In this alternative reality Constantine the Great never embraces the Christianity and the Roman Empire remains polytheistic.

So I would like to know what realistic change(s) could have prevented the spread of Christianity in the Roman Empire ?

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    $\begingroup$ If Nero couldn't stamp out Christianity, it's hard to conceive of a realistic situation short of it never happening. $\endgroup$
    – JBH
    Aug 11, 2018 at 20:49
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    $\begingroup$ @JBH Nero was but a god-emperor.. $\endgroup$
    – dot_Sp0T
    Aug 11, 2018 at 21:10
  • $\begingroup$ @dot_Sp0T, he certainly thought himself one. $\endgroup$
    – JBH
    Aug 11, 2018 at 21:23
  • $\begingroup$ COMPETITION BETWEEN EXCLUSIVE FAITHS: WHY THE JEWS CEASED PROSELYTIZING Mario Ferrero. $\endgroup$ Aug 12, 2018 at 1:28
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    $\begingroup$ @KeithMcClary did you had to shout tho..? Also the paper says 'First draft... do not quote...' - do you have a source that is officially quotable? $\endgroup$
    – dot_Sp0T
    Aug 13, 2018 at 7:50

10 Answers 10


I think that Constantine the Great was just the last drop in the already filled vase. Changing his decision would have little or no effect on the spreading of Christianity in the Roman Empire.

First of all, Roman religion was intrinsically open to external influences: there are several accounts of foreign gods which were, more or less, accepted or tolerated in the Roman Pantheon or religious behavior. When Christianity started to spread, it was just one among the others.

Moreover, around the 3rd century A.D. the old corpus of the Roman religion, with its values and traditions, was already showing crisis signs: internecine wars were common in the empire, barbarians were already pressing the empire's borders and the economic crisis was hitting the empire.

No wonder that there was lack of trust in the old gods, which were showing more and more how they were no longer able to ensure prosperity and safety to the empire worshiping them.

If you really want to prevent or reduce the spread of Christianity in your world, I think you have to work on those factors I have listed before:

  • openness of the religion: make the Roman religion much more closed and afraid of accepting foreign cults
  • internecine wars: reduce them, make the central government strong and respected
  • barbarians at the border: again, make the central government strong, so that the army is efficient and used for protecting the borders, not for supporting generals fighting for their seat in Rome
  • economic crisis: I have no knowledge here to hint at what could be done, if I had I was working in ECB right now.

All in all, I think you are more or less trying to avoid that fruit flies gather around a ripe peach.

  • $\begingroup$ Perhaps also increase the openness & publicity of Mithraism. It was already widespread within the military. $\endgroup$
    – elemtilas
    Aug 11, 2018 at 12:28
  • $\begingroup$ @elemtilas Didn't Mithraism already contributed as one of the major bridges from Roman polytheism to adopting Christianity? As I recall there was a lot of "blending" onto Christianity, which made it much more acceptable to Roman soldiers in the end. $\endgroup$
    – Upper_Case
    Aug 11, 2018 at 16:07
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    $\begingroup$ A little fiddling, and you could have a charismatic barbarian leader make a go at converting the Romans to a form of paganism. That's not technically Roman polytheism, but it sure isn't Christianity. $\endgroup$
    – Cadence
    Aug 11, 2018 at 19:12
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    $\begingroup$ +1 for pointing out that Constantine was but a single note in the symphony that is the Roman history of Christianity. $\endgroup$
    – JBH
    Aug 11, 2018 at 20:52
  • $\begingroup$ I think one way to reduce Roman tolerance would be to keep their pantheon relatively small. It's much easier to smuggle a new god (and then build up your religion around him) when most people don't even know half of their original pantheon. $\endgroup$
    – Nolonar
    Aug 11, 2018 at 20:57

If you don’t want Jesus to just never have existed, then I’d suggest that the minimal change would be for Saint Paul to not have his vision on the road to Damascus, which would likely keep Christianity as a small Jewish sect.

