Sliding Scale of Alternate History Plausibility

Like other forms of Speculative Fiction, Alternate History varies in its inherent "hardness" with AH Fandom generally grading it by how "plausible" the AH is based on historical realism and verisimilitude. At the "hard" end of plausibility are well-researched pieces that take into account historical sources and trends, logical changes due to the Butterfly Effect, and try to produce allohistorical events that flow logically from the Point of Departure/Divergence (PoD). At the "soft" end are works of pure Fantasy and Rule of Cool, generally a result of Alien Space Bats.

While the line between "plausible" and not is subjective, the following five levels tend to encompass the general consensus in the online AH Fandom:


 * Type I - Hard Alternate History: These are works that adhere to very strict, even scientific standards in their plausibility. Research is often detailed and intensive, Butterflies are followed logically, and with attention to details, such as the economic or logistical feasibility of an invasion. At their best they set aside the personal "wants" and "if only's" of the author and try to accurately determine the most likely What If result of a PoD. In some cases they are arguably more "plausible" than actual history! A majority of historical counter-factuals fall into this category. Alternate History Wanks very rarely fall into this category. Type I Alternate Histories are often "unsteered", meaning that they have no predetermined outcome and simply follow the logical changes ("what if Lee won at Gettysburg?").


 * Type II - Hard/Soft Alternate History: These are works that incorporate both Hard and Soft elements. Perhaps it is well researched and incorporates historical methodology, but leaves room for adventurous outcomes or Rule of Drama/Cool/Comedy. The author may take some liberties in following butterflies, such as allowing some post-PoD births or a measure of parallelism. Perhaps they've accelerated a certain technology in a way that's rather "convenient", but doesn't strain the Willing Suspension of Disbelief too much. Or perhaps the butterflies and methodology are sound, but obviously "steered" with a predetermined outcome ("I need a setting where an independent Confederate States faces off against the Union in a Great War analog, what PoD can I choose to get there realistically?"). Some counter-factuals may fall into this Type, such as those by historians with an obvious political bias or pet theory or ones that allow an improbable outcome to look at the ramifications in order to study a tangential area (for example allow for an "improbable" Japanese WWII victory scenario in order to study the cultural implications of such an event). A well-done Alternate History Wank can qualify here.


 * Type III - Soft Alternate History: These are works where the plausibility of the setting's alt-history is less important than setting up a world that fits the creator's artistic objectives. Research is often minimal to moderate and used simply to give some verisimilitude to the setting. Butterflies may be utterly ignored, Politically-Correct History may make an appearance, and plausibility will take a back seat to Rule of Drama/Cool/Comedy. Perhaps parallelism has run to ridiculous levels or the author uses Historical Domain characters born way after the PoD ("I don't care if he was born centuries after the historical Fall of Rome, I want General Patton fighting the Modern Romans in Gaul!"). Perhaps the rate of technology growth is just too high. Perhaps the author's politics and desires so totally tint the work that it breaks any Willing Suspension of Disbelief and turns it into an AH-themed Author Tract. Many Alternate History Wanks fall into this Type. Type III Alternate Histories are almost always "steered" ("okay, so I need a Confederate George Patton running a Blitzkrieg through Stalinist China...").


 * Type IV - Utterly Implausible AH: These are works that are so Soft that they melt. Works that are so implausible as to be effectively impossible and so Soft as to prove impossible to take seriously. Works where research was so poor or ill-considered, author politics so prevalent, Butterflies so ignored, details (logistics, politics, etc.) so overlooked, often purposefully, that there's no way anyone with even a passing familiarity with the history can take it seriously. Infamously implausible scenarios like Operation Sealion are often placed here, as are utterly implausible technology jumps, such as Aztecs developing breech loading rifles in 1420. Over-the-top totally ludicrous Alternate History Wanks are usually put here. Obviously a lot of YMMV here. One good "rule of thumb" is if a PoD necessary to make the outcome plausibly happen is so far in the past that Butterflies would totally negate the very events that created the setting (such as a PoD to give Hitler the fleet he needed to invade the UK would need to be before WWI, probably negating the rise of Nazism), then it may be a Type IV. Note: These works are often defined as Alien Space Bats; in fact the original term "Alien Space Bats" was coined to refer to these type of implausible works!


