Jews, maybe, in Rome itself (and perhaps in Carthage, though their near-total absence from the works of Cyprian
The main problem with identifying African Jews is that we're either talking of Hellenized populations, less identifiable, or Berberized (which make them less known) but we know for certain about Jewish communauties on coastal Africa by the imperial era : trough both archeological (Gammarth's tombs, Synagog of Hammal Lif) and litterary sources (Yerosolemite Talmud, but also Roman texts).
I don't think the Jewish presence in Africa and Mauretania (both coastal, but also deeper, as hinter by the Judaised Berber tribes in Late Anqituity) is debated now (at the contrary of their origin : how much native element, and how much came from Italy or Spain, especially in Late Antiquity for the latter).
It's not really much of a regional specificity, you have a relatively important presence in coastal Spain and southern Gaul.
But Manichaeans? In the early fourth century? What evidence do you have for that?
The main problem with Manicheans is that we're tributary from polemical texts, as with Augustine, and that archeologically the difference with paleo-Christian communauties is hard to do.
That said, we know it was present in Africa at roughly the same time than Christianity : the presence of an egyptian "bishop", Addas, in the IIIrd century or, of course,
Diocletian's anti-manichean edict being due to Julianus ,then Africa's proconsul, being worried about the development of Mani's followers in his province.
We're not talking of some converts, but of an organized (possibly with important ties with Egypt) communauties.
And how much does rural Christianisation matter? The bulk of the empire was always rural, of course, but nearly all of its sophisticated culture, governance, etc. went on in cities.
It began to change with the IIIrd century and the IVth : municipal power began to wane in the western provinces (even if it's less the case for pronconsular Africa and most of Italy) at the benefit of semi-rural centers.
It's why really secondary cities in the West you'd struggle hard to find mention in earlier centuries, became seat of bishopries in the IVth/Vth centuries : it means that even if relatively superficial by the beginning of the IVth century, Christianity became an unavoidable institution into territorial and social organisation.
Not that the absence of strong semi-rural or rual presence is an hindrance to Christianity development, but it certainly prevent Africa playing the role that Oriens did, where you had the aforementioned presence by itself.
Christianisation in the East wasn't just on metropolis and urban centers, and that makes a huge difference.
They aren't just going to go away, and they are likely to have some effect.
Possibly, but at this point, Christianity is anything but really formed and well defined : more open to outer influences and without the structuring help of imperial power, you'd end with a mosaic of small communities with their own doctrinal and pastoral conceptions.
Eventually, it could go either as Judaism did in western Late Antiquity, or being absorbed as Manicheism was.
The reality was more complicated, as you recognise in discussing the Franks (I hadn't realised that there were Jewish converts among them; do you now what the reference for that is? I would be very interested to look it up); the barbarians developed their own approaches to Christianity which existed in a real relationship to Roman Christianity, but did not assimilate them straightforwardly into Roman culture or government or anything else.
Actually, they did get assimilated into Roman culture or governemental structure from the start : their ethnogenesis was entierly due to Roman influence and meddling. Franks, for instance, wouldn't have existed as such if Rome wouldn't have created a series of laeti and foederati status to "fix" what was basically a league of peoples.
On this regard, Barbarian approach to Christianity eventually joined up with Roman approach, while from a different standpoint : both saw the necessity to distinguish populations that were extremely close, and both strived about a similar religious policy (as it was
underlined by Bruno Dumézil)
A different, early, approach of Christianity (which, again, they didn't developed but rather "received" and eventually kept as identitarian feature) doesn't mean a different religious approach for Barbarians.
As for Franks, it's admittedly hard to have one source : it's more a case of not that differentiated religious differences, and known cohabitation of various religions (see Council of Vannes) : in spite of the likely superficiality, you have some exemples up to Carolingian era as with
Bodo's conversion.
Basically, the recurent mention of "Judaising" errors by the Councils of Orléans points to a possible Judaic transmission parallel (not really outside, of course) to traditional communauties, among Franks (which were less "ethnics"* Franks that Gallo-Roman population quickly identifying as such).
Admittedly, I should have said "Judaised" Franks rather than Jewish.
*If we can use the word "ethnic" for a mix-up of various Germanic and Roman elements.
Take, for example, the Vandal persecutions of Nicene Christians in Africa: famously, Huneric and other Vandal kings mimicked Roman repression of adherents of their own 'Arian' doctrine, but turned it against 'Catholic' homoousian Christians.
There was a lot of exaggeration on this regard, tough, essentially from Victor of Vita.
