I was playing on nation level. I had three cities each with 3-4 territories attached. I selected Shamanism. I had converted the other person (human) on my continent by the Classical era. I had two tenets and all the holy sites I could build. I met another person (AI) to my west early in the Classical era and his cities were taking on my religion a little bit, and mine were taking on his a little bit. So far so good. Then, my scout traveled through shallow water, crossed the New World continent, passed through shallow water again, and met a fourth person (AI). The very next turn, my capitol (with holy site), my second city (directly adjacent to my capitol), my third city (a couple territories away from my capitol) and my fourth city (with two holy sites) were all 30-50% converted to the fourth person's religion. That nation was nowhere near me, and we weren't trading. So exactly how is it that my cities were converting to the religion of someone I had literally just met? This makes no sense. Further, as a player, there is nothing you can do about this passive spread that appears out of nowhere. Tbh, I wish I could just shut religion off entirely until it is fixed. It is extremely not fun to take the 3 faith per territory civic, build every holy site I can build, and take the fanatical choice on every event only to have my religion melt like butter the turn after I meet someone on the other side of the world.

I met this AI the turn before. We were not trading. Even if we had been (which, again, we were not), why should trade routes convert 30-50% of all cities in a nation in one turn when the source is halfway around the world? There should be no mechanic that makes something like this occur.

Further, in taking a closer look, this AI had zero real holy sites. It had Stonehenge, a single tenet, and two cities (pop 10 and 12). I had three cities (pop 27, 15, 15), and up until meeting this AI they were solidly my religion. So if religion were going to spread, it should have been in the other direction. The other human player in the game had not met this AI, but the turn after I met it, a couple of their cities began converting to the AI religion too. It's completely buggy.

Can you post some before-and-after save files? I haven't seen anything like this.

From my experience having Harbors is enough, no need for trading.

Guys, my cities tanked 30-50% in one turn. No matter what the mechanic is, this doesn't make any sense. No passive mechanism should change things this drastically in one turn whether you're trading or not, neighbors or not, or anything else. The AI didn't have some extreme faith. She's Carthage, we're in the Classical era. I don't think this is a bug, on further looking. I think this is by design, unintentional or not. It's just poor design.

I still think a dramatic shift like that within one turn is a bit much, especially in the Classical era when, presumably there would be no way to communicate anything that quickly, let alone build up  interest in a foreign religion.

As Krikkitone said, "building up" is modelled in the time required to flip, which is affected by difficulty level and civics. You generally have time to intervene, perhaps by building a Holy Site, acquiring a Faith civic, or building an ED that provides Faith.

I think the current mechanics are good. Religious struggle is a real thing, especially at higher difficulty levels. In particular, "snaking" out to grab a resource-rich territory can put you in a disastrous religious/cultural position where your isolated territory gets swamped by foreign influence. Historically, that's as it should be IMO - ancient empires tended to form geographically coherent regions, not gerrymandered districts placed to grab the Ebony. 

Having a nation take on this kind of influence one turn after having their scout run into someone else on the other side of the world in the Classical era is silly. That isn't "religious struggle." It's a contrived mechanism that breaks immersion.

There was no means of swift communication in the Classical era that could travel through an entirely empty continent and over the sea to some other country. It's things like this that cause people to dislike the game. It's illogical and unrealistic. Religious struggle is osmosis from someone in proximity. Instant osmosis is a bad idea under any circumstance, but in the eras pre-dating any kind of intercontinental communication it's utterly ridiculous.

I did not "snake out" to grab anything. My scout bumped into this nation while passing through exploring.

AOM wrote:

Having a nation take on this kind of influence one turn after having their scout run into someone else on the other side of the world in the Classical era is silly. That isn't "religious struggle." It's a contrived mechanism that breaks immersion.

There was no means of swift communication in the Classical era that could travel through an entirely empty continent and over the sea to some other country. It's things like this that cause people to dislike the game. It's illogical and unrealistic. Religious struggle is osmosis from someone in proximity. Instant osmosis is a bad idea under any circumstance, but in the eras pre-dating any kind of intercontinental communication it's utterly ridiculous.

I did not "snake out" to grab anything. My scout bumped into this nation while passing through exploring.

