教皇不可謬説
In Catholic theology, Jesus, who is the Truth, is infallible, but only a special act of teaching by the church's bishops may properly be called "infallible". According to the First Vatican Council (1869–71) and as reaffirmed at Vatican II (1962–1965), the earthly head of the Catholic Church, the Pope, is infallible when speaking "ex cathedra" on matters of faith and morals (that is, when he explicitly intends to use his papal office to teach the whole Church definitively and irreformably on matters which deal directly with faith and morals). However, papal infallibility does not extend beyond such cases, thus making it possible for a Pope to sin and to be incorrect. Papal infallibility also belongs to the body of bishops as a whole, when, in doctrinal unity with the pope, they solemnly teach a doctrine as true.