In our time the Church appears constantly as a subject of theological reflection alike in the Evangelical and the Catholic world. Indeed hardly any other question has occupied the minds of theologians so much. At the turn of the century it was still possible to deliver a course of lectures on “the Nature of Christianity” without entering into serious discussion of the Church at all, for it was not considered a real problem. It is different to-day. Robert Grosche says in the Pilgernde Kirche (1938, p. 23): “The religious problem of Christianity to-day lies in the nature and reality of the Church.… He who inquires about Christianity inquires about the Church.”