The idea of Religion as inherently and necessarily old is a compelling one. Religions, after all, presuppose a relationship between the human and the Divine. The idea that this relationship has begun only recently makes little sense. If the Gods are interested in communicating with and helping human beings, then They should have been doing so all along. It also makes no sense to think of this relationship as going through abrupt changes, much less reversals. The idea that the Gods teach human beings first one thing, and then change Their minds and teach something else is internally incoherent - it would be (and consistently has been) rejected out of hand by anyone who accepts the premise that the Gods are interested in and capable of teaching us in the first place.So the notion of any completely and utterly new religion is unreasonable. It would, at least implicitly, assert that the Gods have been either wrong or silent up to a certain point, and then either changed their minds and finally got it right, or went through a change of heart and finally decided to let humans in on what the deal is. All religions at least tacitly accept this constraint - they all seek to locate themselves in the broad sweep of the history of humanity and the cosmos. The most common strategy, to speak crudely, is like that seen with Pan, Cybele, and Santoshi Maa: to defer to tradition and to assert that the "new" teaching being proposed/revealed is confluent with already existing tradition.
But isn't there a possible alternative strategy for the introduction of a new religion? Namely, to proclaim that currently existing religions are wrong and must now be abandoned in favor of the proposed new religion? The error, naturally, is not that of the Gods, but of humanity, who have taken a wrong turn (through no fault of the Divine!) somewhere along the line, but are now being set straight thanks to Divine benevolence. Many people might assume that this is the strategy of, for example, Christianity. The problem, though, is that Jesus, at least so far as we can tell, never proposed any such thing. He was born, lived and died an observant Jew - and he certainly never, ever, intimated anything along the lines of abandoning Judaism.But even though Jesus obviously, and emphatically, did not preach a radical break with the past, this is precisely what his followers, if that is what they were, eventually proposed. Somewhere between Jesus and Constantine a dramatic shift took place: a reform movement within Judaism morphed into a completely new religion, opposed both to Judaism and to all other religions.
By the mid-fourth century, Christianity had not only made the transition to presenting itself to the world as a "new" religion distinct from Judaism, but it was also being aggressively "promoted" (putting it nicely) by the Roman State. Christianity still claimed validity based on Jewish prophecies (and many Christians continue to make such claims to the present day), but as it "spread" (again, this is a very nice way of putting it), it was found that reliance on Jewish scripture alone was not sufficient. Gradually a new theory was put forward by Eusebius, Augustine, Orosius and others - a theory that sought historical validation of Christianity based on the dominant Hellenistic culture of the Roman Empire, and especially the most intellectually prestigious aspect of that culture, Greek philosophy.
The Christians (predictably) faced accusations that they were making precisely the kind of nonsensical claims that we have already talked about: that if in fact their religion was true while all others are false, then their "God" had been inexplicably negligent in waiting so long to reveal the truth! To counter this the Christians put forward the idea that came to be associated with the Latin phrase: Preparatio Evangelica ("Preparation for the Gospel). According to this theory all of human history, leading up to the birth of Jesus, had been "all part of God's plan" for preparing the way, so to speak, for (finally!) revealing the truth (that is, the truth according to the Christian religion).
Eusebius of Caesarea (c.263 - c.339) wrote the first real history of the Christian religion, a biography of the Emperor Constantine, books of Biblical exegesis, a universal history of humanity, and many other works, including a whole book devoted to the subject of Preparatio Evangelica. A good idea of what Eusebius was up to can be gleaned from some of the titles for sections of his book:
Character of the cosmogony of the Greeks
Philosophers' opinions concerning the system of the universe
Why we rejected the opinions of the Greeks concerning the gods
What Plato thought of the theology of the ancients
On the Ideas in Plato
On the first successors of Plato
On the philosophy of Aristotle, and his personal history
On the Stoic philosophy, and the account of First Principles as rendered by Zeno
Numenius the Pythagorean philosopher concerning the Jews
Whew! In fact, there is much, much more. Eusebius drags in the Egyptians, Phoenicians and other "barbarians" as well as, naturally, the Hebrews.The bottom line here is that even though Christians proposed to do nothing less than replace all existing religions with their own, they nevertheless were still forced to try to justify and validate themselves in the usual way - to show that what they were doing, if only looked at from the proper perspective, could be seen as a natural progression from all that had come before!
Early in the fifth century (410 AD - about 70 years after Eusebius died) the city of Rome was sacked by the Visigoths. One of the central tenets of the whole Preparatio Evangelica idea had been that God had, in fact, created the Roman Empire for the express purpose of spreading the Gospel. But now the very capital of the Empire had not only been overrun - but the people who did it were .... Christians! Rome was also a center of Pagan resistance to Christianization, and the Church now faced a chorus of rancor from those who "began to blaspheme against the true God more ferociously and bitterly than before," - or at least that's how it looked to Augustine of Hippo, who, in response, composed his most famous work, The City of God: Against the Pagans.
City of God was a massive literary effort aimed to establish the intellectual credentials, indeed, superiority, of Christendom in the face of a culturally entrenched Paganism composed of people "who were not isolated die-hards," but who were, rather, "the center of a wide intelligentsia," according to Peter Brown, a leading scholar of late antiquity who further states (in his biography Augusine of Hippo): "Quite bluntly, the Pagans were the 'wise' men, the 'experts', prudentes, and Christians were 'stupid'." And so Augustine churned out a Juggernaut of literary allusions and "cumulus clouds of erudition." He paid special attention to aligning Christianity with Greek philosophy and Platonism in particular (with Christianity, naturally, portrayed as building on and far surpassing what had come before). In terms of impact, Augustine succeeded so well that his distorted Christianizing "analysis" of Pagan philosophers from Plato and Aristotle to Plotinus and Porphyry is still strangely influential among scholars of late antique philosophy.
Augustine's City of God, then, is yet another example of the need for Christianity to explain itself in the same basic way that religions had always explained themselves. Christians sought to claim a continuity with the past, in the same way that previously introduced religious innovations had claimed such continuity. The rather obvious difference being that where all previous examples of this phenomenon had merely added a new wrinkle to the richly textured fabric of religious diversity, the Christians undertook the extirpation of all other (that is, all previous) religious traditions whatsoever, while still claiming continuity with the past.
