Written by: The Editors of Encyclopædia Britannica
“Conciliarism, in the Roman Catholic church, a theory that a general council of the church has greater authority than the pope and may, if necessary, depose him. Conciliarism had its roots in discussions of 12th- and 13th-century canonists who were attempting to set juridical limitations on the power of the papacy. The most radical forms of the conciliar theory in the Middle Ages were found in the 14th-century writings of Marsilius of Padua, an Italian political philosopher who rejected the divine origin of the papacy, and William of Ockham, an English philosopher who taught that only the church as a whole—not an individual pope or even a council—is preserved from error in faith.”
“15th century saw serious attempts to put the conciliar theories into practice. The Council of Constance (1414–18) invoked the doctrine to depose three claimants to the papal throne; it then elected Pope Martin V as sole legitimate successor to St. Peter, thereby effectively healing the Western (Great) Schism (1378–1417). Though this council is recognized by Rome as the 16th ecumenical council, neither was it convened by a legitimate pope nor were its declarations ever formally approved in their totality; the council’s condemnation of John Wycliffe and Jan Hus (pre-Reformation reformers) was approved, but not the decree Sacrosancta espousing conciliarism. The faction-ridden Council of Basel, which opened in 1431, reaffirmed Sacrosancta. The theory has continued to live on, and its theses have influenced such doctrines as Gallicanism, a French position that advocated restriction of papal power.
The first Vatican Council in 1870 explicitly condemned conciliarism. The second Vatican Council (1962–65) asserted that the pope as a member and the head of the college of bishops forms with it at all times an organic unity, especially when the council is gathered in a general council.”