One True Faith

The phenomenon in which a work of Science Fiction or Fantasy has only one religion (The Church) in it; furthermore, there are never any factions of it, or different interpretations of its belief.

This is related to Law of Conservation of Detail. The lack of other faiths doesn't particularly break Willing Suspension of Disbelief, so why bother? Having said that, it's inherently unrealistic; our planet has seven or ten major religions in the modern day alone (some founded individually and others spun off from existing ones), and other religions have come to prominence and since died out. But no one ever questions this when it happens, making it either an Acceptable Break From Reality or something too controversial to touch with a ten-foot pole. It is most justified in works where much more is known about the spiritual world than in Real Life, and there's lots of evidence to back it up to the point that not believing in this faith would make one a Flat Earth Atheist (though that still doesn't explain the lack of factions; there is no hair so fine that people won't try to split it).

Ignore Outgrown Such Silly Superstitions. But also could be Supertrope or Mindset and Christian variant for Christianity Is Catholic.

As discovered during the YKTTW process, this trope is more of a Sliding Scale than a straight trope, since there are numerous aversions and subversions. We'll go in order.

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Literature

• The Sword of Truth
  • Not true. There are several religions in that series and one of them has several different factions who violently disagree. Played straight in that each racial or cultural group only has one religion.
• The Wheel of Time, arguably. See "subversions" below.

Video Games

• In Tales of Symphonia, two entire worlds share the same religion with only minor cosmetic differences. Justified by the Big Bad having created and actively running both. Although the village of Mizuho has its own gods.
• Dead Space has Unitology, which is specifically mentioned to be the only religion that has survived into the timeframe of the games. It is mass low-level Mind Control by the Markers, preparing humanity to be turned into Necromorphs. It seems to be primarily modeled after a certain controversial religious movement in the United States, though the writers have said it's based on religious cultism in general.
• In all Tropico games except Tropico 2, the only religion is the Catholic Church. This is justified since the games are set on Spanish-speaking islands in the Caribbean, which are very much Catholic country.

Real Life

• This can be Truth in Television with most New religious movements that didn't too organized (like having lack of believe different interpretations of their holy book or no having skeptics to challenge their religious authority as examples) or having bigger follower population enough to split yet like aforementioned Church of Happyology as they tires sued any organizations or groups for promoting their "Holy relics" without their approval as not Happyologists or having connections to Happyology or their founder's teachings, but it didn't stop few people to tried subverted this as calling themselves as Independent Happyologists.

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Anime and Manga

• Zero no Tsukaima played with this, in the fact that humans have one religion, based off on Crystal Dragon Jesus version of Christianity in the Fantasy Counterpart Culture of Vatican, Romalia. However, it is not the only religion per se, as the Elvens follow a different one. This becomes a plot point in the third season.
• To Aru Majutsu no Index has just every religious denomination that's present in the real world in its world as well. They're all true, and each has its own magic.

Fan Works

• In Empath: The Luckiest Smurf, nature worship with Mother Nature as the patron deity of sorts is the religion most Smurfs worship, with Christianity and the religion of the Psyches being minority religions.

Literature

• Discworld, with its proliferation of Physical Gods
• A Song of Ice and Fire, which has featured five in four books alone.
• His Dark Materials, even though The Church gets all the attention
• Wicked, at least in the original book
• In Orcs, not only are there several religions (mainly a monotheist and a polytheist one), but they are very important in the plot.
• Ender's Saga where matters of ensuring freedom of religion are plot-significant at some point.
• In the Left Behind series during the Tribulation, there's the pantheistic mishmash of all world religions called Enigma Babylon One World Faith as the official one-world religion, but there's also Christianity (as defined by the books' authors and the Tribulation Force characters), Judaism, and Islam (which in the book series ends up being a minority religion), which all become illegal to practice even when Enigma Babylon is replaced by the Luciferian-type state religion of Carpathianism around the midway point of the Tribulation. In the Millennial Kingdom, Christianity becomes the official one-world religion, though dissidents are permitted to practice the beliefs of the Other Light despite the fact that (1) it's totally in error when it comes to believing Satan is going to defeat God and Jesus by the end of the Millennium and (2) those who remain unbelievers in God and Jesus Christ by the time they reach 100 will instantly die and go to Hell.

Tabletop Games

• Exalted: While the Immaculate Order would certainly love to be the One True Faith, the plain fact of the matter is that human nature and the cosmology of the setting works against it. As it is, they only really have this status on the Blessed Isle, and only there because they ruthlessly suppress any hints of non-Immaculate leanings.

