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The religion of Zensunnistianity has over a billion followers in the Alt-World that is otherwise identical to our Earth. Its precepts are similar to the major monotheistic religions from our world, give or take a bit of tree worship here and there. It just happens to use the ensō sign as its holy symbol, placed on ambulances and used by the red ensō humanitarian charities:

enter image description here

Now, given that there are so many followers, is it conceivable that the religion of Zensunnistianity could die out (let's define that as being reduced to fewer than a million worshipers)? Presumably, while humanity continues to exist?

Thank you for all the answers! Having read them all carefully, I am now inclined towards a negative answer to this question.

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What do you count as a follower ? All people declaring themselves followers, or people actually following the dogmas ? If it is the second, it already happened to Catholicism. Seriously, who still obey to the Pope ? Also (at least in Europe), there are way more people describing themselves as Christian, than people actually going to the church on Sunday. – Kolaru Jan 20 at 21:27
What if they have a belief that forbid say, vaccination, and then there is a new plague? – Per Alexandersson Jan 21 at 3:04
By die out do you mean that the followers of the religion die out or the concept of that religion dies out ? – Mohammad Ghazanfar Jan 21 at 6:21
@Would-be-closers, please explain how this is not on-topic for worldbuilding. Whether it is realistic to have a world a few decades removed from ours that is missing a major religion is spot-on-topic, in my view. – Serban Tanasa Jan 21 at 12:44
@Kolaru I guess by that measure catholicism never got to the 1 billion mark. – Paŭlo Ebermann Jan 22 at 19:43

13 Answers 13

up vote 2 down vote accepted

No, it’s not possible in our current cultural and geopolitic situation¹.

To reach a billion followers, a religion needs to have certain, related properties:

  1. It needs to be a “family religion”, i.e., it must be part of the religion (not necessarily its dogmata, but its culture) that followers procreate and indoctrinate their children. “Automatic” procreation is an essential evolutionary trait for species as well as religions – religions that do not have it are too unfit for survival. Acquiring followers in adulthood would not work, as people are too unlikely to switch or acquire a religion at that age. A religion without this feature would die out or be dominated by another religion before it can reach a billion followers.

  2. It must address all of society, i.e., it cannot be exclusive to a certain group of people such as a particular profession, class, age or gender. First of all, there aren’t that many groups of people that contain a billion persons to begin with. There are the genders, but being exclusive to one gender would not make you a “family religion”. There are the poor, but inevitably, some poor people will get rich and adapt the religion to allow it.

  3. It must at some time be the dominant religion in some larger area (usually a state). Nothing helps a religion prosper as good as general acceptance and social pressure. Without this, a religion can never reach a billion followers. This is also extremely helpful to wear down the edges (i.e., highly impractical dogmas) of a religion (see also the next point). As a rough estimate, half of the followers of any dominant religion only follow it due to social pressure (or such mechanisms as belief in belief) and not due to actually believing in its dogmata. This half is strong enough to shape the religion to be more feasible.

  4. It must be flexible and not entirely homogeneous. A popular religion is inevitably intertwined with culture and cannot be popular without adapting to the culture to some extent. To reach a billion followers, a religion must span several cultures and adapt to all of them. The only alternative would be no cultural homogeneity¹, which is not really possible as culture is shaped by the actual lives of people, which are not homogeneous.

    Almost all popular religions nowadays are very flexible and inhomogeneous. To address the more “difficult” examples: Many Islamic countries were much more liberal half a century ago and features flavours such as Ahmadiyya; Catholicism varies a lot over the world.

    (Sidenote: If you define the same religion so strict that this sort of flexibility is not allowed, you cannot have a religion reach one billion followers in the first place.)

  5. It must promise exclusive correctness at least to some extent; relatedly, there must be some line to draw between this religion and others. This is one of the evolutionary advantages of monotheism over classical polytheism. The promise of exclusive correctness is essential for most of the above features and is another evolutionary key factor as it keeps believers as they are less open to other religions.

    Note that I do not understand this in a way that excludes Hinduism, for example. While Hinduism is very diverse, there are still some central concepts that define it. Rather this excludes concepts such as omnism (not the discworld religion) or polytheistic religions with a very open pantheon.

