Isidore of Kiev, also known as Isidore of Thessalonica (Greek: Ἰσίδωρος τοῦ Κιέβου; Russian: Исидор; Ukrainian: Ісидор; b. Thessalonica, 1385-d.Rome, 27 April 1463) was a Greek Metropolitan of Kiev, cardinal, humanist, and theologian. He was one of the chief Eastern defenders of reunion at the time of the Council of Florence,[1].

Early life

He arrived at Constantinople, became a monk, and was there made hegumenos of the monastery of St Demetrius. He knew Latin well, and had considerable fame as a theologian. He was also an accomplished orator; he seems from the beginning to have been eager for reunion with the West.

It was the time when the Court of Constantinople, on the eve of its final destruction by the Turks, was considering the chance of rescue from the Western princes as a result of reuniting with Rome. In 1434 Isidore was sent to Basle by John VIII Palaiologos (1425-1448) as part of an embassy to open negotiations with the Council of Basle. Here he made a mellifluous speech about the splendour of the Roman Empire at Constantinople. On his return he continued to take part in all the preparations for reunion among his own people.

Metropolitan of Kiev

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In 1437, Isidore was appointed Metropolitan of Kiev and Moscow and all Rus' by Emperor John VIII Palaeologus to draw the Russian Orthodox Church into communion with the Roman Catholic Church and secure Constantinople's protection against the invading Ottoman Turks. Grand Prince Vasili II met the new Metropolitan with hostility. However, Isidore managed to persuade the Grand Prince to ally with Catholicism for the sake of saving the Byzantine Empire and the Orthodox Church of Constantinople.

After Isidore had received funding from Vasili II, he went to Florence to attend the continuation of the Council of Basel in 1439. He was made a cardinal-presbyter and a papal legate for the provinces of Lithuania, Livonia, all Russia and Galicia (Poland). During this Council, Isidore fervently defended the union between the Churches of East and West, but he was opposed only by the secular representative from Russia - ambassador Foma (Thomas) of Tver. Finally, the union agreement was signed and Isidore returned to Russia. In 1437 he was sent by the Byzantine Patriarch Joseph II (1416-39, a conspicuous friend of reunion, who died a Catholic at Florence) to be Metropolitan of Moscow As soon as he arrived he began to arrange a Russian legation for the council about to be held at Ferrara. The Russian tsar, Vassili II (1425-62), made difficulties about this, and let him go eventually only after he had promised to come back with "the rights of Divine law and the constitution of the holy Church" uninjured. Syropulus and other Greek writers charge Isidore with perjury because in spite of this he accepted the union.

Council of Ferrara

Isidore set out with a great following on 8 September, 1437, travelled by Riga and Lübeck, and arrived at Ferrara on 15, August, 1438. On the way he offended his suite by his friendly conduct towards the Latins. At Ferrara and at Florence, whither the council moved in January, 1439, Isidore was one of the six chief speakers on the Byzantine side. Together with Johannes Bessarion he steadfastly worked for the union, and never swerved afterwards in his acceptance of it.

After the council, Pope Eugene IV made him his legate for all Russia and Lithuania. On his way back news reached Isidore, at Benevento, that he had been made Cardinal-Priest of the Title of Ss Peter and Marcellinus. This was one of the few cases at the time in which a person not of the Latin Rite was made a cardinal.

From Buda, in March 1440, he published an encyclical calling on all Russian bishops to accept the union, but when he at last arrived in Moscow (Easter, 1441), and proclaimed the union in the Kremlin church, he found that the Grand Duke Vasily II of Moscow and most of the bishops and people would have none of it. Then, at Vasily's command, six Russian bishops met in a synod, deposed Isidore, and shut him up in prison.


In September of 1443, after two years of imprisonment, Metropolitan Isidor escaped to Tver, then to Lithuania and on to Rome. He was graciously received by the pope in 1443. Pope Nicholas V (1447-1455) sent him as legate to Constantinople to arrange the reunion there in 1452, and gave him two hundred soldiers to help the defence of the city. On 12 December of that year he was able to unite three hundred of the Byzantine clergy in a celebration of the short-lived reunion.

He saw the taking of the city by the Turks on 29 May, 1453, and only escaped the massacre by dressing up a dead body in his cardinal's robes. While the Turks were cutting off its head and parading it through the streets, the real cardinal was shipped off to Asia Minor with a number of insignificant prisoners, as a slave. Afterwards he wrote an account of the horrors of the siege in a letter to Nicholas V[2].

He escaped from captivity, or bought himself free, and came back to Rome. Here he was made Bishop of Sabina, presumably adopting the Latin Rite. Pope Pius II (1458-64) later gave him two titles successively, those of Latin Patriarch of Constantinople and Archbishop of Cyprus, neither of which he could convert into real jurisdiction. He was Dean of the Sacred College of Cardinals from October 1461.

The Russian princes denounced the union with Rome, but Isidore persisted. On his return from Italy, during his first Pontifical Divine Liturgy in the Cathedral of the Dormition in the Moscow Kremlin, Isidore had a Latin Rite crucifix carried in front of the procession and named Pope Eugene IV during the prayers of the liturgy. He also read aloud the decree of unification. Isidore passed a message to Vasili II from The Vatican, containing a request to assist the Metropolitan in spreading the Union in Russia. Three days later Isidore was arrested by the Grand Prince and imprisoned in the Chudov Monastery. He was denounced by certain Russian clergymen, who were under pressure of Vasili II, for refusing to renounce the union with "heretical Rome".


  1. Encyclopedia Britannica, Isidore of Kiev, 2008, O.Ed.
  2. Patrologia Graeca, CLIX, 953.


  • Исидор (митрополит) in online Russian Biographical Dictionary (in Russian)
  • Histories of the Council of Florence describe the adventures of Cardinal Isidore.
  • Ludwig Pastor, Geschichte der Paepste, I (3rd and 4th ed., Freiburg im Br., 1901), 585, etc., and his references.
  • The Monumenta Hungariae historica, XXI, 1, contain two versions of the letter to Nicholas V (pp. 665-95, 696-702); see Krumbacher, Byzantinische Litteraturgeschichte (Munich, 1897), 311
  • Strahl, Geschichte der russischen Kirche, I (Halle, 1830), 444
  • Frommann, Kritische Beitraege zur Geschichte der Florentiner Kircheneinigung (Halle, 1872), 138 seq.
  • Hefele, Conciliengeschichte, VII (Freiburg im Br., 1886), passim.

This article incorporates text from the Catholic Encyclopedia of 1913, a publication now in the public domain.

External links

See also

Preceded by
Gerasimus of Kiev
Metropolitan of Kiev
Succeeded by
Gregory II (Bulgarian)
Preceded by
Gregory Mammas
Latin Patriarch of Constantinople
Succeeded by
Johannes Bessarion