria (the Ari) and his exponent Hayyim Vital; and from the 18th-century: the founder of Hasidism Yisrael Baal Shem Tov, later Hasidic Masters, and the Lithuanian Jewish Orthodox leader and Kabbalist the Vilna Gaon.
With the 16th-century rational systemisation of Cordoveran Kabbalah by the Ramak, and the subsequent new paradigm of Lurianic Kabbalah by the Ari, Kabbalah replaced "Hakirah" (Rationalistic Medieval Jewish Philosophy) as the mainstream traditional Jewish theology, both in scholarly circles and in the popular imagination. Isaac Luria taught new explanations of the process of gilgul, and identification of the reincarnations of historic Jewish figures, which were copiled by Haim Vital in his Shaar HaGilgulim.
In Kabbalistic understanding of gilgul, which differs from many Eastern-religious views, reincarnation is not fatalistic or automatic, nor is it essentially a punishment of sin, or reward of virtue. In Judaism, the Heavenly realms could fulfill Maimonides' Principle of faith in Reward and Punishment. Rather, it is concerned with the process of individual Tikkun (Rectification) of the soul. In Kabbalistic interpretation, each Jewish soul is reincarnated enough times only in order to fulfil each of the 613 Mitzvot. The souls of the righteous among the Nations may be assisted through gilgulim to fulfil their Seven Laws of Noah. As such gilgul is an expression of Divine compassion, and is seen as a Heavenly agreement with the individual soul to descend again. This stress on physical performance and perfection of each Mitzvah is tied to the Lurianic doctrine of Cosmic Tikkun of Creation. In these new teachings, a cosmic catastrophe occurred at the beginning of creation called the "Shattering of the Vessels" of the Sephirot in the "World of Tohu (Chaos)". The vessels of the Sephirot broke and fell down through the spiritual worlds until they were embedded in our physical realm as "sparks of holiness" (Nitzutzot). The reason in Lurianic Kabbalah that almost all Mitzvot involve physical action is that through their performance, they elevate each particular spark of holiness associated with that commandment. Once all the sparks are redeemed to their spiritual source, the Messianic Era begins. This metaphysical theology gives cosmic significance to the life of each person, as each individual has particular tasks that only they can fulfil. Therefore, gilgulim assist the individual soul in this cosmic plan. This also explains the Kabbalistic reason why the future eschatological Utopia will be in this world, as only in the lowest, physical realm is the purpose of creation fulfilled.
The idea of gilgul became popular in folk belief, and is found in much Yiddish literature among Ashkenazi Jews.
Read more about this topic: Jewish Eschatology