Now, if there is anything like cultural mixing¹, such a religion will form diasporas all over the world (due to poperty 3), simply because adherents migrate. While this is something very prominent nowadays, it also happened historically, for example to Judaism, Zoroastrianism and Christianity – without these religions gathering that many adherents.

While some of these diasporas will die due to adopting the dominant religion or areligiousness, totalitarianism or other hostile environments, chances are high that at least some of them adapt and survive (due to properties 1, 2, 4, and 5). Some of these diasporas may manage to grow in population and sprout diasproas themselves (see, e.g., the History of Russian Jews).

Thus, even if the religion is largely eliminated in its homeland due to some reason, it is very likely that it can still accumulate a million adherents in diasporas. While it may decline in relative population, it is very unlikely to fall below your threshold of one million given the general increase of the world’s population¹.

A very good example of how (not that) this can work is Zoroastrianism, which was ironically considered a counter-example in another answer, but it never had a billion adherents (and some sources even consider it to still have a million adherents today).

To address some scenarios suggested in the other answers:

  • Celibacy – strongly violates point 1, the religion could never even remotely reach a billion followers.

  • Rituals that nurture epidemics – some diasporas will resist and the religion can adapt those rituals (point 4).

  • Explicit disproof – many religious people are comfortable with believing contradictions and then there is point 4. To give a practical example: Jehovas Witnesses survived many doomsdays.

  • Mass suicide – Won’t work due to points 1 and 4.

¹ which I consider to be part of the premise that the world is “otherwise identical to our Earth”.

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This carefully considered answer deserves far more upvotes than it has – Serban Tanasa Feb 5 at 17:16

It can absolutely die out if you give it enough time.

The most common reason a religion dies, and the only reason that consistently works is supplantation.

Take a look at some of the world's pagan religions. If we look at Greek, German, Norse and Egyptian polytheism all were replaced by monotheistic religions, namely Christianity, and later (in the case of Egypt) Islam.

These religions were supplanted through various methods. The growth of scientific thought and experimentation undercut the validity of polytheistic pantheons. Why worship Zeus or Thor to spare you from the storms when you know that storms are predictable and explained by natural phenomenon.

The growth of monotheistic religions was also supported by government. It is much easier to control a single hierarchical church and the people that follow it than it is to manage people of varying belief systems that may come to physical confrontation. Political leaders made certain religions the 'state' religion to promote it and often times to punish those that did not follow.

Its also important to keep absorption as part of this process. Is it coincidence that Jesus' death and birth fall on the same days as major pagan holidays?'s not Absorbing aspects of local religions that are being replaced helps bring people into the new faith.

A good monotheistic example is Zoroastrianism. If you follow any modern monotheistic religion you can thank Zoroaster for starting the trend. Zoroastrianism is arguably the source and predecessor of Christianity, Islam and Judaism. It was mainly followed during the times of the ancient Persian Empires by millions of people, today estimates put the number of followers at under 200,000.


  • Isolated methods of destroying or controlling a religion are unlikely to be long term effective. As @AndyD273 mentioned persecution is not a great way to get rid of a religion...humans are stubborn like that.

  • It takes time. You are not going to be able to plausibly kill off a religion in less than 2 or 3 generations (at a bare minimum).

  • They can always come back. Unless it is somehow completely forgotten (which is virtually impossible, especially in the modern era) there will likely be people who keep following the faith.

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Comments are not for extended discussion; this conversation has been moved to chat. – Monica Cellio Jan 20 at 23:40
Okay, but there is no substantial evidence that Zoroastrianiam provided a basis for other religions. – XandarTheZenon Jan 21 at 4:32
It would be more accurate to say that Jesus' birth is celebrated on/near a major pagan holiday. It isn't uncommon to cite the birth as well before Christmas, for a variety of reasons. As for the death, it follows Passover. If you want to make a claim about that being near a pagan holiday, you'll need to go back much further. – jpmc26 Jan 21 at 5:25
Christianity also wasn't "government sponsored" for the first 300+ years of its existence. Rather the opposite, in most of the Roman world for a large portion of that time. Storms weren't really predictable until the advent of the telegraph, and true forecasting requires computer modeling - long after Zeus and Thor were supplanted. General knowledge of weather patterns has been around for millennia, including some rudimentary understanding, which didn't dent belief, however. – Clockwork-Muse Jan 21 at 8:37
Folks, please take the discussion to the chat room that was already created. If you right-click on the timestamp for a comment you get its URL, which you can paste into the room. Expect these comments to be deleted in the not-too-distant future. – Monica Cellio Jan 22 at 20:13

There are a few different methods I can think of that would allow a large religion to entirely (or almost entirely) die out.

