Though statistics from the early centuries are elusive, the literature of the period offers scattered yet compelling glimpses into the steady and astonishing diffusion of Christianity across the Roman Empire and beyond. The following primary sources and scholarly works provide the essential framework for tracing the growth of the Church from a persecuted minority to a dominant spiritual force.
I. Sources
While no comprehensive data exists from the ante-Nicene age, various writers furnish vital references that reveal the early Church’s expansion:
- Pliny the Younger (c. 107): Epistulae X.96–97 — his correspondence with Emperor Trajan contains one of the earliest external attestations to the presence and influence of Christians in Bithynia.
- Ignatius of Antioch (c. 110): Ad Magnesios, chapter 10 — testifies to the Church’s growing structure and influence.
- Epistle to Diognetus (c. 120): Chapter 6 — presents the moral distinctiveness of Christians amidst a pagan world.
- Justin Martyr (c. 140): Dialogue with Trypho, chapter 117; First Apology, chapter 53 — speaks of widespread Christian presence.
- Irenaeus of Lyons (c. 170): Against Heresies I.10; III.3–4; V.20 — documents the doctrinal consistency of the Church across distant regions.
- Tertullian (c. 200): Apology I.21, 37, 41, 42; To the Nations I.7; To Scapula 2, 5 — boldly claims the faith has permeated every corner of the empire.
- Origen (d. 254): Contra Celsum I.7, 27; II.13, 46; III.10, 30; De Principiis IV.1.2; Commentary on Matthew — reflects the apologetic engagement with contemporary critiques and the visibility of the Church.
- Eusebius (d. 340): Ecclesiastical History III.1; V.1; VII.1; VIII.1; IX–X — chronicles the Church’s growth through persecution and martyrdom.
- Rufinus: Ecclesiastical History IX.6 — later Latin version of Eusebius, reflecting continued interest in Christianity’s development.
- Augustine (d. 430): City of God — especially insightful for the mature reflection on Christianity’s triumph and universal claim.
II. Works
Scholars and historians have drawn upon the above sources to map the remarkable expansion of the Church in space and influence. The following studies are of particular note:
- Mich. Le Quien: Oriens Christianus (Paris, 1740, 3 vols.) — a masterwork of ecclesiastical geography detailing the Christian East under the patriarchates of Constantinople, Alexandria, Antioch, and Jerusalem.
- Mosheim: Historical Commentaries (ed. Murdock), Vol. I, pp. 259–290 — provides an early Protestant perspective on the Church’s territorial and institutional development.
- Edward Gibbon: Decline and Fall of the Roman Empire, Chapter XV — skeptical in tone but richly informative regarding Christian demographics and public policy.
- A. Beugnot: Histoire de la destruction du paganisme en Occident (Paris, 1835, 2 vols.) — a prize-winning study chronicling the decline of pagan religion in the West.
- Etienne Chastel: Histoire de la destruction du paganisme dans l’empire d’Orient (Paris, 1850) — awarded by the French Academy for tracing the Eastern Church’s spiritual conquest.
- Neander: History of the Christian Religion and Church (trans. Torrey), Vol. I, pp. 68–79 — offers theological reflection alongside narrative development.
- Wiltsch: Handbuch der kirchlichen Geographie und Statistik (Berlin, 1846), Vol. I, p. 32 ff. — a detailed reference work on ecclesiastical spread.
- Charles Merivale: The Conversion of the Roman Empire (Boyle Lectures, 1864) and History of the Romans under the Empire — explore the sociopolitical environment in which Christianity expanded.
- Edward A. Freeman: The Historical Geography of Europe (1881), Vol. I — essential background for understanding the territorial changes relevant to Church growth.
- Friedländer: Sittengeschichte Roms, Vol. III, p. 517 ff. — studies Roman society and the conditions that facilitated Christian expansion.
- Ernest Renan: Marc-Aurèle (1882), Chapter XXV — includes reflections on the geographic and social penetration of Christianity.
- V. Schultze: Geschichte des Untergangs des griechisch-römischen Heidenthums (Jena, 1887) — examines the decline of classical religion and the rise of Christian influence.
Together, these sources and studies form a foundational guide to understanding the missionary triumph and cultural integration of early Christianity as it moved from marginality to empire-wide momentum.
