During the last twenty years of the nineteenth century (the age of German naturalism), Christianity, assailed many times since its foundation, was once again the subject of attack. The basis of the anti-Christian attitude was, on the one hand, the contention that the historical substructure of religious beliefs had been shaken; on the other hand, it was claimed that Biblical criticism called for a revelation of the genuineness of the documentary accounts which deal with the early church, its history, and the nature and validity of its dogmas. Often, the battleground shifted to metaphysics. The existence of God, of supernatural powers, or of any supersensuous reality was denied or declared unknowable. Historians, materialistic philosophers, and scientists pressed their attack against the church and sought to destroy all Christian influence on the course of human affairs. Strong and insistent objections of a sociological nature were also advanced to prove the impotence and inefficacy of the social program of the church. Marxian doctrinaires vehemently insisted that religion was the "opiate of the people," that the church was indifferent to man's lot on earth, and that it was therefore in league with the rich and the mighty. But it was not just the history, the metaphysics, and the social doctrines and social program of the church which were being censured; it was the Christian conception of life and Christian spirituality that were assailed; it was, in short, the "whole" of Christianity that its critics hoped to destroy.