While religious phenomena are in some respects singularly constant, they are, nevertheless, as noted for their diversity. While certain essential elements are common to almost all faiths, on the other hand, every individual faith has something peculiar to itself. It not only differs in some respects from other religions, but, as we trace down its history, we find it varying from itself. The Hindoos, Persians, Greeks, Romans, Kelts, Teutons, and Slavs, are shown by philological research to have come originally from a single stock—the primitive Aryan. Their ancestors originally dwelt together in a common home in the neighborhood of the Caspian Sea; and in this ancient time their religion was, probably, one and the same faith, i. e., in substance. Yet how widely diverse have the faiths of these nations come to be, in the four to five thousand years since that ancient home was little by little deserted! How has this diversity come about? What are the forces or influences that differentiate religions?