One of the strangest facts in history is the rapid decline of Roman power that set in immediately after the Empire had enjoyed such a succession of good rulers as had never before fallen to its lot. The period of eighty-four years which began with the accession of Nerva and ended with the death of Marcus Aurelius has always been regarded, and rightly regarded, as the golden age of Rome. Trajan was, it is true, a warlike Emperor by choice, and Marcus Aurelius the same by necessity, but Rome had never had since its founding any but the briefest intervals of peace. War, in short, was its natural condition, and it had seldom been carried on with more success than it was by Trajan in Dacia and by Aurelius against the Quadi and the Marcomanni. On the other hand, the reigns of Hadrian and Antoninus Pius (117-161) made up together forty-four years, considerably more than what is usually reckoned as a generation, of almost unbroken peace. Yet the good effects of nearly a century of wise rule seemed to vanish almost immediately when the last of the "Good Emperors" passed away. It is true that Aurelius had a deplorably weak and vicious successor.[43] But Commodus was not more contemptible than Caligula, Nero, or Domitian, and Rome had survived their rule without much apparent injury. Some writers have found a cause in a succession of plagues which raged throughout the Empire with an almost unexampled severity, and it is true that the century which followed the year 165[44] was terribly distinguished by this visitation, but no external calamities are sufficient to account for a nation's decay. These causes are to be sought elsewhere, within rather than without, in the life of men more than in the calamities which years of famine or of pestilence inflict upon them. And it is clearly beyond my province to do more than indicate them in the very briefest way. We see signs of what was going on in days when to all appearance the Empire was most flourishing, while it was certainly still pursuing its career of conquest. Virgil writes a great poem to commend the honest healthy toil of a country life to a generation which had ceased to care for it. The cities were more and more crowded, for the luxuries which they put within the reach of even the poorest were more and more sought after, but the country was passing into a desert or a pleasure ground. The farmers or peasants who had formed the backbone of Roman armies had ceased to be; their fields, where they had not gone out of cultivation, were tilled by huge gangs of slaves. Provincial towns which in old days had been strong enough to make treaties on equal terms with Rome were now half in ruins, with a scanty population that barely contrived to exist. With every year things grew worse and worse. And the Empire aggravated the evils which at first it had done much to palliate if not to remedy. It had superseded the Republic, because this had become utterly corrupt;