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    $\begingroup$ I think Paul was more politically motivated than driven by divine vision (which he may or may not have invented to bolster his claims) but i agree that Paul is probably a good point of influence. $\endgroup$ Aug 11, 2018 at 11:47
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    $\begingroup$ @KonradRudolph : politically motivated? Come on, how could someone be politically motivated to give up a position of power and join a (then) heavily oppressed group and risk persecution? Such a conversion is unlikely to happen without strong personal conviction and strong belief. No one switches from the winning side to the (at the moment) losing side for personal political gain. But it's true that Paul helped a lot in having Christianity spread outside of the Jewish community. But that happened later, after he traveled a lot and established churches all around the empire. $\endgroup$
    – vsz
    Aug 12, 2018 at 9:06
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    $\begingroup$ @vsz shrug lots of potential reasons, but I didn’t say that they wouldn’t require strong personal conviction. I’m just saying that reasons that don’t involve divine visions are, historically speaking, quite a lot more likely than reasons that do. And that’s even if you’re religious. For non-religious people it’s even more one-sided since the chance of divine visions is exactly 0. $\endgroup$ Aug 13, 2018 at 8:49
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    $\begingroup$ @KonradRudolph : It's not even about the miracles. You claimed that his actions were not driven by his beliefs, but by his political calculations. Which is absurd. Had the New Testament been a political propaganda, it would have shown the Apostles in the best possible light. But instead is shows their mistakes, their failures, their doubts. Everything strongly indicates they really believed what they were preaching, and risked their lives for what they believed. They couldn't have gotten any worldly benefits, and there were some who gave up positions of power to do what they believed was right $\endgroup$
    – vsz
    Aug 13, 2018 at 14:40
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    $\begingroup$ @KonradRudolph : Well, than this brings us nowhere, because one could say the same about historians arguing that the apostles were only motivated by political gain, to be writing purely carefully-crafted propaganda. $\endgroup$
    – vsz
    Aug 13, 2018 at 18:18

With or without Constantine, by the early 4th century Christianity was one of the two most popular religions in the Roman empire. Constantine adopted Christian symbols exactly because it was already popular.

  • In this alternative reality Constantine the Great never embraces the Christianity...

    ... and loses the civil war.

    The situation was that the Roman empire was, officially and in principle, a tetrarchy, with Constantine as (irregular and contested) Augustus of the West, Maxentius as Augustus of Italy, and Licinius ruling the rich and stable East.

    By 308 CE the political situation decayed into a six-sided civil war; Constantine had the allegiance of the legions of Britannia, Gallia and Hispania, relatively poor provinces, whereas his principal opponent, Maxentius, controlled Italy.

    Constantine needed a simple and clear differentiator, so that people could easily understand what Constantine stood for; in a stroke of genius he adopted the banner of the monogram ☧ (Chi Rho, for Christos), thus signalling his position as emperor of the people fighting against the political establishment. He won the war under the Christian banner, and that was that.

    (While the other competitors used standard traditional political imagery, Constantine adopted a symbol of the religion practiced in various ways by about two thirds of the population, especially the lower classes. By placing the symbol on his banners he implicitly made a promise to elevate the religion of the masses to equal status with the established state religions.)

    Chi Rho monogram

    In hoc signo vinces (under this symbol you shall win); public domain image by Dylan Lake representing the character U+2627. Available on Wikimedia.

    After the civil war was over, Constantine (now the uncontested Augustus of the West) and Licinius (Augustus of the East) signed together the Edict of Milan which recognized Christianity as an accepted religion in the empire.

  • ....the Roman Empire remains polytheistic.

    By the early 4th century AD the traditional Roman and Greek religions were on life support; basically nobody practiced them any longer except as required by state ceremonies. They did remain in use as a source of literary and artistic tropes and subjects; but this is not life. Consider that in 2018 AD, Hollywood made a commercially successful movie where one of the main characters is a strong supernatural person named Thor, who wields a magical war hammer, claims to come from Asgard, and to be the son of Odin: this doesn't mean that the old Germanic religion is alive.

    Among the urban lower classes and in the army the most popular religions were Christianity (of many various sorts) and Mithraism. Polytheism remained strong only in the countryside; consider that the English word "pagan" comes from Latin paganus, which properly means villager.

  • So I would like to know what realistic change(s) could have prevented the spread of Christianity in the Roman Empire?

    Don't focus on Constantine; it is way too late. By the early 4th century the only question is whether the empire will be Christian, Mithraic, or maybe both. The traditional polytheistic religions of Rome, Greece, Gaul, Britain and so on were effectively dead by that time.

