Pisa, Council of, 1409, unrecognized council of the Roman Catholic Church. It was summoned to end the Great Schism (see Schism, Great) by members of the colleges of cardinals of the two rivals, Gregory XII (in Rome) and Benedict XIII (Pedro de Luna, in Avignon). The plan was to depose both men claiming to be pope and elect a new one. The council had a wide international attendance. It declared both popes to be heretical and schismatic and therefore not popes; the cardinals proceeded to elect Pietro Cardinal Philarghi as Alexander V. This move served to complicate the schism with a third claimant rather than to dissolve it. The council first gave quasi-official expression to the conciliar theory, i.e., that councils are supreme in the church, a notion that became prominent again at Constance and at Basel (see Constance, Council of; Basel, Council of). The lack of recognition toward the council rests on several features; e.g., most of the cardinals involved owed their creation to popes whom they declared to be holding office illegally.