  1. Genocide. Other religions have actively and purposefully decided to exterminate the religion. This doesn't have to simply be the extermination of followers of that religion, but rather a purposeful attempt to eliminate the religion.

There are a number of historical examples of attempts to exterminate religions, but probably the most relevant historical examples would be the willful extermination of the religions of Native Americans. When the Spanish conquistadors arrived, their destruction of the Native civilizations - through extermination, disease, enslavement, and forced religious conversion essentially eliminated those religions entirely.

  1. Schism. The religion fragments into multiple sects. Over time, the individual sects diverge to the point that neither truly represents the original religion. Examples of this would be the Orthodox / Roman Catholic schism, the Protestant Reformation, or the fracture of Islam into Sunni and Shiite sects.

Over time, cultural shifts could reduce the number of followers of the original religion to the point that the original religion no longer exists. This will likely involve appropriation of practices of the original religion.

  1. Subsumation. Rather than a schism, a new religion may come along that absorbs the followers of the original religion. As a substantial number of followers convert to the new religion, the original religion is eventually reduced to nothing.

Real life examples of this would be subsumption of the Celtic polytheism religions by Christianity.

  1. War. While this would technically fall under genocide, a particularly bloody war - like a modern nuclear war - could effectively destroy a religion if the followers of that religion were sufficiently localized.

I suppose complete extinction of humanity would be a trivial solution to the problem of 'how to destroy a religion' as well.

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The Native American religions didn't fully die out, they got integrated through persecution. Even today you can find, in rural areas, people praying in a church in front of a statue of St. George... but addressing their prayers to the horse. – Davidmh Jan 22 at 11:19
That's a load of nonsense. i doubt there are a dozen statues of St. George in churches in the US in its enitrety and most of those would be in the cities. Protestants don't go in for statues, and Catholics don't have mounted statues of saints. The US never spent a lot of time persecuting the Native American religions. They just persecuted the people. – Oldcat Jan 22 at 23:56

TLDR: celibacy through reformation.

One possibility is that the religion, at its core, is unsustainable. For instance, the Shakers sprung up during a time of religious fervor (can't remember what that was called). Wikipedia claims that At its peak in the mid-19th century, there were 6,000 Shaker believers; last I checked, there were about two of them left. This was due, in part, to people like Mother Ann Lee being hard acts to follow, but also due to the fact that the Shakers were celibate. No new Shaker babies means they had to rely solely on new recruits, who eventually stopped coming as interest waned.

Now, the fact that your religion got to 1 billion followers probably means that its members can breed. But it's possible that over time, that could change; just like Catholicism underwent many changes after the Vatican II, perhaps the leaders of your religion thought it was time to shake things up (pun intended).

If they start calling for wholesale celibacy for all followers, there will be two effects: one, the faithful will stop breeding, and two, the casuals will leave. This will give you a big initial dropoff, followed by a gradual drain over a few generations. Eventually, like the Shakers, there should only be a few left.

As for why anyone would call for celibacy, well, it depends on the tenets of your religion, and the culture that surrounds it. There have been a few cases of celibate Christian sects that thought an end to sex meant an end to man's domination over women (again, going off the Shakers, they were all about sexual equality, also the Acts of Paul and Thecla seem to imply that celibacy empowers women). Other religions tend to discourage sex since it's an indulgence in non-religious pleasure. I'm sure there are more reasons, but honestly you could make up just about anything and in the right circumstances, people would believe it.

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Na, I don't think that would work on a large scale. Look at the christians: They are not allowed to have sex before marriage, yet I know no Christian who really had never sex before marriage and I know lots of Christians, since I'm living in a christian country (even some "real believers"). – Bounce Jan 21 at 10:25
That's really just an example of difficult standard. That you haven't met any who abide by it doesn't mean that there aren't millions who do. More priests are celebate than pederasts in Catholic hierarchies. They just aren't either newsworthy or interested in talking about it as common discourse. I don't see how your counterargument is compelling. By what definition would you declare someone's faith "real" if not how it effects behavior? – The Nate Jan 21 at 12:40


If rituals with dead are important in your religion, and some highly infectious disease like Ebola comes around, the only solution is to abolish the religious practices. Which might be possible if a secular scientific civilization is nearby, and develops and enforces new rules.