    As for the question as asked, what changes to make in order to prevent the spread of Christianity, the answer is simple and well-known. Kill Paul, or at least give him a strong incentive to forego transforming a marginal Hebrew sect into an attractive universal religion. Without Paul, Christians are ordinary Hebrews, one of the many sects into which Judaism splintered after the destruction of the Second Temple.

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    $\begingroup$ Thanks, I was not aware of this. It is even more surprising to me that Diocletian persecuted Christians in the beginning of the 4th century en.wikipedia.org/wiki/Diocletian#Great_Persecution . But apparently it was for political motivations. $\endgroup$
    – user53220
    Aug 11, 2018 at 19:37
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    $\begingroup$ @user53220: Diocletian was the closest thing to a political genius the late empire produced. Alas, he fell far short of his goal of saving the empire. He issued several edicts against Christians, which were by and large ignored by the population. He introduced the tetrarchy as a solution to the problem of governing a very large and very diverese empire; it decayed into the mother of civil wars within his lifetime. He issued an Edict on Maximum Prices which destroyed what little remained of the economy of the western half of the empire. $\endgroup$
    – AlexP
    Aug 11, 2018 at 20:05
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    $\begingroup$ @AlexP If Diocletian issued edicts that were ignored, laid the foundations for a massive civil war, and destroyed the economy, then what exactly makes him a “political genius”? $\endgroup$
    – Mike Scott
    Aug 12, 2018 at 6:28
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    $\begingroup$ @MikeScott: He recognized that the empire had a structural problem, he diagnosed it correctly, and he offered a novel solution. His solution didn't work, but it might have worked, at least for a time; but it was not to be. Contrast with Constantine, who saw the same problems, decided they were intractable, and simply partitioned the empire into a "good" eastern half and a "bad" western half; this allowed the eastern half to survive for a thousand years, but condemned the western half to the long night of the middle ages. $\endgroup$
    – AlexP
    Aug 12, 2018 at 12:33
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    $\begingroup$ I just noticed that AlexP is Ale + ☧ ! $\endgroup$
    – user53220
    Aug 13, 2018 at 13:15

This is a deeply controversial topic by virtue of the fact that it touches on many belief systems to a point where the known history is hotly debated where it doesn't necessarily agree with established dogma, especially Catholicism. The official Catholic position is that St Peter formed the first united (or catholic) Christian chruch, and that he was its first pope.

Contemporary history indicates that the first leader of any church that we would recognise as Christian was formed by Constantine, and that Christianity after Constantine bore little to no resemblance to Christianity before him.

One could argue that this was because it was deeply fragmented due to ubiquitous persecution and therefore Constantine represented the first opportunity it had seen in centuries to form around a coherent declaration of faith and practice, but the bible that was agreed to as Canon during his time contained far fewer gnostic (mystic) texts than agnostic (non-mystic) texts (the most notable exceptions to this being the gospel of John and his book of the Revelation).

The point being, there is a historical argument that Constantine didn't spread Christianity, rather he spread a religion that he created in an attempt to unite the Roman Empire under a single faith, and just hijacked the name Christianity because it was lying around everywhere (meaning he wouldn't have to explain where a brand new religion just came from).

Let's (for the sake of this essay) assume that this is the most historically accurate interpretation of what occurred.

If that was the case, he did it because he was now in charge of a massive empire of deeply divided faiths, cultures, and systems of administration. The Romans were adept at propaganda and their secular structures of government were already compelling, so converting people across the empire to a Roman culture and form of government was the easy bit. But, people get very particular about their gods and just telling people that the Roman pantheon of gods were 'the real gods' was never going to work, and Constantine knew that. He needed something new, in which all people could see aspects of their original faith so that he could sell it as a refinement; a new Roman way of seeing religion, if you will.

At this point in time, the only truly ubiquitous religion in the Roman Empire was Christianity, but it served as an underground pariah to all other faiths. This, at the very least, meant all knew of the name of Christianity, even if they didn't know their dogma. At this point in time, they couldn't have anyway because the religion was so decentralised, and worked from many disparate sacred texts.

