Baeck, Leo(lā`ō bĕk), 1873–1956, German rabbi and scholar. He studied at the conservative Jewish Theological Seminary of Breslau and then at the liberal Hochschule für die Wissenschaft des Judentums in Berlin, also attending the universities of Breslau and Berlin; at Berlin he studied philosophy under Wilhelm Dilthey. He held positions as rabbi in Oppeln (1897–1907), Düsseldorf (1907–12), and Berlin (1912–43). In 1943 he was sent to the Theresienstadt concentration camp. After being liberated in 1945, he moved to London, becoming president of the World Union for Progressive Judaism; he also taught occasionally at the Hebrew Union College in Cincinnati. Baeck's works in English translation include The Essence of Judaism (1905, tr. 1936), The Pharisees and Other Essays (1947), and Judaism and Christianity (1958). In This People Israel (1955, tr. 1965), he propounded his belief in the eternal dialectical polarity between "mystery" and "command," the latter being the divine instructions that give concrete expression to the "mystery" in terms of man's obligations to others, which he defined as piety.
See A. H. Friedlander, Leo Baeck, Teacher of Theresienstadt (1968).