Sources: Sefer HaBahir (~1150 AD) — first explicit rabbinic source; the Zohar (multiple passages); R. Isaac Luria’s Sha’ar HaGilgulim (Gate of Reincarnations, ~1572 AD, recorded by Chaim Vital); Joseph Karo, Maggid Mesharim.

Gilgul neshamot (rolling/cycling of souls) is the Kabbalistic doctrine of metempsychosis — the transmigration of souls through multiple lifetimes. It has no explicit basis in biblical or Talmudic literature, which is precisely why the Bahir’s introduction of the concept was theologically revolutionary. The doctrine addresses questions that troubled medieval Jewish theology: why do the righteous suffer? Why are children born with severe afflictions? Gilgul’s answer: the soul is working through obligations and transgressions from previous lifetimes. This provides a theodicy framework that the this-worldly retribution doctrine of Deuteronomy failed to satisfy. Luria’s Sha’ar HaGilgulim is the most detailed treatment: souls can reincarnate into humans, animals, plants, or even inanimate objects (ibbur — temporary possession of a living person’s soul by another soul seeking to complete a mission or repair a sin); dybbuk is the malevolent form of such possession. Each soul has specific tikkun (repair/rectification) to accomplish — a unique spiritual mission requiring one or more lifetimes. Lurianic gilgul integrates with tzimtzum and shevirat hakelim (shattering of the vessels): the cosmic catastrophe scattered divine sparks into material creation, and human souls are those sparks working their way back to their source through lifetimes of mitzvot and teshuvah. Mainstream Orthodox authorities debated gilgul vigorously: Sa’adiah Gaon and Maimonides rejected it; Nachmanides accepted it; the Shulchan Aruch’s author Joseph Karo received mystical teachings from a maggid (spiritual mentor) who confirmed it.