Video Games

• Xenogears features two distinct major religions, (very) briefly hints at a third in one scene. Most of the beliefs of the organized religions, however, seem to be based upon a similar set of concepts.
• World of Warcraft has multiple religious faiths, many of which are diverse from one another.
  • In the Alliance, the humans, along with the dwarves and the draenei, practice a Crystal Dragon Jesus religion known as the Holy Light. The exceptions are the night elves, who worship a moon goddess known as Elune, possibly the Gilnean worgen, former humans who were brought to the Alliance by night elves (though their religious practices are almost unknown), and the gnomes, who have for the most part completely forgone religion in favor of science.
    • It's noted in the tabletop roleplaying game that Elune is the only true actual deity in the game world, though that sounds like Night Elven propaganda to me.
    • It should be stated that the Holy Light is non-theistic (that is, it has no godhead) and allows for some degree of syncretism.
    • That said, earlier games make references to a more theistic bent, and references to a deity by worshippers of the Holy Light have been seen within World of Warcraft. Given the amount of turmoil that has taken place over the course of the games, it's entirely likely that the Church has undergone theological, philosophical and metaphysical developments.
  • The Horde is split up for the most part. Orcs, as a whole, have a shamanistic heritage. Almost all trolls worship their multiple Loa spirit gods. The tauren worship their tribal deity known as the Earthmother. Forsaken undead have some sort of religion involving the shadow, themselves and the light(to a lesser extent). Blood elves follow the Holy Light. Its unknown what goblins worship but they can be priests.
  • In addition, there are many other races that worship other deities: members of the Cult of the Damned worship the Lich King, many corrupted followers of the Old Gods exist, and there are many others.
• Breath of Fire II, which sports the benevolent but mostly impotent Dragon God, the minor earth deity Namanda and the villainous Church of St. Eva.
  • Repeated in III, with the God of the Urkans (actually the Goddess Myria) and the Dragon God Ladon, who still has a few shrines as the "god of travelers" and serves as a Master.
• The Elder Scrolls. Morrowind, for example, has the Imperial Cult, the Dunmer Tribunal, the native Ashlander religion, and the Dagoth Ur Religion of Evil.
  • However, every culture in the game has basically the same creation myth. They just interpret it differently.
  • The Ordinators random bark of "Three gods, one true faith" has nothing to do with this trope.
• Vagrant Story, with two
• La Pucelle, technically: although the story centers on members of the titular church, there is another one who doubles as its theological rival, enemy and Church of Evil.
• Arc Rise Fantasia has three, although two (North and South Noireism) are kind of variations of each other.
• Final Fantasy X-2, where the former Yevonites have divided into the Youth League and New Yevon. The major bone of contention is the speed at which technology should be incorporated into daily life.

Webcomics

• Get Medieval, with both earthly religions and alien ones.

Real Life

• But of course. Also, nearly every faith is heavily fragmented into several different sects. With Christianity as a clearly notable example if you took Social Studies or Religious Studies classes.

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Fan Works

• In Fallout Fanfiction wiki that there even a lot of single Post-War religions like their canonical ones. However their one such idea as what if Vault Survivor from Fallout 4 did side with Tekus in Far Harbor DLC could result in creating two more "Atomic denominations" in near future after events of Fallout 4, that if Tekus have not just feared by other The Island but also established an Island nation as Atom's Holy Island and split off from Main church (Church of the Children of Atom) as Atomic Orthodox Church to justified his authority from group and later one of their former followers established Anti-Atom organization that hates all Atomic religions to spreading lies.

Film

• Star Wars (Jedi vs. Sith at the very least. The Expanded Universe features enough "alternative" religions to make the franchise an aversion, but we're ignoring those for the moment.)

Literature

• Lord of the Rings, in which certain cultures (or subcultures) greater more emphasis on their favorite members of the pantheon
• Omnianism in Discworld, going through endless schisms after the last prophet, Brutha in Small Gods
• Lois McMaster Bujold's Chalion universe has two religions who are bitter rivals, despite the fact that the only difference in their philosophies is how one particular being fits into the pantheon.
• David Weber's Safehold series is the story of one world's transition from a single monolithic religion to a deeply divided global religion - but it's still the same religion, just divided. The second and third novels in the series are called By Schism Rent Asunder and By Heresies Distressed, which are a fairly accurate description of the fate of the Church of God Awaiting.
  • The reason for the single religion is that it was achieved artificially through massive brain washing and by nuking any opposition from orbit. We do not know what the religious makeup of the original colonists was. Other religions might have popped up over the centuries but they would have been mercilessly wiped out by the Church.
• The Wheel of Time, like Star Wars, has one single monolithic belief system for the whole world - but it's dualistic, and the darker side has a few adherents here and there, and they're the antagonists. Well, the main antagonists. So that darker side might be considered a schismatic completely separate religion or a part of the same religion with different ways of observing it.
  • As typical of Robert Jordan, every side also has different factions: for example, the Children of Light and the Aes Sedai both worship the Light and the Creator, but have a very different view of the One Power... Masema's followers also behave like a fanatical cult, putting Rand on the same level as the Creator.