If mortality is high enough, whole civilization will collapse before new rules can be developed.

Even now, some infections like polio resist eradication because some countries resist eradication efforts. See

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Present the followers overwhelming, undeniable proof their religion is dead, such as:

  1. The Great Spaghetti Monster, a beast the size of the moon, appears in orbit carrying the broken bodies of Zen, Sunni, God, Jesus, whoever. "I have crushed your gods. Worship me!"

  2. Time travel is invented and it turns out Zensunnistianity is a load of garbage invented by a cabal of greedy tea merchants.

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Welcome to the site, @steg! I edited your answer ever-so-slightly so the top line reads like an answer, so your intended meaning is more obvious. At least, that's what I hope I've done. If my edit is not what you meant, please feel free to revert it! – type_outcast Jan 21 at 0:15
The body of Zen? There's an interesting mental image. – The Nate Jan 21 at 12:47
@TheNate The Zen which has a body is not the true Zen? – pydsigner Jan 21 at 18:07
That's not the moon, it's a noodle pointing at the moon. – The Nate Jan 22 at 3:13

One could try to answer with memetics by comparing it to genetics.

In this model, it proves very difficult to have 1 billion followers of an identical religion, when you look closer you will see sects, sub sects, divisions, internal fighting and suchlike. And a major religious identity like the abhramaic religion has many many divisions such as the three massive divides of Islam, Christianity and Judaism.

Continuing on the evolutionary model, you can see that it's basically impossible for the state of the religion in its present form to remain stable for very long at all. It will grow, shrink, adapt, different sects will speciate and recombine over time such that the beliefs of this population 1000 years from now will be more or less entirely incompatible with the state it's in now. And if you look at the behaviours, biases, practices of today's religions 1000 years ago, you will find them to be abhorrent compared to what we have now.

So to answer the question, yes, the religion of today will die out, but most likely due to it morphing into something different.

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Not sure if this is too dark, but how about Mass Suicide? You could have the religion believe a comet is a god, and the only way to join him is to commit suicide at the right time (or make up whatever reasoning you want). You could even have someone from the religion rise up as a prophet and call everyone to do it. Those that do, die, those that don't, probably will mostly switch religions.

This has happened before

Edit: You could also make it so one of the leaders and a smaller group of followers believes the mass suicide is necessary. Then they could poison the other people without them knowing because they're afraid the followers won't have the stomach to do it themselves. (They could do this by poisoning a wine the entire group is required to drink on a holiday. The wine could be produced by the leading body of the religion, so they have easy access in order to poison it).

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It seems like scale is an important part of the original question, and Heaven's Gate didn't claim a billion followers. Any reasoning to supports your theory working at such a large scale? – nitsua60 Jan 21 at 2:59
@nitsua60 Consider that a religion that teaches peace had 2/3 of the male European population go on a suicide killing spree during the crusades. Consider that 1 billion present-day people will rather let a child starve than eat a cow because cows are holy animals. Another billion will eat cows, but not pork. That same billion believes that the body must be buried intact or the soul finds no peace. But it's OK being torn to pieces by an explosive belt, in return you get 12 virgins. No soul problem there. Do you really think there is anything absurd enough so a billion people won't pick it up? – Damon Jan 22 at 12:58
@Damon these are good points--I hope Martin_xs6 incorporates some of them! – nitsua60 Jan 22 at 13:42
There is a difference between "absurd" and "suicidal." There's a reason that of the second billion, only a small, antisocial fraction want to blow themselves up. – Jonah Jan 22 at 19:30
@nitsua60 Does the edit address the scale problem? – Martin_xs6 Jan 22 at 20:12

Irrelevance would be my top vote.

Organised religion is a minority interest in Europe, and in the West generally. People (and countries) tick the "Christianity" box in surveys by default, but actual church-goers are a tiny. Wikipedia suggests 10% in the UK, 22% in the US. Go back 50 years and that was high 90-something% for both. People haven't lost their built-in need for "spirituality", but they have recognised that they have no need for organised religion.

I'm not going to go into why it's happened, because that's typically the start of a flame war. Just take the numbers and extrapolate.

