The schism that followed Hadrian's death produced a second and more momentous conflict. Frederick, as head of Christendom, proposed to summon the bishops of Europe to a general council, over which he should preside, like Justinian or Heraclius. Quoting the favourite text of the two swords, 'On earth,' he continues, 'God has placed no more than two powers: above there is but one God, so here one Pope and one Emperor. The Divine Providence has specially appointed the Roman Empire as a remedy against continued schism[182].' The plan failed; and Frederick adopted the candidate whom his own faction had chosen, while the rival claimant, Alexander III, appealed, with a confidence which the issue justified, to the support of sound churchmen throughout Europe. The keen and long doubtful strife of twenty years that followed, while apparently a dispute between rival Popes, was in substance an effort by the secular monarch to recover his command of the priesthood; not less truly so than that contemporaneous conflict of the English Henry II and St. Thomas of Canterbury, with which it was constantly involved. Unsupported, not all Alexander's genius and resolution could have saved him: by the aid of the Lombard cities, whose league he had counselled and hallowed, and of the fevers of Rome, by which the conquering German host was suddenly annihilated, he won a triumph the more signal, that it was over a prince so wise and so pious as Frederick. At Venice, who, inaccessible by her position, maintained a sedulous neutrality, claiming to be independent of the Empire, yet seldom led into war by sympathy with the Popes, the two powers whose strife had roused all Europe were induced to meet by the mediation of the doge Sebastian Ziani. Three slabs of red marble in the porch of St. Mark's point out the spot where Frederick knelt in sudden awe, and the Pope with tears of joy raised him, and gave the kiss of peace. A later legend, to which poetry and painting have given an undeserved currency[183], tells how the pontiff set his foot on the neck of the prostrate king, with the words, 'The lion and the dragon shalt thou trample under feet[184].' It needed not this exaggeration to enhance the significance of that scene, even more full of meaning for the future than it was solemn and affecting to the Venetian crowd that thronged the church and the piazza. For it was the renunciation by the mightiest prince of his time of the project to which his life had been devoted: it was the abandonment by the secular power of a contest in which it had twice been vanquished, and which it could not renew under more favourable conditions. [Sidenote: Revival of the study of the civil law.]