 * Type X - Alien Space Bats and Fantastical AH: In contrast with Type IV, these works are deliberately designed as pure fantasy, typically following the Rule of Cool. Some sort of Applied Phlebotinum or Sufficiently Advanced Aliens or Negative Space Wedgie or blatant magic causes a PoD that completely changes everything. What If aliens invade Earth during World War II? What if time traveling modern Cherokee give assault rifles to their distant ancestors in 1820? What if the modern island of Manhattan was time-ported to the Mediterranean in Roman times? A sub-type of this rewrites actual history in fantastic terms: what if George Washington's army used nature magic to fight necromantic redcoats? Ironically, many Type X works can become very "Hard" following an initial fantastical PoD, diligently using historical research and Butterflies to see what would logically happen if the Cherokees really did have Kalashnikov assault rifles in 1820. Type X works can be "steered" or "unsteered". Note to Tropers: when posting examples please make a note on how "Hard" the work is after the initial PoD if the PoD is the ASB element; for example "after the Negative Space Wedgie moves Manhattan, the rest of the work follows a more Type II or even Type I level of plausibility".

Needless to say, the line between the different Types is highly subjective, often depending on an individual's personal interpretations or what historical theory he/she believes. Where history is vague (such as Prehistory) pure creative writing or blatant Ass Pulls might be used. The perception of Type II vs. Type III vs. Type IV in particular can be very much in the eye of the beholder. Furthermore, perceived extreme cases of implausibility in a Type III can lead to cries of ASB ("and what magical fairy gave the Japanese the cargo ships they would have needed to invade Hawaii ?")

Also, technology can be a source of debate: is Steampunk a Type III or IV or even X? How realistic is Airship passenger travel in the year 2001 anyway? Politics enters in as well, with steered AH used to create a Utopia based on the creator's personal political/economic views or conversely a Dystopia based on opposing views.

Note that Geological PoDs should be rated by the plausibility of the event. The Iceland volcano erupting ten years earlier is very plausible (probably Type I) while the existence of Atlantis (geologically impossible) is ASB (Type X). Weather PoDs are harder to gauge considering the unpredictability of the weather and its far-reaching effects, and thus more debatable.

Note also that none of these types are inherently superior or inferior to the others and all can be used effectively depending on the purpose to which they are being put and the story being told; a Type 1 might be more a plausible examination of the history than a Type IV, but a Type IV might conceivably, despite it's issues with historical credibility, be a better or more entertaining story than a Type 1.

Type I : Hard Alternate History

 * The What If? series of books where professional historians analyze some counter-factual scenarios (though there are some fans who question their conclusions, placing some contributions arguably in Type II).
 * For Want of a Nail by Robert Sobel: a very detailed and carefully researched novel that explores the "history" of a world where the Continental Army lost at Saratoga.
 * How Few Remain: The first book in Turtledove's Timeline-191 series explores a vividly realistic 19th century following a southern victory in the American Civil War.
 * The Yiddish Policemen's Union by Michael Chabon. On the Soft side of Type I, but still very well put together.
 * The Iron Dream by Norman Spinrad where Adolf Hitler emigrates to the USA and becomes a Science Fiction author rather than enter politics. Intended as an Anvilicious satire of perceived fascist trends in Speculative Fiction at the time, it still manages to be a plausible AH story.
 * Eric Flint's Trail of Glory series starts off with an arrow that hit Sam Houston being a minor injury instead of the major one it was in Real Life, and follows through from there.
 * Jared's Decades of Darkness hyper-detailed AH which diverges due to Thomas Jefferson dying of a heart attack in 1808. New England secedes and the US becomes a hyper-expansionist slaveocracy. There is a very loose overall direction to the timeline ("make something like the Draka series, only plausible") but this is decidedly secondary to the "POD, then events follow" approach.
 * Lighter Than A Feather by David Westheimer. The US carries out Operation Olympic and invades Kyushu in 1945. Mostly presented as a series of vignettes evenly divided between US and Japanese, the book also sets out in some detail the general course of the invasion. The Japanese are more than just cartoonish buffoons to be mown down, and come arcoss (to this troper, at least) as thoroughly rounded and interesting characters representative of the time, further pushing it into Type I territory.
 * Thande's Look to the West (though there is something of a background artistic 'theme' which sometimes leads it to dip into Type II).
 * The online 1983: Doomsday takes its POD from a real-world event - a false nuclear launch alert in Russia that could have turned into a full-blown nuclear exchange. In this timeline, it does. The timeline's authors allow for some play, making it a soft Type I, but work hard to keep things relatively authentic (any "real world" people presented as surviving Doomsday must have been verified as being in an unaffected area. For instance, Barack Obama was a student at Columbia in September 1983, and was almost assuredly killed when NYC was obliterated, but George W. Bush was in rural Texas and survived.)
 * In one particularly interesting case, authors discovered that John F. Kennedy, Jr. was actually in India on the projected POD, and would have survived, becoming an important figure in the new timeline.

