About this time, Theodore learned that the faith of the Church at Constantinople was greatly disturbed by the heresy of Eutyches. Wishing to preserve the churches of the English that he ruled untainted by this error, he summoned a large number of venerable bishops and teachers to a conference; and when he had carefully ascertained their individual beliefs, he found them all united in support of the Catholic Faith. He therefore took pains to record this fact in a synodical letter, to serve as a reminder and guide to future generations. This letter opens as follows:
‘In the Name of our Lord and Saviour Jesus Christ. On the seventeenth of September in the eighth indiction; in the tenth year of the reign of our most devout lord Egfrid, King of the Northumbrians; in the sixth year of King Ethelfrid of the Mercians; in the seventeenth year of King Aldwulf of the East Angles; and in the seventh year of King Hlothere of the Kentish people. Under the presidency of Theodore, by the grace of God Archbishop of the island of Britain and the City of Canterbury, we the venerable bishops of the island of Britain assembled in conclave at the place which is called in the Saxon language Haethfeld, having the most holy Gospels before us, hereby unite to proclaim the true and orthodox faith. This same faith our Lord Jesus Christ delivered in the flesh to His disciples, who saw Him in person and heard His teaching. This is now set forth in the Creed of the holy fathers, and by all the sacred General Councils, and by the united voice of the accredited doctors of the Catholic Church. We follow them in devotion and right faith, professing our belief in their divinely inspired teachings; and we unite with the holy fathers in acknowledging the Father, the Son, and the Holy Spirit, the Trinity consubstantial in Unity, and Unity in Trinity, that is, One God subsisting in three consubstantial Persons of equal glory and honour.’
And after a great deal more to this effect, in which they affirm their confession of the true Faith, the letter of this holy synod continues: ‘We accept the decisions of the five holy General Councils of the blessed fathers who were acceptable to God; that is, the Council of three hundred and eighteen bishops assembled at Nicaea, which condemned the impious Arius and his teachings; the Council of one hundred and fifty bishops at Constantinople, which condemned the madness of Macedonius and Eudoxius and their teachings; the first Council of two hundred bishops at Ephesus, which condemned the wicked Nestorius and his teachings; the Council of six hundred and thirty bishops at Chalcedon, which condemned Eutyches and Nestorius and their teachings; and the fifth Council at Constantinople in the reign of Justinian the younger, which condemned Theodorus, Theodoret, the epistles of Ibas, and their teachings against Cyril.’
Shortly after this, the letter continues: ‘We also accept the decisions of the Council held in Rome under the blessed Pope Martin in the eighth indiction and ninth year of the reign of the most pious Emperor Constantine [IV]. We glorify our Lord Jesus Christ as they glorified Him, neither adding nor withdrawing anything; we anathematize with heart and voice those whom they anathematized, and accept those whom they accepted. And we glorify God the Father, who is without beginning, and His only-begotten Son, begotten of the Father before all worlds, and the Holy Spirit ineffably proceeding from the Father and the Son, as proclaimed by all the holy Apostles, prophets, and teachers whom we have already mentioned. And we who have all joined with Archbishop Theodore in proclaiming the Catholic Faith affix our signatures hereto.’