From persecution to patronage

By the early fourth century CE, Christianity had grown from a persecuted sect within Judaism to a trans-Mediterranean movement spanning languages, classes, and ethnicities. The persecutions under Diocletian (303–311 CE) had sought to restore the unity of the empire through devotion to the old gods, but they instead underscored the strength of a new, text-based, missionary religion.

In 312 CE, Constantine’s victory at the Milvian Bridge under the sign of the Chi-Rho marked a decisive turn. The Edict of Milan (313) legalized Christianity; by century’s end, under Theodosius I, it became the official faith of the Roman state. Monotheism had become imperial ideology.1

The politics of doctrine

Imperial patronage transformed theology into state policy. When Constantine convened the Council of Nicaea in 325 CE, the issue at stake, Arius’s claim that the Son was subordinate to the Father, was as much political as metaphysical. A divided Church threatened civic order; a single creed promised unity.2

Nicaea’s formulation, that the Son was homoousios (of one substance) with the Father, established the core of Trinitarian orthodoxy. Yet disputes persisted for decades, forcing emperors to act as theologians and bishops as imperial administrators. Monotheism’s triumph thus required continual negotiation between philosophical precision and political cohesion.

Christianizing the cosmos

As pagan temples closed and civic cults declined, Christian thinkers faced the task of explaining a universe once filled with gods. Ambrose, Athanasius, and Augustine presented the Christian God as both Creator and sustainer of the entire cosmos, a deity whose providence embraced every cause. The old pantheon was reinterpreted as the realm of angels and demons; the one divine Logos ordered both nature and history.

This theological re-mapping of the universe also carried cultural consequences: time became linear, directed toward redemption; history acquired moral purpose; and the empire itself was imagined as a vehicle for divine plan.3

The conversion of philosophy

The fourth and fifth centuries witnessed a complex dialogue between Neoplatonism and Christian theology. While pagan philosophers such as Plotinus, Porphyry, and Proclus continued to defend the ancient vision of the One, Christian writers like Augustine of Hippo transformed it. In Augustine’s Confessions and City of God, the ascent to the One became a journey of grace; the Platonic hierarchy of being was baptized into Christian metaphysics.4

The intellectual synthesis of Greek metaphysics and biblical revelation created the enduring grammar of Western theology: God as pure being (esse), creation as dependent participation, and evil as privation rather than substance.

The fall of the gods

By the late fourth and early fifth centuries, the dismantling of the ancient cults was no longer a matter of imperial decree alone but of zealous enforcement by bishops, monks, and Christian mobs. The Theodosian decrees of 391–392 CE had outlawed sacrifice and temple ritual, declaring that “no person shall pollute himself with sacrifices.”5 Yet imperial law itself rarely reached the countryside; it was local activism, not bureaucracy, that brought the gods low.

In Alexandria, the symbolic turning point came in 391 CE, when riots between Christians and pagans culminated in the storming of the Serapeum. Bishop Theophilus, supported by imperial troops and Christian militants, led the destruction of the vast temple complex, desecrating statues and converting its precinct into a church.6Imperial endorsement followed, and what had been the greatest shrine of Greco-Egyptian religion became a triumphal monument to Christian victory.

A generation later, under Cyril of Alexandria (patriarch 412–444), persecution persisted. His turbulent episcopate witnessed the expulsion of Alexandria’s Jews (415) and the brutal murder of Hypatia, the Neoplatonist philosopher and mathematician, by a mob allied with the bishop’s faction.7 The event marked both the symbolic end of classical philosophical life in Alexandria and the fusion of theology with civic power.

Further south, in Upper Egypt, the monk Shenoute of Atripe (c. 347–465 CE) led his followers in raids on rural temples, burning idols and incorporating temple estates into his monastic federation. In his sermons, Shenoute justified violence as warfare against demons inhabiting pagan sanctuaries; his zeal turned imperial policy into grass-roots iconoclasm.8

Similar patterns appeared across the empire. Martin of Tours destroyed rural shrines in Gaul; Porphyry of Gaza petitioned the emperor for funds to level the great Marneion temple. Bishops in Asia Minor and Syria re-consecrated sanctuaries as churches, while the Codex Theodosianus codified penalties for maintaining pagan rites.9By the sixth century, most temples were ruined, their stones reused in churches or monasteries.

The so-called “closing of the temples” was therefore not a peaceful fading of belief but a cultural revolution, enacted through law, violence, and appropriation. Paganism did not die of neglect; it was actively suppressed, its sacred geography overwritten by a Christian one. Shrines became basilicas, festivals became processions, philosophers became saints or martyrs of another age. Out of that destruction arose the first truly Christian landscape of the Mediterranean, a world in which the unity of God was inscribed not only in creed and scripture but also in the very stones of its cities.

Augustine and the two cities

Augustine (354–430 CE) faced a world collapsing under barbarian invasions and moral fatigue. In The City of God, he redefined empire itself: Rome’s destiny was not divine mission but human ambition. True unity lay only in the civitas Dei, the community of souls bound by love of God.10

Augustine’s theology completed the late-antique synthesis. By wedding biblical history to Platonic ontology and ethical inwardness, he established the framework for medieval Christian thought. The Trinity became the archetype of community; history became the arena of salvation.

After empire

When the Western empire fell in 476 CE, its monotheism endured. The Church, not the state, became the carrier of culture. Scripture, creed, and philosophy survived the collapse of administration. In the Byzantine East, the synthesis of Greek language and Christian theology persisted in the liturgy and the writings of Maximus the Confessor and John of Damascus.

By the early medieval period, the unity of God and reason was a common assumption across the Mediterranean. The questions of late antiquity, how the One relates to the many, how divine reason orders the world, would migrate into the schools of Islam, Judaism, and Latin Christendom.

The late-antique legacy

Monotheism’s triumph in the Roman world was more than a religious victory; it was a redefinition of reality. The ancient cosmos of many powers became a universe governed by one law. Philosophy became theology; history became providence. In that transformation lay both the unity and the restlessness of the Western mind.

• 1. H. A. Drake, Constantine and the Bishops: The Politics of Intolerance (Baltimore: Johns Hopkins University Press, 2000), 43–51.
• 2. Lewis Ayres, Nicaea and Its Legacy: An Approach to Fourth-Century Trinitarian Theology (Oxford: OUP, 2004), 82–97.
• 3. Robert Markus, The End of Ancient Christianity (Cambridge: CUP, 1990), 104–117.
• 4. Augustine, Confessions VII.9–21; City of God VIII.10–12.
• 5. Codex Theodosianus 16.10.10 (391 CE).
• 6. Rufinus, Ecclesiastical History 11.22–26; Socrates Scholasticus, Historia Ecclesiastica 5.16–17.
• 7. Edward J. Watts, Hypatia: The Life and Legend of an Ancient Philosopher (Oxford: OUP, 2017), 113–128.
• 8. David Brakke, Athanasius and Asceticism (Baltimore: Johns Hopkins University Press, 1995), ch. 7 “Shenoute and the War on Idols.”
• 9. Glen Bowersock, Hellenism in Late Antiquity (Ann Arbor: University of Michigan Press, 1990), 117–132.
• 10. Augustine, The City of God, XIX.17–24