In the Middle Ages the theory that human reason was to be placed above faith found able exponents, and more than once men arose who questioned some of the fundamental principles of Christianity, or who went farther still by rejecting entirely the Christian revelation. But such views were expounded in an age when the outlook of society was markedly religious, and they exercised no perceptible influence on contemporary thought. Between the fourteenth century and the eighteenth, however, a great change had taken place in the world. Dogmatic theology had lost its hold upon many educated men. The Renaissance movement ushering in the first beginnings of literary and historical criticism, the wonderful progress made in the natural sciences, revolutionising as it did beliefs that had been regarded hitherto as unquestionable, and the influence of the printing press and of the universities, would in themselves have created a dangerous crisis in the history of religious thought, and would have necessitated a more careful study on the part of the theologians to determine precisely the limits where dogma ended and opinion began. But the most important factor in arousing active opposition to or studied contempt of revealed religion was undoubtedly the religious revolution of the sixteenth century, and more especially the dangerous principles formulated by Luther and his companions to justify them in their resistance to doctrines and practices that had been accepted for centuries by the whole Christian world. They were driven to reject the teaching authority of the visible Church, to maintain that Christ had given to men a body of doctrines that might be interpreted by His followers in future ages as they pleased, and to assert that Christians should follow the dictates of individual judgment instead of yielding a ready obedience to the decrees of Popes and Councils. These were dangerous principles, the full consequence of which the early Reformers did not perceive. If it was true, as they asserted, that Christ had set up no visible authority to safeguard and to expound His revelation, that for centuries Christianity had been corrupted by additions that were only the inventions of men, it might well be asked what guarantee could Luther or Calvin give that their interpretation of Christ's doctrine was correct or binding upon their followers, and what authority could they produce to warrant them in placing any dogmatic restrictions upon the freedom of human thought? The very principles put forward by the Reformers of the sixteenth century to justify their rejection of certain doctrines were used by later generations to prepare the way for still greater inroads upon the contents of Christianity, and finally to justify an attitude of doubt concerning the very foundations on which Christianity was based. Empiricism, Sensualism, Materialism, and Scepticism in philosophy, undermined dogmatic Christianity, and prepared the way for the