In earlier versions of Civilization, the role of religion was basically to serve as the Opiate of the Masses. If a city was getting too much unhappiness, you could pacify the citizens by building a Temple or a Cathedral, and each of them would make some number of citizens more content. There was never a named religion of any kind, let alone any notion of competing religions. As you might imagine that could be a delicate subject so I can understand why they did it this way. Nevertheless, it is hard to picture the sweep of history without religion entering into it at any point.
In Civ IV this begins to change. There are a number of competing religions, though I don’t think what they do is really competing at this point. That will come later, particularly in Civ VI. But the religions we have here are:
The way you get a religion in the first instance is by being the first player to discover a key technology. For instance, the first player to research Meditation will get Buddhism. This is a very early “tech”, which presents a strategic question for you: Is researching Meditation early on the best use of your scientific research when techs like Animal Husbandry or Hunting are out there waiting to be discovered? For me the answer is often “No”, and so I never am the one to develop Buddhism. And in any case, one of the AI players will get it pretty quickly. I may elect to convert to it later, or indeed to any other religion, and it can be beneficial. In fact I would argue that it doesn’t matter in general which religion you end up with. Where the choice of religion really matters the most is in Diplomacy, where it can be key to either good or bad relations with other players.. So it is a step forward, but not a revolutionary one, in my view.
The main benefit to founding a religion is that you get to have a Holy City for that religion. This does give you some benefit, in that a Holy City will receive 5 Culture, instead of the usual 1 for a city that merely has a religion. And if you have a Holy City, a Great Prophet can be used to build the Shrine appropriate to that religion.
When a city adopts a religion, you can build religious buildings in it. For all religions, the initial building you can build is a Monastery. It gives you an additional 10% Science generation in the city, though that expires when Scientific Method is discovered. You also get 2 additional Culture, and you can build Missionaries, and these benefits do not expire. Note that you can build a Monastery in the city for any religion that is present, so you could conceivably build 7 different Monasteries of you had all 7 religions. Monasteries can be built as soon as you discover Meditation.
The next level is the Temple. Every religion can build Temples as soon as you discover Priesthood. Each Temple adds one additional Culture and makes one additional citizen Happy. Also a Temple can turn one citizen into a Priest, who is one of the Specialist citizens you can have. As with Monasteries, you can build a Temple for every religion that is present in the city
The third level is the Cathedral, though in this case the names change to be specific to the religion. And you can build some twice as fast if you have the right key resource available. Here are each of the Cathedrals and the key resource needed to build them twice as fast.
- Buddhism – Stupa – Copper
- Christian – Cathderal – Stone
- Confucianism – Academy – Copper
- Hindusim – Mandir – Marble
- Islam – Mosque – Marble
- Judaism – Synagogue – Stone
- Taoism – Pagoda – Copper
Cathedrals offer you a 50% increase in culture in the city, make two citizens Happy if this your State Religion, and make one citizen Happy if you have Incense available. And they can turn 2 citizens into Priests. However, you cannot build as many Cathedrals as you can Temples. A temple is required before you can build a Cathedral, to be sure, but then it comes down to one Cathedral can be built for every X Temples. And X is determined by the map size you are playing on, ranging from 2 on small maps to 4 on huge maps.
Monasteries, Temples, and Cathedrals are all buildings you can build if the given religion is present in one of your cities. There is an additional level that can be built in Holy cities, and that is the Shrine. Each religion has a Shrine particular to it, but you don’t build it the way you build other buildings. Instead, you have to generate a Great Prophet, and the Great Prophet can be used to create the Shrine. And while each religion has its own name for its Shrine, the effects are the same for all of them. You get 1 added gold per turn for every city following the religion, and having the Shrine will itself help to spread your religion. And a Shrine can turn 3 citizens into Priests.
Spreading Your Religion
If you have invested the resources into building up your religion, you will probably want to spread it. You can do this in several ways, but one of the first ways you can do this is with Missionaries. You can train Missionaries as soon as you build a Monastery, and send them out to spread the good news. There are two other ways religion can spread, though. One is through Diplomacy. When two players are engaged in Diplomatic discussions, one of the agreements that can result is that one player adopts the other player’s religion. This will increase the closeness of the relationship in general, but can also happen when there is a marked power imbalance such that a strong player can bend the weak player to his will. But if you had never adopted a religion because you focused on other things, it might be advantageous even if you are not a weak player. In addition to building the relationship, it would unlock some development paths if you wanted to build more Temples, for instance.
There is also Automatic spread. If there is Trade access between your Holy City and another city that has no religion present, there is a chance for your religion to spread to that city. Or conversely, you might discover that one of your cities just adopted a religion from a neighboring player, and that might be an example of Automatic spread. The chances of this happening can increase if the cities are close to each other, and will further increase if the Holy City has Shrine present.
The other way is to train those Missionaries and send them out to spread the Holiness to those heathen savages, or even to any of your own cities that don’t have a religion yet. A Missionary is a non-Military unit that has no military strength, but otherwise can move around, see things, an so on. And when it enters a City which does not have the religion of the Missionary, a button shows up to Spread Religion. This will not necessarily have the same result each time, since there is a probablility of success based on whether it is your city or another player’s city, and also based on how many other religions are present in the city. And regardless of the outcome, the Missionary is “consumed” and eliminated in the Spread attempt. You can always try with more Missionaries, but note that no city can have more than 3 Missionaries at any one time, counting both the ones that are trained and active as well those in the queue to be trained.
One option available to you is to declare a State Religion. This is like England, in which the Anglican Church is official state religion. You can do this if you have one or more cities following the religion. This can give you additional benefits. Each city following the State Religion will have one additional Happy citizen (or 2 additional if you have a Cathedral of the religion present), and will generate one additional Culture each turn. But in addition you can have added effects from certain Civics and Wonders. If you have the Organized Religion Civic, every city following the State Religion will have plus 25% production for Buildings and Wonders. With the Theocracy Civic, you get 2 additional experience for all military units produced in the city. And with the Pacifism Civic you get plus 100% Great Person points produced.
For the Wonders, the Sistine Chapel produces Culture bonuses, the University of Sankore produces Science bonuses, and the Spiral Minaret produces gold bonuses when combined with State Religion.
So, should you invest a lot of energy into promoting a religion? That depends on how you are trying to win the game. Recall that with Civ IV you now have more options than just military conquest or space race. This will get better in future versions, but in this version it opens up some interesting options. You can always just ignore religion, and you can be successful. But religion is in the game, and your cities will adopt religions even if you take no action to promote it. There is no such thing as a religious victory in Civ IV (that will come later), but you can use religion to aid in your quest for victory. The most important place where religion is useful is in attaining a Culture victory. When you see how all of your Monasteries and Temples produce additional Culture, and that you can build them in any city where that religion is present, you can see how this adds up. Then adopt State Religion and build the Sistine Chapel, and you get an additional boost. Adopt the Pacifism Civic and you can double the production of Great Persons, and many of those will be Great Artists since you are on the Culture path.
If you are going for a Military type of victory, religion can be useful as well. Monasteries give a Science boost, and you need Science to produce the best units. And the added Happy citizens from religious buildings can counteract the war weariness that might otherwise hamper your military campaign. And if you have a State Religion and adopt the Theocracy civic all of your units will be more powerful right from the start.
For my part, I don’t find that I know enough to predict what kind of victory I will go for in the early game, which is when religions are generally “discovered”, so I don’t usually make a bee-line for a religion. But it is an important part of the game, and you should learn to use it to your advantage.