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Interesting, i can see how that would lead to a decline, but would it be drastic enough? How about religious renaissances? – Serban Tanasa Jan 21 at 19:15
You could probably say a similar thing about Paganism in Rome. – Oldcat Jan 22 at 23:57
@Oldcat Perhaps, but that got a serious kicking from Christianity becoming the official state religion. The interesting thing for Christianity is that it's faded out without anything trying to take its place. For me, that's ample evidence of the truth of humanism - not only can we run a working system of morality without needing to refer to some holy teachings, but the result is a better system of morality that leaves religions in its dust. – Graham Jan 25 at 16:31
@Serban Tanasa Have there been any in the West? Sure there have been some in the ex-Communist countries, but that's in reaction to an oppressive state religion (communism; yep, that's a religion on the "walks like a duck" rule) suddenly being relaxed, and people being allowed self-expression for once. In the West we've had free choice of religion for a few decades, and the only way church attendances are going is down. – Graham Jan 25 at 16:45

Yes, but it would take a considerable amount of force to do so, and would probably have to be replaced by something else. Henry VIII did something similar when he wiped out Catholicism. To achieve this, he shut down all catholic monasteries, churches and forced the new members into anglicism. He was successful in his effort and managed to establish himself as the new head of the church

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Didn't work, even just in England, so that's a useless example for anything besides the great difficulties involved. He triggered centuries of wars and there are still Catholics in England. – The Nate Jan 21 at 12:43
Actually religion thrives on persecution. – user1751825 Jan 22 at 6:29

Some of it depends upon the tenets and the tenor of the movement and its adherents current context at the time of the start of the decline. This is question begging as I am assuming your question is possible.

For example, some historical times in a religion's history could be more mystical in nature versus a more empirical time period. It depends a lot on how the person and culture defines truth.

For example, Christianity. It has gone through many periods and some times in that history collapse might have happened, but for differing reasons. Today, many cultures are more relativistic, but in some area empirically based, etc. Yes those are sweeping generalizations and not exhaustive.

But, for the sake of argument, lets say you could produce the body of Jesus. Christianity would collapse. That's its entire base. And, you'd have to have a culture that would believe that is the reason for its existence and the continued requirement for its existence.

This is not to debate anything. I promise. It's just to look at the complexity of what you are asking. So, maybe you could have some prime condition that created the religion and therefore you can create, perhaps, the demise of that religion. It depends upon the complexity of your system.

You could do this with any religion. If the current cultural milieu would allow it. The timing of everything would have to be perfect.

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Aliens turn up. This would totally demolish most if not all world religions dependent on an earth centric view. In fact it would probably lead to science becoming the dominant "religion" of choice, or more specifically a belief in the Standard Model (Revised 2018 Edition) being THE explanation for all phenomena in the Universe.

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Yes, it is conceivable, thanks to a little thing called Education.

See Christianity in the USA.

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This does not answer the question, adds nothing to the conversation, and is needlessly inflammatory. Graham's answer by way of contrast is none of that. – Jared Smith Jan 22 at 19:00
Incorrect, Grahamas post steadfastly refuses to answer the question and thus is not an answer. Perhaps his fear of downvotes is stronger than mine, but I am not going to shy away from giving the correct answer because some people do not want to hear it. I explained a real world example where exactly this is happening and thus answered the question. – Scott Jan 23 at 22:11
Public education in America has a long history. The decline of Christianity in America started a mere handful of decades ago. The reasons for that decline are varied, whole books have been written on the topic. The quality of American public education is arguably worse now than it was at Christianity's peak, again for reasons that are far too lengthy to explore here. So education cannot be the cause. Nor is any of this relevant to the question, which is how to construct this sort of situation in a narrative without writing an entire book on just the backstory of how it happened. – Jared Smith Jan 25 at 13:23
I don't mind downvotes, but I'd like them to be because I'm wrong, not just because of dogma. ;) Christianity has been on the slide since WWI demolished a lot of Western certainties, and WWII took that further - not education, but a change in social attitudes. Europe was where that demolition took place, and it's no accident that Europe is further down that road than the US, although the US has its own battlegrounds in civil liberties. The narrative of how to get there is long and conflicted. But I don't have to cover all that - all I have to do is show it happening. – Graham Jan 25 at 16:40

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