Quite by accident I encountered a paper by Andrew Fear in a Festschrift, entitled “Cybele and Christ.” In this article, he makes the interesting suggestion that late paganism started to adopt various features from Christianity. His examples are the cult of Cybele, but probably the trend would be equally visible elsewhere.
There is the well known statement in the Historia Augusta  that Alexander Severus had a shrine in which he had statues of Moses, Orpheus, Apollonius of Tyana, and Jesus, alongside his ancestors. This text is now known to be fourth century. Indeed such an attitude towards Jesus is difficult to imagine in the second century, and not that easy in the early third century. Jesus was a disreputable figure in that period, as the accusations of Celsus in Origen’s Contra Celsum, or of Caecilian — possibly copied from Fronto — in Minucius Felix’ Octavian make clear.
In the early fourth century, the idea of the sage was present to all. In Eusebius’ Contra Hieroclem, we find discussion of the cult of Apollonius of Tyana, whom Hierocles had remanufactured as a pagan Jesus as part of the Great Persecution in the reign of Diocletian in the late third century. Eusebius attacks this; but he makes the interesting statement that he would otherwise treat Apollonius as a sage, someone of wisdom and knowledge, advocating virtue, and in a way laying the groundwork for the Christian gospel. In all this we see the germ of the later Byzantine habit of treating pagan philosophers rather like Jewish prophets, both predicting the coming of Christ; although the collections of sayings of the philosophers that were used to prove this all seem to be bogus!
But what of Cybele? Was the cult redesigned in the mid fourth century, to adopt certain elements of Christianity? It’s an intriguing idea. Fear refers to the “resurrection” of Attis, recorded by Firmicus Maternus ca. 350 AD, and dismissed by him as a new fabrication in response to official pressure on a discreditable cult. Julian the Apostate refers to Cybele as a virgin goddess . That description makes nonsense of the key cult myth. This may be summarised as follows.
In this, Attis is the boyfriend of Cybele. One day he goes off and shags a nymph, and his missus finds out. She drives him mad, he chops his willy off while under the influence and dies. Then she calms down and decides this wasn’t a good idea. She asks Father Zeus to resurrect Attis. Zeus, no mean shagger himself, disapproves of this adultery=castration myth, and declines. The most he will do is preserve the dead body. And there the myth ends.
The myth makes no sense if Cybele is a virgin goddess, and still less when the fertility aspects of the cult are considered. But the Christian cult of the Virgin Mary explains all — someone felt it necessary to attribute this idea to Cybele. Julian himself tries to get the pagan priesthoods to do the social work that the Christians do, to try to compete. His Hymn to the Mother of the Gods is still extant.
But the most interesting element of this is the 5th century work, the Life of Proclus by his successor Marinus, online here. Fear suggests that Proclus composed a “bible” for the cult, although the actual statement is more prosaic:
33. But if I was to enumerate all the facts of this kind, and to report the particular devotion which he held for Pan, son of Hermes, the great favors he received, and the numerous times he was, in Athens, saved by intervention of the divinity, and to relate in detail the protections and the advantages he received from the Mother of the Gods, of which he was particularly proud and happy, I would no doubt seem chattering vainly, to those who may light on this book by chance, and some may even think I am saying things little worthy of belief. For there were a considerable number of episodes, that were of almost daily occurrence, when this goddess [Cybele] spoke or acted in his favor; and their number and character are so unusual that I myself do not have their exact and precise memory.
If anyone desires to know with what favor he was attached to this goddess, let him read Proclus’s book on the Mother of the Gods, and it will be seen that with inspiration from on high he has been able to expound the whole theology relative to the goddess, and to explain philosophically all that the liturgical actions and the oral instructions mythically teach us about the goddess, and Attis, so that they will no longer be troubled by those seemingly absurd lamentations [for Attis] and all the secret traditions related in her ceremonies.
Certainly, however, we see the philosopher composing a tract describing a “theology”, and explaining away all the discreditable stuff about Attis and his self-castration by allegory. It is unlikely that any such effort would be felt necessary before the fourth century.
I think we could use a proper list of borrowings, from primary sources. The material given by Andrew Fear is a good start, but it is partial. Paganism was syncretic. If there was useful material to be borrowed, there was no reason not to do so. But specific evidence would be most interesting to see.
1. A. T. Fear, “Cybele and Christ” in Eugene N. Lane (ed.), Cybele, Attis and Related Cults: Essays in Memory of M. J. Vermaseren. Religions in the Greco-Roman World, 131. Leiden: E. J. Brill, 1996. Pp. vi + 441. $138. ISBN 90-04-10196-9. Mostly online here.
2. “Alexander Severus”, 29.
3. “Against the Galileans”, 262D.