教皇不可謬説
In his "Defensor Pacis" (1324), Marsilius of Padua agreed with William of Ockham that the universal Church is a church of the faithful, not the priests. Marsilius focused on the idea that the inequality of the priesthood has no divine basis and that Jesus, not the pope, is the only head of the Catholic Church. Contradicting the idea of Papal infallibility, Marsilius claimed that only the universal church is infallible, not the pope. Marsilius differed from Ockham in his denial to the clergy of coercive power. Later conciliar theorists like Jacques Almain rejected Marsilius's argument to that effect, preferring more traditional clericalism modified to be more constitutional and democratic in emphasis.