As the Donatist threat was dying out, the new and more insidious danger of Pelagianism was spreading in unsuspected qarters, and during Augustine's last years was to absorb more and more of his time and effort. In the church, Pelagius guarded himself against the worst charges, partly by mental reservations, and partly by modifications, but never changed his mind, always faithful to his own conception. We must remember the fact that Pelagius laid sole stress on preaching practical Christianity, that is, monastic life, to a corrupt and worldly Christendom, and on depriving it of the pretext that it was immposible to fulfil the divine commands. Bishop Augustine took up' his sharp and restless pen, rejecting these Pelagian doctrines up to his death. Two African synods (Carthage and Milevis) had condemned the heresiarch, and a report of this action was sent to Pope Innocent I from each gathering (Ep. CLXXV-CLXXVII). All of historians recognized that each of these reports is evidently the work of Augustine, though they were sent in the name of several bishops. The Pope answered them in Ep. CLXXXI-CLXXXII, giving the formal condemation which had been requested. Nevertheless we should remember that nothing would be gained by washing dirty linen in public. Pelagius lost, Celestius dissapeared, but Julian circle reject, reviving Pelagianism, at least semi-Pelagianism. In this controversy, Augustine would remain alawys mystical rather than political. The question of nature and grace recurs so frequently in his works of these years that it is evident to see how deeply disturbed Augustine was at the spread of this deadly error. We suppose, that these activities probably represent the climax of Augustine's achievement. Though he was not a historian, Augustine inquired earnestly the sense of history in this problem. No one could be more conscious than Augusitne that History is an enquiry and not a certainty. He found it in the Pelagian controversy. We can say that Christ's words "apart from me, ye can do nothing" (Joh. XV, 5) became the key of human history for Augustine.