Pietistic and mystical movement in Judaism that originated in 18th-century Poland. It was a reaction against rigid legalism and Talmudic learning in favour of a joyful form of worship that served as a spiritual outlet for the common people. Hasidism began with the preaching of the man later known as the Ba'al Shem Tov. Teaching that God was immanent in all things and that piety was more important than scholarship, he won followers known as Hasidim (loyalists). Dov Baer founded the first Hasidic community c. 1710, and countless small communities soon sprang up in Poland, Russia, Lithuania, and Palestine, each led by a zaddik. Communal services were marked by dancing, shouting, and singing, through which participants reached a state of spiritual ecstasy. Though excommunicated from Orthodox Judaism in 1772, the Hasidim continued to flourish. By the 19th century Hasidism had become an ultraconservative movement that was accepted by the Orthodox as legitimate. Huge numbers of Hasidim fell victim to the Holocaust, but their survivors established vital movements in Israel and the U.S. The Lubavitcher sect, based in Brooklyn, N.Y., numbers about 200,000.