GERSHOM BEN YEHUDAH (c. 965–1028), German halakhist and Jewish communal leader. Despite the many uncertainties surrounding Gershom's life and historical role, it is clear that he was the central figure in the crystallization of Ashkenazic learning and communal organization in pre-Crusade Europe. A generation or two after his death Gershom was already termed Maʾor ha-Golah ("light of the exile"), a title reflecting the perception of both his spiritual stature and his historical impact.

Gershom's origins are not known, but it is likely that his immediate ancestry was French. He spent his adult life in Mainz, where in addition to writing commentaries on the Talmud and some liturgical poetry, he trained the men who were to be the mentors of Rashi. Gershom's personal life reflected the most painful experiences of medieval Jewish life: his son (and, according to one report, his wife as well) converted...