Live Action TV

• Doctor Who: In the future the army (human army that is) is run by the Church and among the Clerics there are mentions of both Anglican troops and of a Papal mainframe.

Tabletop Games

• Dungeons and Dragons
• Warhammer 40000 has enough cults of the God Emperor that almost everyone is, indeed, a heretic.

Video Games

• In Broken Steel DLC from Fallout 3 have witnessed a recently established new sect from Church of the Children of Atom as Apostles of the Holy Light led by one of their former followers, Mother Curie III over her theological interpretation with seeing Ghouls as a new part of Human evolution.

Western Animation

• South Park had a two-parter set in the future where everyone has become an atheist. However, the atheists have split into three factions (or "organizations"), fighting wars just as bloody as the religious wars of the past, over what their name should be.

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Comic Books

• Artesia has multiple religions (the Old Religion of Yhera, the faith of the Divine King, and the mystery cults, among others), but they all fit into the same cosmology, many gods are worshipped in both religions, and the Phoenix Court of the Empire worships the Divine King but also pays respect to the gods of the Old Religion.

Literature

• Honor Harrington
  • Let's see, we've got the formerly Space Amish Church of Humanity Unchained, with its own internal factions, and its extremist splinter The Faithful, the Methodist-descended Third Stellars(which has practically every congregation (Or even every person) being their own faction), along with a 2nd Reformation Catholic Church, a new Judaism faction, and passing mentions of most other current major religions.

Live Action TV

• Star Trek, which features religious Planet of Hats (Bajor), Outgrown Such Silly Superstitions (while Roddenberry was alive) and religious proliferacy (after he'd passed on)
• Babylon 5: In the episode "The Parliment of Dreams" during a cultural exchange week each of the alien races put on some kind of demonstration of their religion. Every alien species only has one religion, but what will the Earth do? Finally it's Earth's turn.

Cmdr. Sinclair: shaking hands or bowing or giving the appropriate gesture This is Mr. Harris. He's an atheist. Father Cresanti, a Roman Catholic. Mr. Hayakawa, a Zen Buddhist. Mr. Rashid, a Moslem. Mr. Rosenthal, an Orthodox Jew. Running Elk, of the Oglala Sioux faith. Father Papapoulous, a Greek Orthodox. Ogigi-ko, of the Ebo tribe. Machukiak, y Yupik Eskimo. Sawa, of the Jivaro tribe. Isnakuma, a Bantu. Ms. Chang, a Taoist. Mr. Blacksmith, an aborigine. Ms. Yamamoto, a Shinto. Ms. Naijo, a Maori. Mr. Gold, a Hindu. Ms.... Fade to Black