But Constantine doesn't want the dogma; he has his own ideas for that. He just needs the name. Most Christians don't mind this so much. Their god and their messiah get an upgrade, they're not hiding from people wanting to turn them into catfood (feeding them to lions) and they're sick of fighting among themselves as to what it means to be Christian anyway.

Now for the real trick; introducing all the other elements that allow for people to see their own original faith.

Ironically, the easiest is polytheism. Instead of a God of this, God of that, you now have a Saint of this, Saint of that. Move the day of Christ's birth to the date of the Winter Solstice (or the Roman Saturnalia) because most other faiths consider that date significant, change the day of the Sabbath from the seventh day of the week (Saturday) to the first (Sunday) because it fits in better with other religions that dedicate the first day of the week to their other Gods...

The list goes on.

But why would he do this? For the same reason that the British Empire struggled in India; different religions introduce different holy days, religious practices, clean stuff, unclean stuff... You just can't get anything done unless you have everyone singing from the same hymnbook. Constantine knew that the best way to motivate and unite an army drawn from every corner of the Empire was to have them unite under a single faith, and that's easier under a single god.

So IF (and it's a BIG if; I'm not saying for a moment any of this is fact, it's just a single interpretation of events for the purposes of providing an answer) you don't want Constantine to do this, you have to give him other options.

Here's a few;

1) Don't make the Roman Empire so successful
If the Romans aren't taking over cultures left, right and centre, there's no need to unite the people. A slower rate of expansion means a slower rate of assimilation, which means people are more likely to be of a Roman faith by the time the next group are being conquered. Slower expansion and less success means no need for Constantine to unite under a single religion not Roman. Also, a less successful Roman Empire probably doesn't make it into the Middle East in the first place; problem solved.

2) Have a ubiquitous European polytheistic faith already
If all of Europe believed what the Romans did (or something similar at least), then you have no need to create something new. Most Roman gods bore a strong resemblance to Greek gods anyway; if the Greeks had been more successful in propagating their own religion before the Romans come along, Christianity doesn't get a look in.

3) Organise Christianity early
Arguably, very early Christians were hampered by a pacifistic stance to persecution. Their God was going to give them their reward for sacrifice and boldness in spreading the word, not for striking back against those who attack them. Change that single doctrine about turning the other cheek, make Jesus somewhat more Old Testament in his approach, and Constantine can't take the name of Christianity and subvert it because he's too busy fighting them as his single biggest threat inside the territory of the Empire.

4) Make Romans (All Romans, including conquered people) xenophobic
If the Romans were so convinced of the rightness of their cause, and were adept at assimilating the conquered nations into accepting that belief right off the bat, Constantine (again) can't use Christianity the way he did. You'd have a civil war on your hands right off the bat. In point of fact, by the time Constantine gets into power, the Roman Empire is suffering from all sorts of growing pains beyond Roman technology to fix and Romans are starting to wonder about their Gods as it is, what with Barbarian invasions, economic issues, etc.

Put simply, Christianity was an idea (arguably Constantine's idea) whose time had come and it was either the second chapter of God's will on Earth after his Son, or the largest social engineering experiment ever conducted on this planet. It's entirely up to you which you believe, but this essay (hopefully) goes some way to explaining what some of the possibilities were at the time.

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    $\begingroup$ A number of errors here. Peter didn't form the Church; Jesus did and made Peter the first pope. The Church after Constantine was really no different than the Church before, except that it gained in political clout. I'm wondering what kind of uninformed historian would not recognise the three centuries of the Church's existence and activity before Constantine. Until the 11th century, the Church really was, in every sense of the word, unified. There were, of course, heretical groups that were dealt with, but literally, from Britain to North Africa, to Arabia and up into Armenia, one Church. $\endgroup$
    – elemtilas
    Aug 11, 2018 at 12:34
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    $\begingroup$ @elemtilas And you're doing what Tim explicitly mentioned in his first paragraph. The pre-Constantine church was not centrally organized, which is why we have all those Epistles from self-proclaimed leaders to tell other groups how they're supposedly getting it wrong, and why the Council of Nicea was necessary to settle on a unified message of what did and didn't constitute Christianity. $\endgroup$
    – Graham
    Aug 11, 2018 at 12:59
  • $\begingroup$ And all those Epistles were carefully preserved by the other groups. $\endgroup$
    – Mary
    Dec 20, 2022 at 3:27
  • $\begingroup$ @Graham While I don't buy every part of what elemtilas is saying, there was an organised church before Constantine. Justin Martyr describes various consensus and controversial beliefs by 160 AD and other early texts support it; furthermore, the role of bishops (whether 'monarchial' or not) is attested to by almost every early Christian writer. Polycarp, Eusebius, Clement, Justin Martyr, and many others were or attest to the role of bishops in some form of organised structure, the details of which are contested by Catholics, E.O's, Protestants, and atheists. $\endgroup$
    – user86462
    Dec 20, 2022 at 3:30

