n. The doctrine that the highest ecclesiastical authority is a church council (rather than a pope).
Conciliarism was a reform 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, or even against, the pope. The movement emerged in response to the Western Schism between rival popes in Rome and Avignon. The schism inspired the summoning of the Council of Pisa (1409), which failed to end the schism, and the Council of Constance (1414–1418), which succeeded and proclaimed its own superiority over the Pope. Conciliarism reached its apex with the Council of Basel (1431–1449), which ultimately fell apart. The eventual victor in the conflict was the institution of the Papacy, confirmed by the condemnation of conciliarism at the Fifth Lateran Council, 1512–17. The final gesture however, the doctrine of Papal Infallibility, was not promulgated until the First Vatican Council of 1870.