Not only were the gods of Egypt and Asia never supplanted like those of Gaul or Spain, but they soon crossed the seas and gained worshipers in every Latin province. Isis and Serapis, Cybele and Attis, the Syrian Baals, Sabazius and Mithra were honored by brotherhoods of believers as far as the remotest limits of Germany. The Oriental reaction that we perceive from the beginning of our era, in studying the history of art, literature, and philosophy, manifested itself with incomparably greater power in the religious sphere. First, there was a slow infiltration of despised exotic religions, then, toward the end of the first {23} century, the Orontes, the Nile and the Halys, to use the words of Juvenal, flowed into the Tiber, to the great indignation of the old Romans. Finally, a hundred years later, an influx of Egyptian, Semitic and Persian beliefs and conceptions took place that threatened to submerge all that the Greek and Roman genius had laboriously built up. What called forth and permitted this spiritual commotion, of which the triumph of Christianity was the outcome? Why was the influence of the Orient strongest in the religious field? These questions claim our attention. Like all great phenomena of history, this particular one was determined by a number of influences that concurred in producing it. In the mass of half-known particulars that brought it about, certain factors or leading causes, of which every one has in turn been considered the most important, may be distinguished.