Not only the troubles mostly touched the episcopal institution, rather than the clerical institutions as a whole (it's not clear if there was a double hierarchy as it existed with Visigoths or not). Was it bad politics from Huneric? Possibly.
That said, contrary to the attempts of, say, Alaric II to pull a compromise synod that could have worked thanks to (and because of) episcopalian structures forming the bulk of post-imperial Romanity cities; it wasn't this much the case in Africa : it doesn't seem Africano-Roman aristocracy much minded these religious issues until it backfired and that Berber swallowed up the kingdom.
You could be a Christian, you could even exercise religious policy in the Roman style, and still be neither Roman nor an adherent of the kind of Christianity advocated by the Roman government.
Romanized doesn't mean being Roman, as much as Americanized doesn't mean being American.
I don't think anyone claimed the contrary on this thread : Roman and Barbarian, in spite participating to the same Late Roman structure remained two distinct political identities.
we simply cannot know that barbarians would not have become converted independently of imperial support.
I agree even more that I stress the contrary : romanisation and christianisation weren't always a matter of imperial initiative. I gave earlier the exemples of Burgondians switching from Nicean to Homean beliefs (or rather their leading aristocracy) because it was more convenient for identitarian and political purposes. And that wasn't certainly imposed by Ravenna.
My whole point is : as Christianity became a key feature of Roman institutions and culture, regardless the (sometimes really minor to anyone but theologians and imperial factions) difference; and giving that Barbarians themselves were going trough an important romanisation as they entered in Romania (or even at its margins), one wouldn't likely go without the other.
Without Christianity, you'd certainly have something roughly similar, with or without imperial intervention but benefiting from institutional prestige, as some sort of equivalent to IIIrd century's
Mars Thingsus. I think we're agreeing there.
I would agree, except that we cannot ignore his many letters to priests. 'Structured paganism'? Maybe not, but he really did want to change the appearance of 'paganism' on the ground.
Was it more changing the appearance of paganism, than attempting to make anti-Christian elites or elites that prided themselves from tradition to simply be more credible, theologically and culturally?
For instance, I can't remember the name of this Roman noble that, at the end of the Empire, collectioning almost all traditional religious high titles, joking about how, if he could be pope, he would convert to Christianity.
"Paganism" seem to have suffered from a huge credibility crisis at this point, at least among urban population, and I wonder if Julian didn't tried to resolve that with a philosophical answer to philosophical dismemberment of traditional beliefs.
But can't we be more specific than that? It isn't simply a matter of the emperor deciding; it is (I suspect) a matter of the emperor's advocating a kind of earnest, more philosophical, frankly more 'serious' kind of paganism than the local people wanted.
Possibly, but I suspect myself that it's more a mistake due to the incestuous relationship between personal beliefs of the emperor and imperial religious policy in the IVth.
Julian seemed honestly confused by the ruckus he caused, less (in my opinion but I should check myself the sources) because he actively wanted to modify traditional rites to purify them, but because he didn't saw the relation between openly expressing a more philosophical minded approach of religion (that existed at least since the Ist century) and how it would influence on the religious policies of the empire.
He would have been right if he would have ruled during the Ist or IInd century (with each emperor having his domestic philosopher, and quasi-gnostic take on traditional beliefs, but after almost one century of institutionalizing Imperial cult, it couldn't hold.
That said, we may have to agree to disagree on this.
Perhaps my assertion of 'incompetence' goes too far, but I think Julian failed as a politician--he just wasn't good at winning over the bulk of the urban population
I think we can agree on that.
Like, rather than an Emperor converting, the Roman Empire just allows Christianity as one of many faiths but places limits on it and continues to promote the official pantheon as the religion of political power.
Very roughly, it's not impossible to have such happening (and you had several occurrences of emperors having a belief much different than traditional civic cults), but it doesn't seem particularly likely to last with the growingly personal and charismatic imperial figure (admittedly, it accompanied the imperial cult importance rather than causing it).
Religion played an important role for imperium, the lesser not being political legitimacy and military one (whatever Mithra, Sol Invictus or Christ, it allowed giving an
esprit de corps to imperial troops).
As Calaritanus pointed, it was dependent as well from personal (and factional) politics more than deep down belief (let's be clear : it did played a role, but we can see that Constantine himself hesitated a lot before choosing Christianity).
Eventually, you'd have someone pulling an
In hoc signo vinces in behalf of a spiritual figure relevant enough to their political and spiritual needs. Doesn't mean it had to be something monotheist : Sol Invictus or Mithra didn't challenged the civic, traditional or personal cults as Asclepsios (this one was immensely popular).
I think it would quickly go down to two holistic or even monist beliefs, rather than traditional vs. Christian.