German religious writer. As a RC he studied Catholic theology, but in 1919 he joined the Lutheran Church at Uppsala. He was appointed a professor at Marburg in 1922. He became the organizer of a German High Church movement and even founded an Evangelical Order of Franciscan Tertiaries. His principal work, Das Gebet (1918; abridged Eng. tr., Prayer, 1932) is a comprehensive historical analysis of the subject.