… the decline of political and civic institutions did not mean the decline and destruction of every sort of institution and this is particularly obvious with the survival of the institutional Church. It is important here to stress at the beginning how Roman an institution the Church was by the start of the fifth century. After Constantine (with a brief hiatus under the emperor Julian) the “catholic” church (that is, the institutional Church which conformed to the “right” sort of Christianity) had been the continued recipient of imperial benefaction: emperors built churches and funded Church activity. This was itself very Roman, reflecting a continuation of the role that pagan emperors had played in previous centuries, demonstrating their piety by building temples and reviving old religious practices. The emperors had not “gotten religion” but merely changed religion and so changed their religious benefaction accordingly.

The emperors and the Roman state had also taken an active role beginning in the fourth century in defining exactly what the “right” sort of Christianity was. In response to a dispute over the ordination of bishops in North Africa (the “Donatist” schism), Constantine called a council of bishops to convene in Arles in 314 to resolve the matter (it didn’t work and Constantine began persecuting the remaining Donatists). But that council would hardly be the last – Constantine convoked the first ecumenical council (one that in theory reflected the entire Christian Church) in Nicaea in 325 in order to create a single universal Christian doctrine and resolve a number of internal disputes (having grown as a religion in secret and facing persecution, as you might imagine Christianity had a lot of significant local variations). The emperor Theodosius I (r. 379-395) convened the next major council at Constantinople in 381; after that it was the emperor Theodosius II (r. 402-450) who convened the next at Ephesus in 431 and then the emperor Marcian (r. 450-457) who convened the next at Chalcedon in 451. All of these councils served to define what the “right” Christianity was (“Chalcedonian” Christianity, named after the council), putting some belief systems outside of the doctrine of the Roman Church.

But whereas other Roman institutions didn’t survive the collapse of Roman political authority, the Church as an institution very much did. It was perhaps not obvious that it would – many of the “barbarians” had embraced a non-Chalcedonian Christianity, Arianism, and so might have been hostile to the Church as it existed in Rome. But in practice the need to consolidate the loyalty of their Roman Chalcedonian Christian subjects (on this, note Brown, op. cit. 2nd ed., 105-6, 133-8) and the prestige that the institutional Church held led the rulers of Rome’s successor states to convert to Chalcedonian Christianity; the last of the major Arian Christian kings was Garibald, King of the Lombards in 671.

Indeed, the institutional Church was in some ways a lifeboat in which other elements of the Late Roman world were carried through the storm of the fifth century into the Middle Ages. We’ve already talked about the Church’s role in preserving a fair chunk of the Latin literary tradition. Much of this was done through the spread and then perseverance of monasticism. The first communities of monks emerged in the Eastern Roman Empire in the fourth century and spread through the failing Roman Empire in the fourth and fifth centuries. The Western monastic tradition builds from this with the foundation of Monte Cassino in 529 by Benedict of Nursia and the promulgation of the Rule of Saint Benedict.

Meanwhile, the Church also emerged as one of the central institutions in the cities of the Roman world, with the bishop, the religious head of the Church in a given city, emerging as a key figure in civic governance. While the figure of the bishop rose to importance in both the east and the west, in the east, bishops largely did not move into becoming secular leaders alongside religious figures, in part presumably because the central Roman authority still existed to handle those functions. But in the west, the decline of both civic and centralized government left bishops in the breach. This in turn often preserved older Roman political geography as Liebeschuetz notes, with the civitas surviving as an administrative unit in the form of the diocese of a bishop, precisely because those bishoprics were originally established along Roman administrative lines and remained so even after Roman administration vanished. Bishops ended up taking up some of the tasks that in the past would have fallen to a Roman governor and since they had their seats in the embattled Roman cities, many of those cities survived the difficult fifth and sixth centuries precisely because they were the seat of a bishop.

And in order to run the institution of the Church, its bishoprics and their diocese, it needed both educated clergy who could read the Bible but also administrators who had learned the law – by which they meant Roman law. Secular learning had largely collapsed with the Roman Empire in the west – it had existed to provide training for wealthy men to become secular administrators for the central imperial government and so when the demand for that kind of training vanished, so too did the schools that trained the administrators and jurists. And so the Church had to train them itself, setting up episcopal and monastic schools which trained theology, but also law and administration (and of course provided the context for that survival of Latin literature as a teaching tool). As levels of education and literacy among the secular elite declined, it made sense for kings to employ bishops and other members of the clergy as members of their own administration, leading to this distinctly Roman religious institution having a key place within the secular “barbarian” kingdoms that followed.

Bret Devereaux, “Collections: Rome: Decline and Fall? Part II: Institutions”, A Collection of Unmitigated Pedantry, 2022-01-28.