This was a hypothetical statement by one of my professors.
The Byzantine Empire was one of the strangest entities of its day; for 1200 years it was a religious and cultural unity that spread far beyond its own borders, and at a couple points in time the Empire did not stretch beyond the borders of Constantinople, yet the Empire survived. So here is the theory: what if Constantinople HAD fallen during the Arab invasions of 674-8? (Or the second invasion in 717-8?)
Here is his theory (which seems sound to me, so we'll say it is my stance as well): for whatever reason, Constantinople falls in a seige. Perhaps Greek fire failed to defeat the Arab navy, or perhaps the fateful winter in 717-8 never occured. With the fall of "God's Kingdom," the last bulwark of Europe against Arab expansion falls (Carthage and Spain have already fallen/will fall shortly in 698/711 respectively). Assuming that Pseudo-Methodius was preaching allegorically and the spread of Islam wasn't actually a sign of the apocalypse, would Europe have been able to stand against the Arabs?
It's highly unlikely that anything would have happened as it did; would the Renaissance would have occured? Woukd Christianity have survived in any major capacity, or at all? Thoughts?