Conciliarism was a movement in the 14th-, 15th- and 16th-century Catholic Church which held that supreme authority in the Church resided with an ecumenical council, apart from, despite, or even if opposed by, the pope.
The movement emerged in response to the Western Schism between rival popes in Rome and Avignon. It was proposed that both popes abdicate in order to allow a new election that implemented a proposal where government supporters of the popes withdraw allegiance and thus prepare the way for a new election. The schism led to the summoning of the Council of Pisa (1409), which failed to end the schism, and the Council of Constance (1414–1418), which had more success, but which also proclaimed its own superiority over the Pope. Conciliarism reached its apex with the Council of Basel (1431–1449). The eventual victor in the warring movements was the pope and the institution of the papacy: the pope's power and teaching authority was confirmed by the condemnation of conciliarism at the Fifth Lateran Council (1512–1517). The apex of the theory of papal authority, on the other hand, was probably reached with the adoption of the doctrine of papal infallibility, promulgated (ironically) by the First Vatican Council (1870).