Type II : Hard/Soft Alternate History

 * The Great War trilogy from Turtledove's Timeline-191 series (the sequel to How Few Remain). We see some Hard aspects (political Butterflies, Expys of post-PoD famous people rather than straight appearances) and some Soft elements (European politics and history totally unaffected by the huge divergence in North American events).
 * The Moscow Option by David Downing. Seems to have started with Downing wanting to find a way to have the Axis come as close to winning the war as possible, but still lose. To have them outperform their counterparts he usually engages in very realistic Type I style events, all propogating from two changes, one relating to Germany (Hitler is incapacitated for a time and stops interfering with his generals) and one to Japan (they realize the US has broken their code and create a new plan for Midway that exploits this fact), but the success of Germany in particular really stretches their logistical capacity and reserves to unlikely amounts - but it's still enough to be historically plausible even though it isn't the most likely result.
 * Pretty much everything by Robert Conroy
 * The Lion's Heart duology by Steven Barnes. An inversion of historical European dominance and enslavement of Africans creating a world where African Masters keep European slaves on North American plantations. Pretty much every culture that "Cryptohistory" assumes could have colonized America does (note: in reality most of them couldn't or wouldn't have even with the novels' Butterflies), but does show some Hard allohistorical trends and Butterflies. Also Both Christianity and islam exist even though the POD is well before the birth of Jesus.
 * Geologic PoD example: Turtledove's (again) Down in the Bottomlands where the Mediterranean sea is dry desert. Geologically plausible since it happened periodically in history Major climactic and cultural butterflies, including the continued existence of Neanderthal Man. Arguably Type I.
 * Robert Graves' historical fiction fit firmly into this category. They are extremely well researched but he willfully changes or distorts events and personalities to tell the story he wishes to tell. Fact and Fiction are often so well blended, especially in regard to events(far less so with characterization) that you pretty much have to be an expert in the subject matter to tell the two apart or to know that events that went a, b, c, d in real life go b, d, a, c in the novel.
 * Iskriget by Anders Blixt. This espionage adventure mixes hard sociology (by creating a credible alternative 20th century in which Britain had failed to reach ascendancy in the 18th century) by a Rule of Cool approach to technology (Studio Ghibli-style cloudships and ice juggernauts) and geography (Antarctica and Australia are replaced by two more pulpish continents). However, the author's 1940s approach to racism and sexism is strictly Type I, the protagonist being a well-educated Euro-Indian man who encounters a lot of prejudice.
 * World E4 in Ian McDonald]'s Planesrunner in which 9/11 didn't happen, Al Gore ran in 2004 and won. The only thing that keeps it from being Type 1 is an unexplained "something" that happened to the moon.