Starting with Constantine might be way late. You’ve got to nip it in the bud, which would be Paul.

That 13 books of the New Testament were attributed to him should show how much influence he had in early Christianity. Before him, it was just another apocalyptic Jewish sect. Paul not only worked to include gentiles (non-Jews) in the new faith, vastly expanding the population of possible converts outside Judea, but also personally established churches across the Empire.

Removing Paul is the single most destructive action you could take. And it wouldn’t even be that far a stretch. He was a Pharisee who had never met Jesus and actively persecuted Christians before he converted.

Another tact you might consider would be to avoid the destruction of the Second Temple in 70CE. Foretold by Jesus, the destruction gave creedence to Christianity and weakened traditional Judaism, which had centered around sacrifice in the Temple. Interestingly, the emperor Julian (the Apostate, r. 361-363), Constantine’s nephew and staunch polytheist, attempted to rebuild the Temple to undermine Christianity’s growing influence.

A further area of interest is that while Christianity - monotheist in the land of polytheism - was an illegal religion in Rome, Judaism itself was a legal cult. This is because their sacrifices in the Temple were considered sacrifices to Jupiter. Rome was fine with whatever faith you had if only you offered a public sacrifice to keep the gods off everyone’s backs.

Christianity was banned because they refused to sacrifice to the state deities. In many cases, the punishment for being a Christian came only when they refused to offer public sacrifice. That led to martyrdoms and people do love a good martyr. A loosening of restrictions might have contribute to Christianity becomeing just ‘one of the weird cults’ in the empire, not the resident neighbor-loving bad-boys who got so popular for sticking it to the man.

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    $\begingroup$ This is actually a good answer (welcome to Worldbuilding, btw) however I'm not convinced that you can measure the influence of a pre-Constantine advocate of Christianity by the percentage of their work included in the Bible. Constantine was very much against the more Gnostic texts for instance, even if they had been influential to others. Also, Indian Christianity prior to European contact being more common was almost exclusively based on the Book of Thomas, which doesn't even get a look-in with Constantine, probably because it wasn't well known in Europe, if at all. $\endgroup$
    – Tim B II
    Aug 13, 2018 at 7:24
  • $\begingroup$ The interssting thing about the number of books in his name is not that they were all written by him, but that a number were not (somewhere around 6 weren’t). That suggests that his name was influential enough to copy. But, yes, that in itself is not an indicator of how important he was. It is his abandonment of the food laws that I think makes him an invaluable cog in Christianity’s evolution, especially in this question. Including the non-Jews exponentially expands Christianity’s sights in the empire. Jews were a insignificant minority (in raw numbers) most places outside Judea. $\endgroup$
    – JoseHood
    Aug 13, 2018 at 7:38
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    $\begingroup$ You shouldn't remove Paul... just he should remain, with all his talent and hard work on the opposing side. $\endgroup$
    – Shadow1024
    Aug 13, 2018 at 8:48

Make Pontius Pilate let Jesus go. Jesus's whole movement depends on his persecution and violent death. If that never comes, his cult dies with him; peacefully in his sleep in his late 60's.


Have the tribe of Israel wiped out during the bronze age collapse. In those days they were just an insignificant mountain tribe in the Egyptian province of Canaan. During the chaos of the collaps they might run into an army attampting to kerp the order up or a raiding band of sea people and take a devastating defeat. The warriors are slaughtered and women and children are made slaves.

No Israelites, no Jews, no Christians and by extend no Islam. Zooastriaism reamains the only monotheistic religion and Hellenistic polytheism stays state religion due to the lack of a popular alternative.

