Didascalicon, Book IV: the order and number of the divine books
Chapter XII. That there are four principal synods
Among the other councils there are four venerable synods which principally embrace the whole faith, like the Gospels, or the same number of rivers of paradise. Of these the first, the Nicene Synod of three hundred and eighteen bishops, was held under the emperor Constantine Augustus, in which, the blasphemy of the Arian perfidy being condemned, which the same Arius asserted concerning the inequality of the holy Trinity, the same holy synod defined by the Creed that God the Son is consubstantial with God the Father. The second synod, of one hundred and fifty Fathers, was assembled at Constantinople under Theodosius the elder, which, condemning Macedonius, who denied that the Holy Spirit is God, demonstrated the Holy Spirit to be consubstantial with the Father and the Son, giving the form of the creed which the whole confession of Greeks and Latins proclaims in the churches. The third synod, the first of Ephesus, of two hundred bishops, was held under Theodosius the younger Augustus, which condemned with just anathema Nestorius, who asserted two persons in Christ, showing in two natures one person of our Lord Jesus Christ. The fourth synod, of Chalcedon, of six hundred and thirty priests, was held under the prince Marcian, in which it condemned beforehand by one sentence of the Fathers Eutyches, abbot of Constantinople, who pronounced one nature of the Word of God and of the flesh, and his defender Dioscorus, a bishop of Alexandria, and Nestorius again with the rest of the heretics, the same synod proclaiming that Christ God was so born of the Virgin that in him the substance of both the divine and the human nature are confessed. These are the four principal synods, most fully proclaiming the doctrine of the faith. But if there are any councils which the holy Fathers, full of the Spirit of God, have ordained, after the authority of these four they remain established with all vigor, whose acts are contained in this work. Synodus is interpreted from the Greek as company or assembly. The name of council, however, is drawn from Roman custom. For at the time when causes were being tried, all assembled together and treated with common intention. Hence also council is said from common intention, as it were consilium. For cilia are the coverings of the eyes. Hence also considium is consilium, the d passing into l. Coetus is a meeting, or a gathering from coming together, that is assembling into one. Hence it is also called conventus, as conventus, coetus, concilium, from the society of many into one. Epistola in Greek is interpreted missa in Latin. The canonical epistles, that is regular, which are also called catholic, that is universal; because they were written not to one people or city only, but to all nations generally. The Acts of the Apostles set in order the beginnings of the Christian faith among the nations and the history of the nascent Church, and are called of the apostles. Apocalypse is interpreted from Greek into Latin revelation, according to what John says: The Apocalypse of Jesus Christ, which God gave unto him, to make known to his servant John (Apoc. 1).