Isaac the Blind

R. Yitzchak Sagi Nahor — Isaac the Blind (c. 1160-1235) — is generally considered the first identifiable Kabbalist in the modern academic sense and the founder of Kabbalah as a teachable textual tradition. The son of R. Abraham ben David (the Ra'avad) of Posquières, he lived in Provence (Languedoc, southern France) at the turn of the 13th century.

His brief Perush Sefer Yetzirah and a small handful of letters to the Geronese kabbalists (R. Yonah Gerondi, R. Ezra, R. Azriel) transmitted the foundational doctrine of the ten sefirot, the ein-sof, and the contemplative discipline that would become Kabbalah. His Geronese students brought the teaching south into Catalonia and Castile, from where it diffused into the wider Sephardic world and ultimately into the Zoharic circle in Castile a generation later. Without Yitzchak Sagi Nahor, there is no Kabbalah.