The age stretching from the triumph of Constantine to the ascendancy of Gregory the Great marks one of the grandest transitions in the history of Christendom. It is an era in which the persecuted church rose to imperial favor, in which councils convened to settle the great dogmas of the faith, and in which the political and theological destinies of Europe became irrevocably intertwined. The sources for this period are abundant—gleaming with the voices of fathers, emperors, chroniclers, and opponents alike—and they form the bedrock upon which our understanding of this transformative epoch rests.
The Wellspring of Christian Testimony
(a) Foremost among the treasures of this period are the Acts of the Councils, those monumental gatherings where bishops, theologians, and imperial envoys deliberated over the unity of the faith. Preserved in the great Collectiones conciliorum of Hardouin (Paris, 1715 ff., 12 folio volumes), in the vast compilation of Mansi (Florence and Venice, 1759 ff., 31 folio volumes), and in the scholarly repositories of Fuchs and Bruns, these records offer not merely decrees, but the very drama of doctrinal conflict and resolution.
(b) The edicts of emperors—enshrined in the Codex Theodosianus (A.D. 438), the Codex Justinianeus (A.D. 529), and the Codex repetitae praelectionis (A.D. 534)—form another pillar of our evidence, revealing the intricate dance between ecclesiastical authority and imperial law.
(c) Alongside these stand the official letters of popes (collected in the Bullarium Romanum), patriarchs, and bishops, dispatches that speak with the immediacy of men bearing the burden of souls and the weight of nations.
(d) Above all, the writings of the Church Fathers from the dawn of the fourth century to the close of the sixth form a luminous chain of theological reflection and pastoral counsel. Among the Greeks, Eusebius, Athanasius, Basil, the two Gregories, the two Cyrils, Chrysostom, and Theodoret stand preeminent; among the Latins, Ambrose, Augustine, Jerome, and Leo the Great. Their collected works—whether in the stately Benedictine editions, the Maxima Bibliotheca veterum Patrum (Lugdunum, 1677 ff.), or the Bibliotheca veterum Patrum of Gallandi (Venice, 1765 ff.)—remain indispensable.
Chroniclers of the Faith
(e) The age was not without its historians. The Greek church boasts a line beginning with Eusebius of Caesarea († c. 340), whose ninth and tenth books of the Historia Ecclesiastica and his life of Constantine bring us to A.D. 324. Socrates Scholasticus and Hermias Sozomen of Constantinople continue the narrative into the mid-fifth century; Theodoret of Cyros carries it to A.D. 429; Philostorgius, the Arian, offers a partisan view; Theodorus Lector compiles and extends earlier histories to A.D. 518; Evagrius of Antioch writes into the late sixth century. Though Nicephorus Callistus, writing about 1330, lies outside our period, his twenty-three books give a later medieval perspective. These Greek works—save Nicephorus—were often printed together under the title Historiae Ecclesiasticae Scriptores (Paris, 1659–1673; Cambridge, 1720), with the invaluable notes of Valesius and Reading.
In the Latin West, historical production is sparser but not without weight. Rufinus of Aquileia († 410) translated and extended Eusebius; Sulpicius Severus in Gaul wrote his Historia Sacra to A.D. 400; Paulus Orosius, about 416, penned seven books of universal history; Cassiodorus compiled the Historia Tripartita, a digest of the Greek historians, which—together with Rufinus—served as the chief historical source for the entire Middle Ages; Jerome’s De viris illustribus (c. 392) was continued by Gennadius (c. 495) and Isidore of Seville (c. 630).
Chronicles and Computations
(f) The chronological framework of the age is illuminated by works such as the Greek Πασχάλιον or Chronicon Paschale—a computation of Passovers from creation to A.D. 354, later extended to A.D. 628. The Chronicle of Eusebius and Jerome presents an outline of universal history down to 325, with later continuations in Latin by Prosper of Aquitaine (to 455), Idatius of Spain (to 469), and Marcellinus Comes (to 534). These, with others, were gathered in Roesler’s Chronica medii aevi post Eusebium atque Hieron. (Tübingen, 1798).
Voices from the Pagan World
II. No less valuable are the testimonies of non-Christian observers. Ammianus Marcellinus, a soldier under Julian, writes with a candor rare among his contemporaries in his Rerum gestarum (books xiv–xxxi, covering A.D. 353–378). Eunapius, philosopher and bitter critic of Christian emperors, composed a Chronike Historia for A.D. 268–405, now surviving only in fragments. Zosimus, an official under Theodosius II, penned his Historia Nea (six books, A.D. 284–410) with a pronounced pagan bias. To these we may add the writings of Julian the Apostate—polemical yet revealing—and the more urbane works of Libanius and Symmachus, who, though devoted to the old religion, often argued for a philosophical toleration.
All these voices, whether friends of the church or foes, mingle in the great chorus of sources for this period, giving to the historian a rich, if sometimes discordant, symphony of perspectives upon the transformation of the Roman world and the ascendance of Christian civilization.