Video Games

• Zig-Zagged with any accurate Historical Strategy game subgenre like Crusader Kings or Europa Universalis series from Paradox games, in general, That can allow you play any nations from any time period that know there a lot historical (or still existed modern) religions (which also included all their historical factions as well) in them to use to make a minority who allowed another religion into majority official religion of that mentioned nation or not until right time and other consequences ensue to prevent them to convert.
• Dragon Age: Origins: more than one religion overall, but you only get one religion per race - there is no sense that any particular person could ever be a different religion from the one they are. The human religion, that of The Maker and the Prophet Andraste has some subdivisions, but these are clearly marked as 'real religion' and 'evil cult' so don't really represent religious diversity. The narrative itself (and the Warden, if you choose) can be read as having a subtle athiestic bias.
  • Notably averted in Orzammar, where you find a dwarf cleric of Andraste who is genuinely good; should you choose to help him, you see why there's only one religion per race.
  • There's also a subversion that gets a bit more attention in Dragon Age II, where the Tevinter Imperium has its own schismatic Chantry that's under the control of the mages, rather than the other way around. Fenris calls it a scam to keep the magisters in power, but we don't actually see the Black Divine or any of his people.
  • Also, if you read the Codex, the reason there's only two versions of the Maker's worship is because the Chantry takes it very seriously, aggressively wiping out variations of the faith. Kind of like the Catholic Church used to, only with more success. It's even part of the religion that the Chant must be recited perfectly, with no variations. However, despite all of this, the occasional underground offshoot manages to thrive.
  • Likewise, it's mentioned that when the Chantry decided to lead an Exalted March against the Dales, the "Canticle of Shartan" was stripped from the Chant of Light, removing all reference to the Dalish General of Andraste's army.
  • It's interesting to note that, apparently as a result of being raised on the surface by exiled nobles from Orzammar, Varric Tethras is ostensibly non-religious, but frequently will invoke both the Dwarven Ancestors and Andraste's name. It is confirmed in Dragon Age: Inquisition that Varric is in fact Andrastian, although he doesn't often bring up the fact that he sincerely believes.
  • Hawke also appears to show acceptance of multiple, diverse faiths. Despite being nominally Andrastian, Hawke nonetheless aids Merrill in performing several Dalish rituals, in Legacy offers a Dwarven prayer after recovering the body of Varric's ancestor in the Deep Roads, works with the Qunari on numerous occasions and in Mark of the Assassin, while also mentioning offhand that their family was one of the few that the Chasind Wilders chose to trade with in Lothering. A Snarky!Hawke gives a few hints that s/he is actually more of a Nay-Theist.
  • While there's one main religion per race, there are some minority faiths and a few converts. In addition to the Andrastian dwarf mentioned above, the Chasind and Avvar barbarians are human polytheists, and there are a fair number of converts to the Qunari faith who are human or (especially) elven. Many of the city elves are Andrastian, though they retain some traditions of elven polytheism (such as the vhenadahl, or sacred tree). The Rivaini are pantheists who believe in a Natural Order (and also have a number of Qunari converts).
• In The Legend of Zelda, the Triforce seems to be used universally and everyone seems to adhere to the same legends, yet each race is mainly seen worshipping deities separate from the Golden Goddesses - usually protector spirits like Jabu-Jabu or Valoo, but other ones as well, like the Ocean King or Hylia or the Desert Colossus. It's possible these all form a unified pantheon hierarchy, but that's never been made explicit.
• The Elder Scrolls plays with it in a number of ways depending on the instance.
  • Averted in general with the primary religion of most of Tamriel, the religion of the 8 (or 9) Divines, sometimes referred to as the Imperial Cult. It was a compromise religion created by Alessia, the first empress of Cyrodiil, to appease the different races with different religious beliefs who made up her empire. While the main sect of the religion is based out of the Imperial City in Cyrodiil and is fairly uniform, there are other versions of it in different provinces. For example, the Altmer still refer to Akatosh by his Aldmeri name of Auriel, and have some very different beliefs about the motive for the creation of the universe. Further, many Nords still refer to the Divines by their ancient Nord names and still hold Shor (aka Lorkhan) as their top god even if the official version of the religion leaves him out.
  • That said, every single religion on Tamriel shares a number of consistent elements in their creation stories. It's usually their interpretation of the motives of the gods involved that differ.
  • For some 4000 years, the Dunmer of Morrowind instead worshiped a trio of Physical Gods known as the Tribunal, or ALMSIVI, made up of Vivec, Almalexia, and Sotha Sil. The Tribunal Temple was founded which worships them. The friction between the Temple and the Imperial Cult is felt in the main quest of Morrowind. Then Subverted within the Tribunal Temple. While they present themselves in this fashion and attempt to suppress all dissent, the Dissident Priests and Nerevarine Cult have split off from the mainstream Tribunal worship. When talking to Vivec, he'll reveal that the Temple isn't entirely right, and that the others aren't completely wrong.
  • Also Averted when the Dunmer Ashlanders are considered. They practice ancestor worship (which is still part of Tribunal Temple doctrine, though to a lesser extent,) and also, to a degree, worship (or at least respect) the Daedra. (Particularly Azura, Boethia, Mephala, Sheogorath, Molag Bal, Mehrunes Dagon, and Malacath.) Again, the Daedra are acknowledged by the Tribunal Temple, but are considered subservient to the Tribunal.
  • Speaking of the Daedra, they are worshiped (usually individually) by many in Tamriel as an alternative to the Aedric Divines.
  • The Skaal of Solstheim add another to the mix, with their worship of the "All Maker."
  • While some Argonians may convert to the religion of the Divines, their species as a whole tends to worship the Hist, a race of sentient trees native to their Black Marsh homeland.
  • The Dark Brotherhood worships Sithis, also known as the "Void" or the primal "Is Not".