I think the manual and civilopedia are too vague on how this works, so I'm hoping some knowledgable persons can help me out with clearing the confusion about this. Some of these questions are sort of connected...
1. What exactly is the "influence" on the religious advisor's screen? Is it only affected by the number of cities with the religion and the size of these cities? Or also whether other civs have it as state religion, and how powerful those civs are? Do monastaries, temples and cathedrals in your cities boost the "influence" by boosting the culture your religion generates?
2. Is a trade network connection by roads/rivers/coastlines absolutely necessary for the spread of religion, or does it only affect the speed of the spread?
3. If I'm the founder of a religion, it seems to spread to my own cities fairly quickly. Is the spread slower between the cities of non-founding civilizations (assuming that none of those civs' cities have any religion at all), even if they are as well connected as my own cities, and at same distance (number of tiles) from the holy city?
4. If you count aside missionaries, does a religion ONLY spread from the holy city and outwards, or from any city with the religion? I have sent missionaries to far away cities of other civs, but does the religion spread on from there to adjacent connected cities? In other words, can you with a missionary spread religion in a single city on another continent, and then watch it sprawl across the entire continent eventually (during a considerable time, but still), without any other active measures on your behalf? I have never noticed that this works myself.
5. Does the spread of religion slow down or stop to halt after a certain technology or civic? After a certain distance from the holy city? I get the impression that when I reach the medieval times or so, my religion doesn't seem to spread outwards any more.
6. The manual says that "some religious buildings increase the speed at which a religion will spread", but it's not very clear how, except by the creation of missionaries. How does this work? Do monastaries, temples and cathedrals actually speed up the spread? If so, are they more important in border cities than in core cities?
7. Related question: Does your cultural output (i.e. your cultural superiority/inferiority compared to your neighbouring civs) - by religious buildings or otherwise - affect how fast your religion spread to your neighbours? In other words, are they more likely to adopt your faith if they are awed by you?
8. How does the mechanism for whether a city will adopt the religion work?
In a recent game I founded Hinduism. It spread to my nearest neighbour, the Spanish, who adopted it as state religion. After most of the map and the other civs had been discovered, I noticed that Hinduism had spread to all Spanish cities except the one furthest away from me, Cordoba (which had adopted Buddhism from a third party). I had even planted Hinduism in some cities beloning a third civ on the other side of the Spanish.
So, Cordoba was completely surrounded by Hinduist cities, every other Spanish city was Hindust and Hinduism was also their state religion. Still, the city never adopted Hinduism. I didn't bother with missionaries, because I was sure the city would adopt it any turn, as overwhelming as the surrounding pressure of Hinduism seemed, but it never did. I got the impression that the game rolled a die when the Hinduist influence had reached Cordoba: Will Cordoba adopt Hinduism? The result was no, and then the game never rolled the die again.
In other words: Will a city (without theocracy) eventually adopt a neighbouring religion through the sheer grind of time, or will it never adopt a religion once it has "rejected" it? Also, what are the modifiers if a city already has a religion, or two religions, or three, and so on? Or is a missionary the only way to spread a religion if it already has another one?
Thankful for answers.
1. What exactly is the "influence" on the religious advisor's screen? Is it only affected by the number of cities with the religion and the size of these cities? Or also whether other civs have it as state religion, and how powerful those civs are? Do monastaries, temples and cathedrals in your cities boost the "influence" by boosting the culture your religion generates?
2. Is a trade network connection by roads/rivers/coastlines absolutely necessary for the spread of religion, or does it only affect the speed of the spread?
3. If I'm the founder of a religion, it seems to spread to my own cities fairly quickly. Is the spread slower between the cities of non-founding civilizations (assuming that none of those civs' cities have any religion at all), even if they are as well connected as my own cities, and at same distance (number of tiles) from the holy city?
4. If you count aside missionaries, does a religion ONLY spread from the holy city and outwards, or from any city with the religion? I have sent missionaries to far away cities of other civs, but does the religion spread on from there to adjacent connected cities? In other words, can you with a missionary spread religion in a single city on another continent, and then watch it sprawl across the entire continent eventually (during a considerable time, but still), without any other active measures on your behalf? I have never noticed that this works myself.
5. Does the spread of religion slow down or stop to halt after a certain technology or civic? After a certain distance from the holy city? I get the impression that when I reach the medieval times or so, my religion doesn't seem to spread outwards any more.
6. The manual says that "some religious buildings increase the speed at which a religion will spread", but it's not very clear how, except by the creation of missionaries. How does this work? Do monastaries, temples and cathedrals actually speed up the spread? If so, are they more important in border cities than in core cities?
7. Related question: Does your cultural output (i.e. your cultural superiority/inferiority compared to your neighbouring civs) - by religious buildings or otherwise - affect how fast your religion spread to your neighbours? In other words, are they more likely to adopt your faith if they are awed by you?
8. How does the mechanism for whether a city will adopt the religion work?
In a recent game I founded Hinduism. It spread to my nearest neighbour, the Spanish, who adopted it as state religion. After most of the map and the other civs had been discovered, I noticed that Hinduism had spread to all Spanish cities except the one furthest away from me, Cordoba (which had adopted Buddhism from a third party). I had even planted Hinduism in some cities beloning a third civ on the other side of the Spanish.
So, Cordoba was completely surrounded by Hinduist cities, every other Spanish city was Hindust and Hinduism was also their state religion. Still, the city never adopted Hinduism. I didn't bother with missionaries, because I was sure the city would adopt it any turn, as overwhelming as the surrounding pressure of Hinduism seemed, but it never did. I got the impression that the game rolled a die when the Hinduist influence had reached Cordoba: Will Cordoba adopt Hinduism? The result was no, and then the game never rolled the die again.

In other words: Will a city (without theocracy) eventually adopt a neighbouring religion through the sheer grind of time, or will it never adopt a religion once it has "rejected" it? Also, what are the modifiers if a city already has a religion, or two religions, or three, and so on? Or is a missionary the only way to spread a religion if it already has another one?
Thankful for answers.
