THE last age of antiquity was an age of yeast. Ideas were in fermentation; religious questions came to be regarded as “interesting”—just as they are now. The spirit of inquiry took the place of placid acceptance on the one hand, and placid indifference on the other. It was natural that there should be a rebound from the effort of Augustus to re-order religion on an Imperial, conventional, and unemotional basis. Then, too, Rome, which had never been really Italian except in the sublime previsions of Virgil, grew every day more cosmopolitan: the denizens of the discovered world found their way thither on business, for pleasure, as slaves—the influence of these last not being the least important factor, though its extent and character are not easy to define. Everything tended to foment a religious unrest which took the form of one of those “returns to the East” that are ever destined to recur: the spiritual sense of the Western world became Orientalised. The worship of Isis and Serapis and much more of Mithra proved to be more exciting than the worship of the Greek and Roman gods which represented Nature and law, while the new cults proposed to raise the veil on what transcends natural perception. No doubt the atmosphere of the East itself favoured their rapid development; the traveller in North Africa must be struck by the extraordinary frequency with which the symbols of Mithraism recur in the sculpture and mosaics of that once great Roman dependency. Evidently the birthland of St. Augustine bred in the matter-of-fact Roman colonist the same nostalgia for the Unknowable which even now a lonely night under the stars of the Sahara awakes in the dullest European soul. Personal immortality as a paramount doctrine; a further life more real than this one; ritual purification, redemption by sacrifice, mystical union with deity; these were among the un-Roman and even anti-Roman conceptions which lay behind the new, strange propaganda, and prepared the way for the diffusion of Christianity. With the Italian peasants who clung to the unmixed older faith no progress was made till persecution could be called in as an auxiliary. [Illustration: _Photo:_ _Mansell._ ASSYRIAN LION AND LIONESS IN PARADISE PARK. British Museum.]