Kaplan, Mordecai Menahem (môrˈdĭkĪˌ mənäkhˈəm kăpˈlən) [key], 1881–1983, American rabbi, educator, and philosopher, b. Lithuania, grad. College of the City of New York, 1900, M.A. Columbia Univ., 1902. He came to the United States when he was eight years old. In 1909 he became principal and in 1931 dean of the Teachers Institute of the Jewish Theological Seminary of America. In 1922 he founded the Society for the Advancement of Judaism. He is best known, however, as the originator and leader of the Reconstructionist movement (see Judaism). Among his many books are Judaism as a Civilization (1934, rev. ed. 1957), The Meaning of God in Modern Jewish Religion (1937), Judaism without Supernaturalism (1958), And If Not Now, When? Toward a Reconstitution of the Jewish People (1973).
See I. Eisenstein and E. Kohn, ed., Mordecai M. Kaplan (1952); R. Libowitz, Mordechai M. Kaplan and the Development of Reconstructionism (1984); E. S. Goldsmith et al., ed., The American Judaism of Mordecai M. Kaplan (1992).