1439: Attempt to Unite the Catholic and Orthodox Churches

On this day the unification of the Catholic and Orthodox churches was announced. 

It was the culmination after years of efforts to unite the Christian world in the fight against the common enemy from the east – the Turkish Ottomans, who were already on the verge of conquering Constantinople. 

Even the Byzantine Emperor John VIII Palaiologos was interested in the Union of Churches. 

His Imperial Majesty came personally to Italy, accompanied by 700 people, including the Patriarch Joseph II of Constantinople, 23 Orthodox metropolitans and a large number of theologians.

They attended the Ecumenical Council presided by Pope Eugene IV, also an advocate of the Union of Churches.

During that Council, Catholics and Orthodox coordinated their views on religious questions, especially about the principle of papal supremacy and the doctrine of purgatory. 

However, the most controversy was about the famous phrase “Filioque”, which in the Catholic Church indicates that the Holy Spirit comes from the Father and the Son (Latin: “Patre Filioque”), while the Orthodox claim that comes from the Father through the Son (“Patre per Filium”).

Eventually, the agreement was made and was signed by Constantinople’s Patriarch Joseph II (Patriarch of Constantinople has the status of “primus inter pares” in Orthodoxy and bears the title of the Ecumenical Patriarch). 

The agreement was signed by all the Orthodox metropolitans, except one – Mark of Ephesus. He persisted in his opposition to the pope, and some consider him responsible for the downfall of the whole Union. 

The whole movement finally failed, and Constantinople fell into the hands of Turks less than 14 years later.