Sedevacantism - Wikipedia

Sedevacantism is the belief that the office of pope of the Roman Catholicism is currently vacant. Sedevacantists are a traditional Catholic segment of Catholicism who insist that recent Popes are heretics for introducing the reforms of the Second Vatican Council, particularly for replacing the Tridentine Roman Missal and its order of Mass with a new one and allowing the celebration of the Mass in the vernacular instead of latin. Their conclusion is based to some extent on the decree of papal infallibility of the First Vatican Council. If a pope promulgates heresy, it is reasoned, he lacks infallibility and thus the office of Pope.

Other sedevacantists argue that some Catholic popes carried out actions that would not be carried out by true popes. Some argue that Pope Paul VI (r: 1963-1978) by abandoning the wearing of the papal crown (called the Papal Tiara) was showing that he was not a valid pope, they arguing that no true pope would have refused to wear the traditional symbol of the papacy. The decision of Pope John Paul I (r: August-September 1978) to abandon the Papal Coronation altogether is seen by such groups in a similar light. One breakaway sedevacantist group, the United States-based true Catholic Church claims that Pope John XXIII (r: 1958-1963) joined the Freemasons in 1935, an act that if true would have earned automatic excommunication and so made him ineligible for the papacy. Other sedevacanists noted that Pope John Paul II (r: 1978-present) declined to take the traditional papal oath and so in their theory was not a valid pope.

Sedevacantism is a subset of Catholic traditionalism. Sedevacantists are opposed by many other Traditionalists, who maintain that the Popes since Pius XII, although they may have personally held many what some traditionalists perceive as scandelous heretical beliefs, nevertheless they were true popes who never tried to use their infallible power (which only is used exceptionally) to promulgate a heresy, which all Catholics believe would be impossible.

A few sedevacantist groups have put forward their own Popes in opposition to those of the Roman Catholic Church. The Palmar de Troya movement, based on what it claimed were a series of apparitions, chose a Spaniard, Pope Gregory XVII as the 'successor' to Pope Paul VI, on the basis that Christ in this supposed apparations had told him that he was to assume the papacy automatically on Pope Paul's death. The true Catholic Church in the late 1990s elected a traditionalist priest to be Pope Pius XIII, claiming that all popes following the death of Pope Pius XII (r: 1939-1958) were invalidly elected or disqualified by virtue of their excommuncation.

Sedevacantists are in fact a very small group, with a membership of only a few thousands, within Roman Catholicism.