Type III: Soft Alternate History

 * The latter books of Harry Turtledove's Timeline-191, where In Spite of a Nail really sets in, historical characters multiply (Churchill, Patton, etc.) and the historical parallelism strains some reader's suspension of disbelief.
 * Journey to Fusang by William Sanders: Rule of Cool and Rule of Funny AH Picaresque whose historical liberties are notable. Another "everyone that Cryptohistory assumes could have colonized America does" setting. Every Historical Domain Character has dodged the Butterfly of Doom. Arguably a Soft Type II, and when written probably would have been considered one, but the science of history marched on.
 * Years of Rice and Salt by Kim Stanley Robinson. The bubonic plague kills 90% of all European life, conveniently not moving into North Africa or the Middle East despite intricate trade networks at the time, and somehow not burning itself out before mass death (as plagues which fail to leave at least some people alive to be carriers tend to do). Also severe In Spite of a Nail: the Yongle Emperor of China and Tokegawa Shogunate of Japan still rise despite a PoD centuries earlier. There's also an ASB element in the "Bardo" framing story. Considering how well written it is, many find the MST3K Mantra applies. Arguably a Type II or IV, depending on your Butterfly Effect interpretations.
 * The first point may or may not be explained by the generally higher hygienic standards in the Islamic world at the time - better hygiene, less rats, less fleas. The second one, however...
 * Actually, North Africa was pretty thoroughly Muslim in that period, as it largely remains. Spain was conquered by way of Morocco before the Middle Ages even properly began, let alone the plague hitting. So it was in fact an important part of the Muslim world. Which got pretty whacked by the Black Death in actual history, as did China under the 'Pax Mongolica.' Its social consequences just weren't as dire.
 * S.M. Stirling's Draka series, where a Social Darwinist South African slave-based superpower emerges and eventually . Many in the AH community find the history implausible, though it remains one of the modern classics of AH. Arguably a Type IV.
 * Harry Harrison's Stars and Stripes trilogy in which Britain allies with the Confederacy during the American Civil War. Begins as Type II but jumps into Type III territory when an accidental attack on a Confederate stronghold leads to Britain going to war with the Confederates and both North and South siding together against the common enemy: Britain.
 * Covert Front takes place in an alternate 1904 where World War I is already taking place. That's pretty much all we're given, and it's all we really need for Mateusz Skutnik to tell a good spy story.
 * While Fyodor Berezin's Red Stars duology involves travel between parallel worlds, a huge part of it is devoted to the divergence of the other world from ours, so those sections can rightly be called Alternate History. The author uses the common belief that Stalin had always planned to betray Hitler, but that Hitler simply beat him to the punch (i.e. both sides were ready to attack but were unprepared to defend). Thanks to British interference during Nazi Germany's invasion of Southern Europe, he delays Operation Barbarossa (the invasion of the Soviet Union) by a month, giving Stalin plenty of time to enact his own invasion plan. The USSR invades Germany in 1941. Despite being unprepared, Germany still holds out for almost two years, but is ultimately beaten. The Red Army proceeds to take Italy and "liberate" France, stopping just short of crossing the English Channel. Realizing their new rival is the US, the Soviets make sure (through sabotage and covert aid to Japan) that America is tied up with the Pacific War. The Domino Theory then ensures that all of Europe, Asia, Africa, and, eventually, Australia go communist, leading to a Not So Cold War between USSR and US, with the former being the dominant power. Oh, and democracy doesn't exist anymore, as the constant red threat forces the US to institute martial law.
 * While this may seem like a Mary Suetopia, the author makes it abundantly clear that the other is a Crapsack World, where the two superpowers no longer hold back on nuclear weapons and constantly engage in massive battles in the oceans. The ending, however, is highly controvercial:.
 * Kathleen Anne Goonan's In War Times and it's sequel in which time travelers arrange for FDR to live long enough for a ffth term during which he apparently acquires a certain other wheelchairbound man's mental powers because he persuades Stalin to give back the Eastern European nations back their freedom and not divide Germany into East and West. Then Truman manages to get a Civil Rights Act passed in 1950 which would have required the cooperation of Congress (unlike his desegregation of the armed forces). And then they prevent the assassination of JFK after which nothing bad ever happens again.
 * Children Of The Revolution, an Australian film about the hypothetical son of Josef Stalin and his rise to political power very nearly resulting in a communist revolution in Australia. Rule of Funny is strictly in charge for most of the film.
 * World E3 in Ian McDonald's Planesrunner in which everything is coal powered because there's no oil and the steam engine was never invented because the electric motor was invented first.
 * The Star Trek: The Original Series episode "The City on the Edge of Forever," where Kirk and Spock going back in time and keeping one particular pacifist activist from dying somehow causes the Nazis to win WWII, because her activism keeps the U.S. out of the war until it's too late. The fact is that that was exactly what really happened; strong, organized pacifist and isolationist movements were very influential over the American public and many American politicians in the early years of WWII, which is why it took an Axis attack on American soil to get the U.S. to enter the war. But all the pacifist speeches in the world weren't going to make any difference after Pearl Harbor.

