[starman2003]

When the Roman Emperor Julian the Apostate became Emperor, he "persecuted" Christianity by banning Christians…….. This was so hurtful to Christians in terms of revenue and prestige that they arranged for his murder.

Julian was fatally wounded by a projectile during a counterattack he led against Persian forces. Of course there were bound to be rumors that a christian soldier in his army did it, but that's not most parsimonious.

[Rich]

If Christianity had not spread successfully in the Roman Empire and Constantine had not converted to Christianity in the fourth century is it possible that Islam could have spread in its place?

Apologies but this is an absurd question. It reminds me of questions like if the Union had lost the ACW would Germany still have lost the first world war as if everything else would just carry on the same. If the Union had lost the ACW there would have been no first world war, at least the war we know. Yes there might have been a big war between Germany, some allies against some other other major powers but it would have been a different war at a different time, fought over different casus belli and almost certainly with not exactly the same participants.

We can be absolutely certain that Islam would not have spread, because we can be absolutely that Islam would not have existed. We can be absolutely certain that Mohammed wouldn't have existed. Now its possible that Muhammad never existed in actual history, but that wouldn't matter because none of the other people who created and spread Islam would have existed either.

Why are the scientists so stupid? They say things like the problem with time travel is what if you went back and killed your killed your great grand father before he had had children. As if that was the limit of the problem. If you could go back in a time machine to 1900 and move a single molecule on Pluto, not a single human alive today would now exist because conception is a chaotic process. And even if you say I want to be able to magically fix the conception issue, conception itself is predicated on a numerous other chaotic systems. History is numerous entangled chaotic systems. Even if you try and exclude the human individuals as historical subjects, war and other social processes are also chaotic. Unless you believe in divine / simulation-programmer intervention then the the appearance and spread of Islam was a massively, massively contingent event.

If Christianity had not triumphed its certainly credible to say it would have left an opening, but what crazy religion or religions and from what origins would have taken advantage of that opening I would suggest it is impossible to say.

[late]

Sorry, haven't read the thread, and I am not going to.

Religions were a dime a dozen back then. Without Rome, Christianity would likely have joined the hundreds of religions that have died.

[starman2003]

Without Rome, Christianity would likely have joined the hundreds of religions that have died.

Rome actually impeded christianity, to an extent. Armenia was the first christian country.