German-Jewish existentialist and religious philosopher. As a student at Berlin and Freiburg, he rejected the idealism of G. W. F. Hegel. He briefly thought of converting to Christianity, but turned instead to an intensive reading of the Hebrew classics. While serving in World War I he began to formulate the existentialist understanding of faith and belief that would eventuate in his major work, The Star of Redemption (1921). He collaborated on a translation of the Old Testament with M. Buber in which he tried to restore what he thought was the existentialist tone of the original.