Shneur Zalman of Liadi, the Alter Rebbe

A student of the Maggid, a formidable halakhist who wrote his own Shulchan Aruch, and the founder of Chabad — the branch that insists the intellect must lead. His Tanya (1796) is the movement's only systematic book of doctrine.

The one who made Hasidism argue. Where most of the movement taught in stories and aphorisms, he wrote a book with chapters and a thesis, addressed not to the tzaddik but to the ordinary struggling reader, and told them exactly what rank to aim at. ⚠ He is also, on the mitnagdic side's own evidence, a serious enough posek that the charge of ignorance simply does not stick.