I don't think that this will butterfly effect Rome out of existance and it would also prevent the Jewish revolt as a nice side effect, further stabilising the empire.


1) Modernize the roman faith

as mentioned by @Mark_Olson even near the end of the empire there were many attempts to revitalize Hellenism most notable with Julian who tried to undermine Christianity through intellectual means and tried to create a more unified roman religion

He would primarily attack Christianity in his writings, leveraging the debating skills he had gained from his education. In one of his works, the Caesars, Julian attacks Jesus for preaching forgiveness. He effectively argues that Christianity attracts people who have no interest in self-improvement but want to be absolved from all their wrongdoings. In his Against the Galileans on the other hand, he attacked Christian dogma as unrealistic and superstitious.

Julian got a friend and philosopher, Sallustius, to write a catechism outlining a new pagan belief system for his new church to use. Sallustius’ document is extremely interesting and favors a philosophical and non-literal interpretation of pagan myths. Philosophy and religion had to be brought together to create a serious competitor to Christian dogma. Julian’s brand of philosophy was a form of Neoplatonism, a school of thought which attempted to reconcile competing philosophical traditions into one god-given series of revelations. Ideas found in Plato were applied heavily to pagan religions


simply having a Julian type emperor early around say the 1st or early 2nd century, who understood the threat the new religion and tried to combat it by making Hellenism a more unified religion as well as making it more appealing to commonfolk (a centralized set of main gods, downplaying the negative aspects of the gods, promising that normal people can enter Elysian Fields through devotion to gods and strong morals, ect...).

would it be like classical Hellenism no but this new brand of Hellenism has a much better chance of surviving, plus assuming the romans aren't as driven to convert neighboring territories as Christians in our timeline you could easily see many other pagan religions surviving in their original form which does have a lot of story possibilities.

2) Don't persecute Christians

One of the main ways Early Christianity was able to spread so quickly was the martyrdom of many of it's believers (hell the entire religion started because of the martyrdom of jesus).

technically Christianity wasn't illegal in the roman empire just like how Judaism wasn't, the main reason why Christians were persecuted was due do their refusal to take part in sacrifices. simply make it so sacrifices aren't mandatory or replace animal sacrifices with more abstract personal sacrifices (something that also makes this new brand of Hellenism more appealing) and without the martyrdom aspect Christianity would be regarded as just a weird sect of Judaism to a large portion of the population

3) Have the late empire be more stable

another thing that lead to the spread of Christianity was the instability of the Roman empire, from constant barbarian raids, to a weak and ineffective government lead many people to become disillusioned with the old gods and turned to Christianity. a stronger more respected government that's able to hold off barbarian attacks and putting most of this success to the strength of the old gods, would reduce this. as an added benefit the western roman empire would last longer than in our timeline.

4) Profit

what you're left with is a more stable roman empire with a strong centralized pagan faith with small but tolerated Christian communities throughout, contrasted with the more traditional and disorganized faiths further north.

it's entirely possibly for religions like Christianity and later Islam to still become popular in places like North Africa and the Middle East though they'd have a difficult time propagating into Europe especially as roman ideas of organized religion would slowly spread up north.


The Assyrians went full on genocide and wiped out the Jewish people.

No more Judaism let alone Christianity.


I make no claim about realism and leave that for the reader to judge.

I will comment in advance that my answer depends upon what some people may consider to be a minor detail of Christianity: in the New Testament, there is allegedly eyewitness testimony of Jesus raising Lazarus from the dead.

Now, we are prepared for the change(s):

Change general public opinion in ancient Israel and general public opinion in the Roman Empire so that people agree that raising somebody from the dead without prior, written authorization from the local government authorities warrants an official government response:

Specific Performance: the convict is required to raise from the dead at least a dozen, prior influential individuals such as Zoroaster and the Buddha. One foreseeable result is a more competitive environment for religious leaders, making it more difficult for people who preach Christianity to dominate in the marketplace for religions.

An alternative change (again, it is for the reader to judge realism): provide the Roman Empire with a constitution forbidding Roman legislators from establishing an official religion. Thus, Christianity could spread, but not via the big stick of government authority, unless the constitution were first amended to permit an official religion.


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