The relationship of Christianity to paganism is, therefore, a very complex subject, and it would not be possible in this place to work out one tithe of it. Nor is it needed. The two cardinal facts with which we are now concerned are the principle of antagonism and the practice of toleration. As to the former there need not be any discussion on the fact. Everywhere throughout Europe its effect is to be seen. It formed the most solid and systematic arresting force against the natural development of pagan belief and practice, and it is this fact of arrested development in pagan belief and practice which is of great importance. We can ascertain the point of stoppage, note the stage of arrested development, and trace out the subsequent history of a custom, belief, or rite so arrested. As a survival in a state of arrested development, a custom or belief is observable throughout its later history. All it does is to decay, and decay slowly, and each stage of decay may oftentimes be discovered. On the other hand, if no arrest of development had taken place there would have been no survival and no decay. The custom or belief which is not arrested by an opposing culture becomes a part of the religion or of the institutions of the nation, and the history of its development becomes, as a rule, lost in the general advance of religion and politics--custom develops into law, belief develops into religion, rite develops into ceremonial, and tradition ceases to be the force which keeps them alive. The two classes of custom and belief thus contrasted are of different value to the student. The one is important because it contains the germs and goes back to the origin of existing institutions. The other is important because, having been arrested by a strong opposing force, unable to destroy it altogether, it remains as evidence of custom and belief at the time of its arrestment. It will be seen at once how far this evidence may take us. It stretches back into the remotest past. It survives in the stage at which it was arrested, not of course in the form in which it then appeared, but in the decayed form which years of existence beneath the ever-opposing forces of the established civilisation must have brought about.