Druidus said:
I mean that the prosecution had continued, Christianity never being accepted as a valid religion in Rome.
Good post, frubals to you, James.
Thanks. In which case, I suggest that Christianity would still have continued to grow within the Empire as the persecutions only seem to have strengthened the faith. Every so often a slightly less vicious emperor would have come along and the Church would have been able to consolidate in the relative peace but their would have been less of a chance to call councils against heresy. This would probably have meant that the heretical sects such as the Gnostics and Arians would have existed for much longer than they did, though as some extra-Imperial states accepted Christianity very early (such as Armenia and Ethiopia), it might be that such councils would have been held outside the borders of the Empire. Obviously the importance of such states to our faith would be markedly greater than is true now.
The religion of Europe would have almost certainly been less homogeneous, though orthodox Christianity would have had a presence in all provinces from Britain to the Middle East. Other popular contemporary cults would probably have survived (such as Mithraism) but it's hard to see how such religions, which were usually popular with specific subsections of society, could have ever risen to dominance. Assuming that the political events in the life of the Empire would have stayed more or less the same, then when the western Empire fell, western Europe would have been relatively freer. Continental Europe could well have become (outside of the Empire) a stronghold of Arianism as it was very popular with the Gothic tribes. Orthodox Christianity would have dominated the Celtic lands and probably have spread into the Anglo-Saxon kingdoms solely from the north via Iona and so there'd have been no synod of Whitby and the British isles would have continued down the peculiarly idiosyncratic (though completely orthodox) way of Celtic worship. Some pagan cultures would almost certainly have survived, certainly outside of the former Imperial lands and probably in Britain.
I believe that without the Christian eastern Empire to spread and defend the faith, it would never have been so prominent in the middle east (though I doubt it would have died out) and so I would doubt that Islam would have arisen at all (no offense intended to the Muslims here). The two great powers in the East would probably have remained pagan, syncretistic Rome and predominantly Zoroastrian Persia. Zoroastrianism would probably have remained a major world religion, much more so than now.
If I go any further forward than now the speculation is just going to get wilder and wilder as the unknown possibilities just mount up. I could posit, for instance, that the religion of Zalmoxis (which had some uncanny paralels to Christianity incertain ways) would have spread out from the Carpathian-Danubian region, for instance, but there's no evidence to suggest it would. It is a (vague) possibility, though, as it only died out with the spread of Christianity north of the Empire. Who knows which would have been the most prevalent religions today? My bets would be that Christianity would survive in much the way that Judaism did with the addition of a few countries having Christianity as a state religion, but I'd guess that the major world religions would be Zoroastrianism, Buddhism (assuming my no Islam scenario) and Hinduism.
There, no miraculous interventions and all argued (so far as possible) from historical trends that I can see in the centuries after Christ. I hope that this is interesting. Do I win?
James