But the most powerful cause of the movement was the intense desire for positive religious belief, which had long been growing in the Empire. The period when Roman incredulity reached its extreme point had been the century that preceded and the half century that followed the birth of Christ. The sudden dissolution of the old habits of the Republic effected through political causes, the first comparison of the multitudinous religions of the Empire and also the writings of Euhemerus had produced an absolute religious disbelief which Epicureanism represented and encouraged. This belief, however, as I have already noticed, co-existed with numerous magical and astrological superstitions, and the ignorance of physical science was so great, and the conception of general laws so faint, that the materials for a great revival of superstition still remained. From the middle of the first century, a more believing and reverent spirit began to arise. The worship of Isis and Serapis forced its way into Rome in spite of the opposition of the rulers. Apollonius of Tyana, at the close of the Flavian period, had endeavoured to unite moral teaching with religious practices; the oracles, which had long ceased, were partially restored under the Antonines; the calamities and visible decline of the Empire withdrew the minds of men from that proud patriotic worship of Roman greatness, which was long a substitute for religious feeling; and the frightful pestilence that swept over the land in the reigns of Marcus Aurelius and his successor was followed by a blind, feverish, and spasmodic superstition. Besides this, men have never acquiesced for any considerable time in a neglect of the great problems of the origin, nature, and destinies of the soul, or dispensed with some form of religious worship and aspiration. That religious instincts are as truly a part of our nature as are our appetites and our nerves, is a fact which all history establishes, and which forms one of the strongest proofs of the reality of that unseen world to which the soul of man continually tends. Early Roman Stoicism, which in this respect somewhat resembled the modern positive school, diverted for the most part its votaries from the great problems of religion, and attempted to evolve its entire system of ethics out of existing human nature, without appealing to any external supernatural sanction. But the Platonic school, and the Egyptian school which connected itself with the name of Pythagoras, were both essentially religious. The first aspired to the Deity as the source and model of virtue, admitted dæmons or subordinate spiritual agents acting upon mankind, and explained and purified, in no hostile spirit, the popular religions. The latter made the state of ecstasy or quietism its ideal condition, and sought to purify the mind by theurgy or special religious rites. Both philosophies conspired to effect a great religious reformation, in which the Greek spirit usually represented the rational,