Literature

 * Another Turtledove Geologic example: The Atlantis series, where the North American east coast is a large island. While geologically somewhat plausible the PoD could arguably Butterfly the existence of Humans. Plus the implausible parallelism of the history itself.
 * Turtledove's Days of Infamy; Japan invading Hawaii (considered logistically impossible) pushes this story to Type IV in many minds.
 * World E2 in Ian McDonald's Planesrunner in which Great Britain is a Muslim nation, having been colonized and converted during Islam's great wave of expansion. Plausible enough by itself but what puts it in Type IV territory is the reason: Great Britain, instead of being located north of continental Europe is located a hundred miles west of the Straits of Gibraltar. And Ireland didn't go with it.

Live-Action TV

 * Spike TV's "Alternate History" special. With a point of divergence that starts with a successful repelling of the Normandy invasion due to an unexplained influx of jet aircraft on the German side, Nazi Germany manages to completely turn the tide of the war, and conquer both the United Kingdom and the United States. The Soviet Union also doesn't seem to exist in this timeline.

Type X : Alien Space Bats Alternate History

 * The 2006 mockumentary CSA: Confederate States of America, where the South not only wins but takes over the whole of the Union! Few take the history seriously, including the creator himself, since it was designed as a Satire of race relations in the US rather than an accurate counter-factual representation of a southern victory world.
 * Another obligatory Harry Turtledove example: the Worldwar series. Lizards from Outer Space invade during World War 2 and the Axis and Allies must set aside their differences to save Earth from alien conquest! Interestingly quite Hard AH after that, at least in the first books (Type I or II), but like many Turtledove works starts to Soften as the series advances to the point of being Type III to IV by the last books).
 * The Guns of the South by Guess Who: Time traveling South African Neo-Nazis bring Robert E. Lee's army AK-47 assault rifles. Only a stand-alone book (so it's hard to predict long-term trends), but seems to go Type I after the PoD.
 * S.M. Stirling's Island in The Sea of Time series, wherein the contemporary island of Nantucket is time-ported back to the Bronze Age. Somewhat Soft after the PoD (Type II) as like most of Stirling's work it follows Rule of Cool.
 * Eric Flint's Ring Of Fire series where a West Virginia coal town is time-and-space-ported to Germany in the middle of the 30 Years War. Very meticulously Hard after the PoD (Type I).
 * Heirs of Alexandria by Mercedes Lackey, Eric Flint, and Dave Freer, but due to the large scale of the change, introducing magic, and how long ago it happened, probably a type II (Hard/Soft Alternate History) when the series start, mainly due to good research.
 * The Tales of Alvin Maker by Orson Scott Card: A retelling of the story of Mormonism founder Joseph Smith in a North America Mirror Universe where magic is real.
 * The Strangerverse on AlternateHistory.com is a loosely-tied saga, whose common tie being a time traveler returning to some point (and figure) in the past. To stop his crapsack-apocalyptic future from happening, the Stranger leaves behind tools to aid his "chosen." This generally results in epic nation-wanks. The stories themselves become Type II or III after the "event," depending on the author. Notables include The Britwank Empire and The United States of Ameriwank.
 * Temeraire is the Napoleonic Wars... ! Otherwise a Type II: The society is still reminiscent of the equivalent time period and technologies are much the same, though there are some significant political deviations. (The Incas were never conquered because they also had dragons, for instance).
 * The Ciem Webcomic Series postulates that Boonville, Indiana is overtaken by aliens who are obsessed with engineering monsters for political gain. It is attacked by the National Guard and the town of Gerosha is built in its place - so-named after a seashell with a letter "G" carved into it that was found on a beach in Florida. After that, the growing feud between Gerosha's founding Flippo family and the Hebbleskin Crime Family results in more monsters, more explosions, and even a radioactive MacGuffin or two. Since it aims to become a comic book film, it's very steered and doesn't seem to care about how hard or soft the AH is.
