The second division of ancient Christianity may be subdivided into three periods:
I. The Imperial State Church of the Undivided Empire, or until the Death of Theodosius the Great, or to 395.
II. The Church in the Divided Empire until the Collapse of the Western Empire and the Schism between the East and the West arising out of the Monophysite Controversies, or to circa 500.
III. The Dissolution of the Imperial Church of the West and the Transition to the Middle Ages.
In the third period are to be placed the beginnings of the Middle Ages, as the German invaders had long before 500 established their kingdoms and had begun to dominate the affairs of the West. But the connection of the Church of the West, or rather of Italy, with the East was long so close that the condition of the Church is more that of a dissolution of the ancient imperial State Church than of a building up of the mediaeval Church. At the same time, the transition to the Middle Ages, so far as the Church is concerned at least, takes place under the influence of the ancient tradition, and institutions are established in which the leading elements, taken from ancient life, are not yet transformed by Germanic ideas. The East knew no Middle Age. For a history of the Eastern Church other divisions would have to be made, but in a history in which, for practical reasons, the development is traced in Western Christianity, the affairs of the Eastern Church must be treated as subordinate to those of Western Christianity.
For the second division of the history of ancient Christianity, the principal sources available in English are the translations in A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church. Edited by Ph. Schaff and H. Wace. The First Series of this collection (PNF, ser. I) contains the principal works of Augustine and Chrysostom. The Second Series (PNF, ser. II) is for historical study even more valuable, and gives, generally with very able introductions and excellent bibliographies, the most important works of many of the leading patristic writers, including the principal ecclesiastical historians, as well as Athanasius, Gregory of Nazianzus, Gregory of Nyssa, Basil the Great, Cyril of Jerusalem, Hilary of Poitiers, Jerome, Rufinus, Cassian, Vincent of Lerins, Leo the Great, Gregory the Great, and others. These translations are in part fresh versions, and in part older versions but slightly, if at all, revised, taken from the Library of the Fathers of the Holy Catholic Church anterior to the Division of the East and West, Oxford, 1838, et seq.
For the period before the outbreak of the great christological controversies, the ecclesiastical historians are of great value. There are no less than four continuations of the Ecclesiastical History of Eusebius accessible: the ecclesiastical histories of Socrates, 324-439 (ed. R. Hussey, Oxford, 1853); of Sozomen, 324-425 (ed. R. Hussey, Oxford, 1860); of Rufinus, 324-395, which is appended to a Latin version or rather revised and "edited" Latin version of Eusebius; of Theodoret, 323-428 (ed. Gaisford, Oxford, 1854). Fragments of the Ecclesiastical History of the Arian Philostorgius, from the appearance of Arius as a teacher until 423, have been translated and are to be found in Bohn's Ecclesiastical Library. For the period after the Council of Ephesus, A. D.431, there is no such abundance, but Evagrius, of whose history (ed. Parmentier and Bidez, London, 1898) there is a translation in Bohn's Ecclesiastical Library, though not in PNF, is of great value as he gives many original documents; and a portion of the Ecclesiastical History of John of Ephesus (trans. by R. P. Smith, Oxford, 1860) carries the history to about 600. There are also works devoted to the history of the West by Gregory of Tours, the Venerable Bede, and Paulus Diaconus, and others of the greatest value for the third period of this division. They will be mentioned in their place.
As the series of the great church councils begins with the Christian Empire, the History of the Councils, by Hefele, becomes indispensable to the student of ecclesiastical history, not only for its narrative but for the sources epitomized or given in full. It has been translated into English as far as the close of the eighth century, or well into the beginnings of the history of the mediaeval Church. The new French translation should be used if possible as it contains valuable additional notes. In connection with Hefele may be used:
Percival, The Seven Ecumenical Councils, in PNF, ser. II, vol. XIV.
Wm. Bright, Notes on the Canons of the First Four General Councils, 1882, should be consulted for this period. Bruns, op. cit., and Lauchert, op. cit., give texts only.
The two great collections of secular laws are:
Codex Theodosianus, ed. Mommsen and Meyer, Berlin, 1905.
Corpus Juris Civilis, ed. Krueger, Mommsen, Schoell, and Knoll, Berlin, 1899-1902.
The Cambridge Medieval History, vol. I, 1912, covers the period beginning with Constantine and extending to the beginning of the fifth century. It contains valuable bibliographies of a more discriminating character than those in the Cambridge Modern History, and render bibliographical references unnecessary. To this the student is accordingly referred for such matters. The second volume of this work will cover the period 500-850.