In Defensor Pacis, disputes the claim that the Pope is the successor to St. Peter, and as the Vicar of Christ on earth exercises "plenitude of power" that is coercive power over all things spiritual and temporal. The Pope's claim was based on Christ's commission to Peter that "whatsoever you bind on earth will be bound in heaven; and whatsoever you loose on earth will be loosed in heaven;" together with the Papal Bull, Unam Sanctum This, together with Pope Leo III's crowing of Charlemagne as "Emperor of the Romans," was used by a successor of Popes to claim this plenitude of power. Marsilius disputed this, claiming the Pope had no coercive power whatsoever. He quotes the words of Jesus who said, "My kingdom is not of this world." He further argues that the Pope is not the successor to St. Peter, any more than he was the successor to the other apostles. In fact, he argues that Peter was not the Bishop of Rome, nor was there evidence that he ever was in Rome. The power to appoint church officers belonged, he argued to the "multitude of believers."