Council of Florence

The Council of Florence was the seventeenth ecumenical council recognized by the Catholic Church, held between 1431 and 1445. It was convened in territories under the Holy Roman Empire. Italy became a venue of a Catholic ecumenical council after a gap of about two centuries (the last ecumenical council to be held in Italy was the 4th Council of the Lateran in Rome's Lateran Palace in 1215). It was convoked in Basel as the Council of Basel by Pope Martin V shortly before his death in February 1431 and took place in the context of the Hussite Wars in Bohemia and the rise of the Ottoman Empire. At stake was the greater conflict between the conciliar movement and the principle of papal supremacy.

The Council entered a second phase after Emperor Sigismund's death in 1437. Pope Eugene IV translated the Council to Ferrara on 8 January 1438, where it became the Council of Ferrara and succeeded in drawing some of the Byzantine delegates who were in attendance at Basel to Italy. Some Council members rejected the papal decree and remained at Basel: this rump Council suspended Eugene, declared him a heretic, and in November 1439 elected an antipope, Felix V.

After becoming the Council of Florence (having moved to avoid the bubonic plague in Ferrara), the Council concluded in 1445 with the promulgation of a decree of union with delegates of the Eastern Orthodox Church.

The union was not universally accepted among the Eastern Christian churches. The delegates of the Georgian Orthodox Church and the Church of Alexandria did not sign the decree of union. The Serbian Orthodox Church rejected the union and was not represented at the council. Although delegates from the Patriarchate of Jerusalem and the Patriarchate of Antioch signed the decree, their patriarchs later rejected the union, maintaining that the delegates had not been authorized to make such commitments on behalf of their churches.

The union also met strong opposition in Constantinople, where the overwhelming majority of both clergy and laity rejected it, accusing the emperor and the patriarch of betrayal. As a result, the attempted resolution of the Great Schism proved short-lived and failed to gain broad acceptance in the Eastern Christian world, despite representing a significant political achievement for the papacy.

In 1447, Sigismund's successor Frederick III commanded the city of Basel to expel the Council of Basel; the rump Council reconvened in Lausanne before dissolving itself in 1449.