 His most influential work was "Kyrios Christos", an attempt to explain the origins of devotion to Christ as the product of second century Hellenistic forces, and is still the most widely influential academic work on early Christology, even if its conclusions are not supported by modern scholarship.He began his studies at the University of Erlangen, where he met Ernst Troeltsch (1865–1923), with whom he would maintain a friendship that would last throughout his career.Later on, he studied at Leipzig, where he was student of Adolf von Harnack (1851–1930), and afterwards continued his education at the University of Göttingen.