Mediaeval Europe was, in fact, much more of a unity than the modern traveller would expect, and this was mainly due to the influence of the Church. The spiritual unity went deep on one side of man's nature, and when a man like Erasmus surveyed the prospect at the beginning of the sixteenth century we can well understand his horror, and his determined abstention from any step which would precipitate the break-up of the one organized body which represents the old united culture of Christendom and might check the new forces which were threatening selfishness and disorder in ever-widening circles on the globe. For it must be noted that new forces of expansion were making themselves felt, as the unity of the Church was being threatened from within. Explorers were extending, East and West, the sphere in which the European was to impose his influence for good and evil on other peoples, and the sixteenth century thus becomes one, perhaps the most critical, of all the turning-points in the history of the West. Danger was mixed with hope, disorder with new knowledge and fresh power, and the crisis has not yet been surmounted. But we have gained by now some insight into the nature of the new forces and see that they should, and one day will, work more fully in the direction of unity in the civilized world, of healthy independence in the parts and a growing harmony in the whole. Little of this could have been seen by the observer at the outbreak of the Reformation. Nationalism, democracy, colonial expansion, religious change, the growth of knowledge and its application to industry and social reform, these are the salient features which distinguish our modern from the mediaeval world, and we have to consider how far they make for the unity of mankind.