 * Red Alert seems to be Type X-IV. It starts with Einstein building a Time Machine and going back to kill Hitler. Dirty Communists led by Stalin invade Europe with Tesla coils and superheavy tanks. America Wins the War - but some thirty years later, we have a second Soviet invasion of USA... with giant battlesquids, Weather Control Machines, tanks masquerading as trees, Frickin Prismatic Beams, Cloning Blues, Teleporters and Transporters,  bomber blimps, Mind-Controlling soldiers and psychic possession via telephone, all served with a side order of Ham and Cheese. And then, when it seemed it was over, Red Alert 3 comes-a-knockin'...
 * The West of Eden trilogy is probably an X-III, with the fantastic element being that the dinosaurs were never wiped out. Realistically speaking, the extinction of the dinosaurs is probably what allowed mammals to gain dominance and thus humans to come to be, but of course in that case the humans versus lizard-women plot couldn't happen.
 * In John Birmingham's novel Without Warning, a Colony Drop of a mysterious energy field called the Wave wipes out all human life in most of the continental United States and much of Canada, Mexico and Cuba in 2003 just before the invasion of Iraq but after that it's pretty much a Type I including Sadaam Hussein's reaction to "the Great Satan" gettiing it's legs chopped out from under it and what springs from that.
 * Leviathan, by Scott Westerfeld. Darwin discovers DNA and genetic engineering, all before the discovery of x-ray crystallography, PCR, plasmids, or anything else that could possibly allow such a thing. On top of that, apparently DNA from any animal can be combined with DNA from any other animal without any viability issues.
 * Watchmen becomes a type X because of the existence of Dr. Manhattan, but is a Type III otherwise (the non-super powered superheroes have some smaller impacts on the history of fashion and pop-culture of the 20. century). And the primary goal is a total Deconstruction of the superhero genre, not exploring alternate histories.
 * Sky Captain and The World of Tomorrow, a combination of Dieselpunk and Steampunk in an alternate 1930's setting. Involves giant robots and intelligent flying machines.
 * GURPS Infinite Worlds offers the United States Of Lizardia - A world, very much like our own circa 1994, but populated by an evolved species of dinosaur rather than humanity. Beyond Type X, it's also very much Type IV. It being Type IV is heavily lampshade hung - The best guess for how it could possibly exist by the people who in the Infinite Worlds setting study alternate worlds is basically a God with a cruel sense of humor pranking people who study alternate worlds.
 * Fullmetal Alchemist takes place in an alternate early 20th century with working Magitek in the form of alchemy. However, it explicitly takes place in an alternate world separate from our own.
 * The setting of Sergey Lukyanenko's Seekers of the Sky duology diverges from ours when Jesus is killed during the Massacre of the Innocents, resulting in a different Messiah with different powers and goals. Unlike Jesus, the Redeemer passes his one miracle to his disciples, and it spreads from them throughout the world. This miracle is the Word, allowing the user to place any inanimate object into another dimension known as the Cold to be retrieved later. Not only has the Word changed how many things are done in the world (those who possess it keep all their valuables in the Cold), but the Redeemer attempted to end war on Earth by removing all the iron he knew about when he left. Thus, this setting is largely shaped by a major deficit of this very useful metal (e.g. iron replaces gold as currency and status symbol). The duology mostly serves for the author to explore the dominant religion of this world, which is similar to Christianity in some respects but very different in others.
 * Fenspace seems to be Type X-II. It takes place in a timeline where a substance called handwavium was discovered (or set loose) in the early 2000s.  When applied to "ordinary" technology, handwavium "uplifts" it into quirky ultratech, which basically allows anyone to turn cars into spacecraft and pocket calculators into AI supercomputers.  Once this prompts the wholesale exodus of North American Science Fiction fandom into space, the subsequent scientific, social, political and military ramifications are explored with reasonable rigor and an eye toward plausibility.
 * The native superhero setting for GURPS, the world of the International Super Teams, is X-III, perhaps X-II if you're feeling generous. The divergence point is the genetic manipulation of humanity's ancestors millions of years before the present day, but it's only in 1929 that it makes a difference, spawning a world of superheroes and superscience that manages to balance gritty with four-color.  Politics, society, science and technology are all affected realistically by the presence of superhumans in the world.