The [[First Ecumenical Council|first]] and [[Third Ecumenical Council|third]] ecumenical councils established that Arianism and Nestorianism were heresies and excommunicated the principals, Arian and Nestorius. The excommunication and exile of Nestorius was greatly influence by the Empress [[Pulcheria the Empress|Pulcheria]], the older sister of Emperor Theodosius II, In 441, Theodosius, under the influence of the eunuch Chrysaphius, was convinced to dismiss his sister. Theodosius then began to support the Monophysite error that was promoted by the [[archimandrite]] Eutyches and Dioscorus, an error that Christ not only had one personality but also only one nature.
Domnus, Patriarch of Antioch, was the first to note this error by Eutyches. In November 448, Flavian, the Patriarch of Constantinople, convened a council in Constantinople during which a formal accusation of Eutyches’ error was made against him by Eusebius, [[Bishop]] of Dorylaeum (Phrygia). After hearing Eutyches, the council deposed and excommunicated Eutyches for refusing to admit two natures in Christ after the incarnation.