Originally created by Hendryk for the Alternate History Tropes section of Tv Tropes, this is the cousin of all similar scales dealing with the scientific “hardness” and “softness” of sci-fi works – of course, in this case, the genre is alternate history instead of science fiction.

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 AlienSpaceBats.

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 technological 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 ooze into a pool. 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 – Nazi Germany’s plan to invade Britain during World War II, which has become Memetic Mutation because of this – to be one of the worst military plans ever conceived (it would have been a catastrophic defeat for Germany that would have effectively destroyed the Wehrmacht and allowed the Allies to win up to a year earlier) – 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”.

Source: wiki.alternatehistory.com