At the opening of the sixth century, large segments of the Roman Empire had fallen to barbarian warlords. The Churches of Rome and Constantinople were locked in a schism rooted in different attitudes towards the decrees and definitions of the Fourth Ecumenical council held at Chalcedon in 451. The emperor Justinian (527-565) dreamed of reunifying and restoring the Empire; but to accomplish this he needed a unified Church. Before Justinian ascended the throne the schism between Rome and Constantinople had been healed, largely due to Justinian's influence, but a significant segment of the Eastern population (dubbed "monophysites") would not accept the union and the imperial church remained divided. The monophysites rejected union with Rome because they believed that Chalcedon's definition of faith - which was received by Rome as a victory for Roman theology - denied the fundamental conviction that Jesus is the one divine Person of God the Word incarnate. The monophysites adhered rigidly to the christological formulas of St Cyril, bishop of Alexandria (412-444), and they rejected Chalcedon as a betrayal of St Cyril and the Council of Nicea. Hoping that it would facilitate his political aims for the Empire, Justinian vigorously pursued a policy of reconciling the monophysites to the council of Chalcedon, and thereby to Rome. He sponsored in Constantinople a theological programme to show that the language of Chalcedon's definition of faith was faithful to the meaning, if not to the exact terminology, of Cyril's christological formulas. The three documents translated in this volume are significant as imperial documents reflecting the conclusions reached in that theological programme. Although they failed to convince the monophysites or reconcile them to the imperial church, they are important in that they articulate the interpretation of Chalcedon's christological definition upheld by Orthodox theologians even today, and they set the stage for the christological definitions of the Fifth Ecumenical Council. They therefore serve as an important source which sets forth fundamental philosophical principles underlying the Orthodox doctrine concerning the Person of Jesus Christ.