Bavarian Church historian. From 1826 to 1873 he was professor of Church history at Munich. At first he held Ultramontane views, but he later mistrusted Roman influence. The Letters of Janus (in conjunction with others, 1869) and Letters of Quirinus (1869–70) revealed him as a formidable critic of the First Vatican Council and of the doctrine of Papal infallibility. After refusing to accept the conciliar decisions, he was excommunicated in 1871. In his later years he largely identified himself with the Old Catholic Churches and worked for reunion (see Bonn Reunion Conferences).