According to tradition, in the early days of ancient Rome, King Numa Pompilius established a religious institution: the Vestal Virgins. The Vestal Virgins were chaste priestesses of Vesta, the goddess of home and hearth. Their duty was to maintain the sacred flame in the temple of Vesta. The Romans believed that as long as the sacred flame was maintained, Rome would prosper, but that if it should ever be untended, it would lead to Rome’s destruction. The rites of the Vestal Virgins were faithfully maintained throughout the centuries.
Until 394 CE, when on order of the Christian emperor Theodosius, those rites were discontinued and the virgin priestesses dismissed. For many pagans living at the time, this abandonment of an ancient order, along with the associated forsaking of the ancient gods of Rome, were why the western empire fell on hard times in the 400s CE, eventually collapsing completely by 476. Rome in particular was sacked by 410. (Don’t get too spooked by this. Rome was also sacked much earlier in its history in 387 BCE, presumably despite the efforts of the Vestal Virgins.)
Since then, there have been many theories about why the western empire fell. Of course, one plausible narrative is that the empire’s external enemies simply became strong enough to collectively overwhelm it. Under this narrative, the invasion of the Huns in Europe was pivotal, along with the pressure the Eastern Empire was under from the Sasanian Empire that prevented it from sending aid to the west. In this view, the fall of the Western Empire is more about the ferocity of the Huns than anything else.
But there’s always been a sense that the empire rotted from within. Much of the speculation about the fall looks at events in the empire going as far back as its founding in 27 BCE. But looking at developments in the first, second, or third centuries, when the empire continued to function for centuries afterward, has long struck me as little more than an excuse to indulge in moral grandstanding. Often this type of speculation says more about those doing it than anything about ancient history.
The fact is that the Roman Empire was never an ideal state. From the beginning it was a military dictatorship that lurched from one succession crisis to another, often resulting in civil war. On many occasions the empire fragmented among multiple leaders proclaimed emperor by their local legions.
The real question isn’t what caused the empire to fall, but how it managed to hold together through all of these crises. Civic virtue doesn’t appear to be what held it together. Some other quality was important. Something that must have changed in the later part of its history. (At least in the western half. The external enemy narrative seems more compelling for the Eastern Empire’s later fall in 1453 CE.)
I think through much of its history, there was a sense in the empire that it was civilization, while the rest of the world was alien and barbaric, or maybe that the Greco-Roman civilization was the only one worth having. Perhaps another way of saying this is that the culture of the empire was very different from the neighboring regions. This distinction between the empire and its neighbors, this shared identity, may have been enough, despite frequent upheavals, for the people of the empire to repeatedly piece it back together again.
Until the century from 376 to 476 CE. During that period, the Western Empire lost control of its borders and countryside, and long before its “official” fall in 476, ceased to be an effective state. What changed?
I think the answer is Christianity. Now, this isn’t a polemic against the Christian faith. Contrary to what Edward Gibbon and others might have thought, I doubt there was anything in the Christian
doctrine* beliefs in the afterlife or ethics that, in and of itself, weakened the empire. To counter that suggestion, we only have to look at all the successful Christian societies that have existed since then, including for many centuries, the Eastern Empire (aka the Byzantine Empire).
But I think there are a couple of important aspects of Christianity worth considering. The first is that it was exclusive. To be a Christian was to forsake all other gods and religions. (Early Christians were often called “atheists” by their pagan contemporaries because they denied all but one of the gods.) That was unusual in the ancient world. Most pagan religions didn’t really care whether you worshiped other gods. The only other known religion that did was Judaism.
But Judaism didn’t share the second important aspect of Christianity, its evangelistic nature. Christianity was both exclusive and expansionist, a faith that encouraged adherents to find converts, one that saw its mission as bringing as many people into the fold as possible. This combination meant that every time Christianity gained a convert, paganism lost an adherent. In other words, these aspects of Christianity is what made pagan religions easy pickings for it.
Contrary to traditional Christian narrative, there was nothing miraculous in the spread of Christianity. Bart Erhman in his book, The Triumph of Christianity, points out that it only took a modest growth per year, compounded across centuries, for Christianity to become a substantial minority of the empire’s population by the end of the third century with millions of adherents.
Prior to that period, the empire had never persecuted Christians in any consistent sustained manner, but that changed in the closing decades of that century. Until then, Christianity had been an oddball fringe cult, but its growth was bringing it increasingly into mainstream society, along with a perception of its threat to the traditional cults. The persecutions in these decades, under the emperor Diocletian, would become known as the Great Persecution.
Students of history know that the persecutions ended in 313 CE under the first Christian emperor, Constantine. For a few decades, the empire was more or less tolerant of multiple faiths. But in the latter part of the fourth century that started to change, perhaps as a reaction to the last pagan emperor who tried to reverse Christianity’s ascent. As the number of Christians increased, the empire became increasingly intolerant of paganism, culminating in emperor Theodosius declaring Christianity to be the only legitimate religion in 380 CE.
The roles from a century earlier were now reversed. Paganism found itself persecuted, and engaged in a losing cultural battle. According to Erhman, by 400, half the empire was Christian. But the other half remained pagan. Consider what this must have done to the society, what the consequences must have been for its social cohesion.
And Ehrman points out that the western half of the empire was actually behind the east in its conversion rates. In other words, there were more pagans in the west, indicating that proclamations of Christianity as the only legitimate religion were probably far more traumatic there than in the east.
Finally, consider that Christianity had already spread across the borders into the Germanic tribes. This meant that when those (Christian) tribes were fleeing the Huns, looking for refuge inside the borders of the empire, many Christians within the empire may have felt more affinity with them than with Roman pagans. The cultural distinction between the empire and its neighbors, along with the shared identity, at least in the west, was no more. (There remained a strong cultural distinction in the east, particularly after the rise of Islam, which may be why it endured for another millenia.)
Of course, this is admittedly speculation on my part. One of the problems with talking about the cause of a civilization’s collapse, is that a society’s decline and fall is usually not a time when detailed and careful records are kept. Ultimately, we may never know the real reason. Indeed, it’s almost certainly wrong to talk in terms of any one reason when there were probably a multitude of causal factors. But this explanation strikes me as more plausible than most I’ve heard.
Or we could just blame the Huns.
* Edited wording to address Steve Ruis’ point in the comments.