User blog comment:LurkerLordB/Religion in a world without Christianity/@comment-1310192-20120423015548

Roman and Greek polytheism would rule in the west of Europe as well as most of North Africa. In Egypt some sort of Graeco-Egyptian polytheism would still exist. In the east, Zoroastrianism could displace the Semitic religions, or coexist with them a la they did with Nestorianism, while Persia would be very Zoroastrian.

If "Islam" was ever to break out, it would be a dualistic religion akin to Zoroastrianism.

It is possible the Roman Empire declines later on although it will likely decline at some point anyways. Sassanid Persia and a Byzantine Empire would likely be the world "mediaeval" powers.

The world might be better off since the Greek works would never be thrown away because of their "paganism"; it, however, might also be worse off because of no unifying force in the west. Definitely a Zoroastrian Persia would be more advanced than a Polytheist West IMO.

Quite an interesting scenario really.