448–449

Eutyches, the Tome of Leo the Great and the "Robber Synod" of 449

The aged Constantinopolitan monk Eutyches taught that before the union there were two natures, after it one; he refused to acknowledge Christ as "consubstantial with us". In 448 Flavian and the "Home Synod" condemned him, while Dioscorus of Alexandria, who had made the formula "after the union, one nature" central, supported Eutyches. Leo, bishop of Rome, in his letter to Flavian (the Tome) set out Western christology: the distinctive properties of each nature remain unimpaired and come together in one Person, and the distinction of natures is necessary even after the union; the Word does what befits the Word, the flesh endures what befits the flesh. Leo's christology is grounded in his understanding of salvation: the Mediator must be both human and divine, capable of suffering and impassible. The council at Ephesus in 449, presided over by Dioscorus, did not allow the Tome to be read, acquitted Eutyches and deposed Flavian, Theodoret and other Antiochenes; Leo called it the "Robber Synod".