The account of an event as reported by an admirer is bound to be different from the description of the same event as preserved by a critic. This indeed is as true of the council of Chalcedon and the split which it engendered in the Church as any other incident in history. Whereas scholars in the western world have sought to perpetuate a more or less appreciative view of the council, there are churches in the east which from those ancient times to this day have categorically repudiated it. What is attempted in the present work is not a defence of either of these two positions. In fact, while being critical of the pro-Chalcedonian point of view, it expresses disagreement with the traditional standpoint adopted officially by the non-Chalcedonian churches on a few significant points. It contains, in short, the author's findings made on the basis of a study of the relevant documents in their originals, and it endeavours to show that the story of Chalcedon as it has been propagated by the western and the Byzantine ecclesiastical traditions needs clearly to be modified. It implies also the plea that the decisions taken in ancient times with reference to the Christological controversy, whatever justification men in the past may have seen in them, have to be re-examined and reappraised in our times. This work has a history of its own. Its author, a member of one of the Orthodox churches of the east which have refused to accept the council of Chalcedon, has had his initiation into the study of Church history by his reading of the Syriac works on the subject by Gregory Bar Hebraeus and Michael the Syrian. This had enabled him to be conversant with the issues connected with the council of Chalcedon in a particular way. Subsequently, by the reading of the works of Duchesne, Kidd, Hefele, and others, he became acquainted with the pro-Chalcedonian version of the Christological controversy. But it is only during his studies both at the Union Theological Seminary, New York, and at the Yale University Divinity School between the years 1953 and 1957 that he could work with the documents referred to by western historical scholars. He was introduced to this study by the Very Reverend Professor Georges Florovsky of the Byzantine Orthodox Church and guided in his research by Professor Robert L. Calhoun of the Yale University, to both of whom he is most sincerely grateful. Under the direction of the latter the author wrote his Ph.D. dissertation on the Council of Chalcedon and the Christology of Severus of Antioch which the Yale University Graduate School accepted in 1957. Although some of the materials in the dissertation have been adapted and used in the present work, this is an independent book prepared after a great deal of further study and experience. During this latter period of study the author has utilized, in addition to the Serampore and Bangalore libraries in India and the Addis Ababa Library, the Bodleian Library, Oxford; the British Museum Library, London; the Library of the Ecumenical Institute, Bossey; and the Library of the Jesuit College, Louvain. In this way he has worked with the Greek documents relating to the council of Chalcedon in Schwartz instead of Mansi which he had used earlier, most of the documents in Syriac published since the time he had completed his Ph.D. dissertation by the Corpus Scriptorum Christianorum Orientalium and Patrologia Orientalis, and a number of studies on the subject brought out in the western world during the last several decades. Since 1964 the author has taken part in almost all the various meetings of the Unofficial Consultation of Theologians of the Eastern (Byzantine) and the Oriental (Non-Chalcedonian) Orthodox Churches, as well as in two meetings of the latter and the Roman Catholic Church presenting papers in each of them. The papers prepared for and read at the former meetings have all been published in the Greek Orthodox Theological Review, Brookline, Massachusetts,