The Byzantine monk Eutyches (ca. 380-455) preached the doctrine of Monophysitism, the belief that Christ had only a divine nature. His teachings were condemned as heresy by the Council of Chalcedon in 451.
Few facts are known concerning the life of Eutyches. By 450 he was in charge of a large monastery in Constantinople. He was respected for his holiness after long years of prayer and penance, and he had great influence at court through his godson, who was an important official of the emperor. The Church had not fully recovered from the recent theological controversy of Nestorianism, concerning the true personality of Christ. In 431 Bishop Nestorius of Constantinople had been condemned and exiled for teaching that Jesus had, in effect, two personalities, one human, the other divine. Despite Nestorius's condemnation, his followers were not convinced he was wrong. Theodoret of Cyrrhus, a learned and able frontier bishop, had drawn up a formula of reconciliation that described Christ as having a "union of two natures."
In 448 Eutyches protested loudly against Theodoret of Cyrrhus, calling his attempt heretical. Eutyches said he himself professed "the ancient faith." He believed that Jesus was the Son of God, Jesus was God Himself. Jesus, said Eutyches, had only one nature, the divine, which absorbed his humanity. The current bishop of Constantinople, Flavian, condemned Eutyches for misrepresenting Christ, and the controversy—which had simmered for 15 years— boiled over again. Many of the churchmen and political figures who had opposed Nestorius earlier now supported Eutyches, whom they saw as the voice of orthodoxy. Those who had supported Nestorius rallied around Theodoret. Emperor Theodosius II appointed Dioscoros, Bishop of Alexandria and a friend of Eutyches, to preside at a church council called to settle the matter in Ephesus in 449. Pope Leo I sent his legates to the council with clear instructions to denounce Eutyches, whom the pope called "an ignorant, imprudent old man." Dioscoros succeeded in railroading through the council a series of resolutions that completely supported Eutyches. On the emperor's authority he imprisoned all who disagreed. The pope's legates barely escaped to return to Rome and report what had happened.
Pope Leo was furious. The emperor refused to call another council, but within months he died from an accidental fall from his horse. His successor, pressed by the pope, called the general council that met at Chalcedon in 451. This time the tables were reversed. Eutyches was condemned, and his supporter, Bishop Dioscoros of Alexandria, was exiled. The officials of the council described Christ in a way that agreed with neither Nestorius nor Eutyches. Christ, they said, was one person with two separate and distinct natures, united but unmixed. The decisions of this council have been respected since then by all orthodox Christian faiths.
Further Reading on Eutyches
For information about Eutyches the best work is Robert V. Sellers, The Council of Chalcedon (1953), which describes in detail the political and ecclesiastical controversies of his time.