The thing is that 30-50% "influence" of the foreign religion means exactly 0... ie they are at 50% and it does Nothing to any of the religions in your territories because you are at 50%, and your religion will stay unless they are able to increase their share to 60% by building New Holy Sites/Faith EQs or getting additional routes through your empire.  (a bug is possible.... but a new trade route connection that suddenly became available because you explored it is another possibility)

AOM wrote:
Instant osmosis is a bad idea under any circumstance

I don't know what else to say. I don't know what you want or why you want it. It's not "instant osmosis". You have time to react... probably 6-10 turns, which is quite a lot of time. And that's if the opposing influence even gets far enough to actually flip your territory. You seem to be taking a great deal of offense to your territories being "30-50% converted", but those numbers *don't matter*. If you have majority religious influence in a territory then it won't flip. Ever. If you don't, then it *will* flip... eventually, with time for you to react. What do you want? For your religious control to be impenetrable once you've established it? That's what it sounds like.

What I want is for the game to make at least some sense. Religion cannot travel through a completely empty continent and across water. For it to do so is ridiculous. This kind of nonsensical mechanic is why this game is doing so poorly. People want things to make sense. What ostensible explanation is there for this scenario? 

A scout travels through shallow water, passes through an entirely empty continent, passes through shallow water again in a time when there is no means of communication across this vast space. He runs into another nation. And instantly, the nation back home, a nation he hasn't seen in years, is suddenly not only fully aware of this other nation's religion, but also influenced by it. 

What is the mechanism? There is no mechanism. Just very, very poor game design. Instant osmosis is stupidly unrealistic in this scenario. And, what's even more silly, is this probably happened because the AI chose cats instead of ferrets. Just plain ridiculous.

If you want it to make sense provide more specific information about trade routes and harbors (eg screenshots) so folks can help explain whether the mechanic is working as intended or looks like a bug 

None of that matters, although you can read my first post for details. I cannot remember if I had harbors in my cities. It is likely that I did. But, a single turn for religion to influence mine, from another continent separated from me by the "new world" which was still empty with open water on each side of it, in the Classical era, is, on the face of it, nonsense, harbors or no harbors.  And, what is the solution if the issue *was* that I had built harbors? Just...build no harbors? Are we supposed to think that harbors, in and of themselves, are magical religion channels capable of directing super-potent religion waves in a time before there was any sort of instant intercontinental communication? Or did 1000 invisible evangelizers pour forth from the foreign nation and instantly teleport themselves to my cities? Trying to make this somehow a logical outcome of my scout stumbling on this far away country requires imagination gymnastics that are immersion breaking.

I would get it if I had placed an outpost on another continent near an established nation and the outpost became influenced by the nearby religion, but I didn't. My scout was just passing through.

What I am saying is that no matter what the circumstance, this kind of instantaneous intercontinental delivery of religion during the Classical era does not make sense, intentional or not.

I'm not posting to ask for an explanation of how things work. I get how things work. I'm saying it still seems broken. Religion should not hurl itself through empty land and over empty seas to influence a nation 1000s of empty miles away one turn later in an era when there is no intercontinental communication. Again, I do not need an explanation. I am saying it is mechanics like this, illogical and silly, that make people not like the game. It seems buggy even if it's intentional. I hope this time, my point is clear, so you will stop feeling obligated to tell someone how things work when the person you're talking to has been playing this game through multiple iterations since last spring.

AOM wrote:

I'm not posting to ask for an explanation of how things work. I get how things work. I'm saying it still seems broken. Religion should not hurl itself through empty land and over empty seas to influence a nation 1000s of empty miles away one turn later in an era when there is no intercontinental communication. Again, I do not need an explanation. I am saying it is mechanics like this, illogical and silly, that make people not like the game. It seems buggy even if it's intentional. I hope this time, my point is clear, so you will stop feeling obligated to tell someone how things work when the person you're talking to has been playing this game through multiple iterations since last spring.

I agree the UI is not particularly good, if they could show the trade routes in the religion/sphere of influence screens that might help.  If it showed you that your holy site territories were on the middle of a trade route from another holy site territory, then it would make more sense.