On the 29th of June 1408 he and seven of his colleagues broke away from Gregory XII., and together with six cardinals of the obedience of Avignon, who had in like manner separated from Benedict XIII., they agreed to aim at the assembling of a general council, setting aside the two rival pontiffs, an expedient which they considered would put an end to the great schism of the Western Church, but which resulted in the election of yet a third pope.
He was now an old man of seventy-seven years, honoured with the friendship of princes, recognized as the most distinguished of Italian humanists, courted by pontiffs, and decorated with the laurel wreath and the order of knighthood by kings.
The great schism of the west had already lasted thirty years, and the efforts which had been made to restore unity within the Church by the simultaneous resignation of the two rival pontiffs had been in vain, when in the spring of 1408, the state of affairs being desperate, the idea arose of assembling a council to effect a union without the co-operation of the popes.
Both the deposed pontiffs protested against the legality of the council of Pisa; each had numerous partisans, and the thesis, constructed rather to meet the exigencies of the case,.
In some cases, as in Rome, the pontiffs kept a kind of register, not merely of religious history, but of important political events as well.