The Rema, Rabbi Moshe Isserless, took the Sephardic Shulchan Aruch by Yosef Caro and keyed on differences that applied to Ashkenaz. Thus his entries in the Shulchan Aruch are a crucial Ashkenazic resource. But he was also a central figure in developing Jewish Europe. Rabbi Berel Wein explores the Rema's life and historical times as he helped 16th- century Polish Jewry solidify as a community.