German Protestant theologian who clarified the origin and authorship of early Christian literature, particularly the apocryphal acts of various apostles in his Die Apokryphen, Apostelgeschichten und Apostellegenden (1883–87; “Apocrypha, Acts, and Legends of the Apostles”). He also investigated the history of the early papacy and held that St. Peter never lived in Rome. His moderately liberal theology was principally expressed in his Philosophie und Religion (1885), in which he integrated aspects of Kantian Idealism with systematic theology.