The terms reference Sherlock Holmes: Watsonian commentary relates to Dr. Watson, Holmes' friend and supposed chronicler of his adventures in-universe, while Doylist commentary relates to Arthur Conan Doyle, the Real Life author of the Holmes stories. They seem to have originated (or at least been popularized) on the Lois McMaster Bujold fan mailing list.
Watsonian or in-universe commentary restricts itself to making statements that are sensible within the story's reality. Watsonian explanations are things like "Character X was lying", "He had plastic surgery over the summer", and "The main character fell off a cliff". A more precise technical term for this is intradiegetic. Tropes which take a generally Watsonian perspective include:
- Anthropic Principle
- Author's Saving Throw
- Some forms of Death of the Author
- Fan Wank
- Fridge Brilliance
- Fridge Horror
- Hand Wave
- Justified Trope
- The many justifications that follow Headscratchers.
- Wild Mass Guessing
Doylist or out-of-universe commentary considers the work as a created object, and prefers explanations based on the real-world motivations or circumstances of the creators. Doylist explanations are things like "The author had a better idea", "The actor died, so they had to hire a new one", and "The author got sick of writing those books, so he killed off the main character". A technical term for this is extradiegetic. Doylist tropes include:
- Author Existence Failure
- Artistic License and all of its subtropes
- The Character Died with Him
- Depending on the Writer
- Forgot About His Powers
- Idiot Ball and all its subtropes
- The Law of Conservation of Detail
- The Other Darrin
- Pandering to the Base and all of its subtropes.
- Plot Hole
- Real Life Writes the Plot and all of its subtropes
- Rule of Index and all its subtropes
- Executive Meddling
- Enforced Trope
A modern example might be the proliferation of Rubber-Forehead Aliens in Star Trek. It is revealed in a Star Trek: The Next Generation episode that an ancient humanoid race "seeded" the galaxy with their genes, thereby causing humanoid intelligent life to evolve independently throughout the Milky Way. This is the Watsonian explanation. The Doylist explanation is that Rubber-Forehead Aliens are cheap to produce, require relatively little imagination, allow the audience to easily read the emotions of alien characters, etc. (And budget was always a concern for Star Trek; when Klingons first exhibited the Rubber-Forehead Aliens trope it was an improvement on their previous make-up!)
Consistency plays a major role in whether a trope is Watsonian or Doylist. By default, Watsonian tropes are defined by Internal Consistency, and are susceptible to Excess of Internal Consistency in the hands of an author that doesn't know how to restrict information to focus on the narrative. Meanwhile, Doylist tropes are defined by External and Genre Consistency, and could suffer from Lack of Internal Consistency if the author doesn't have the ability (either by Executive Meddling or their own writing skills) to address the narrative oddities in their work. Tropes Are Tools, and neither explanation is more preferable than the other.
When Playing with a Trope, note that sometimes a Doylist explanation is interjected purposely into a narrative; for example, in Monty Python and the Holy Grail the Knights of the Round Table (or what is left of them) are chased by the Legendary Black Beast of "AAAAAAAARGH" in the common surreal Terry Gilliam style transitional animation, and are eventually cornered with no chance to escape. What saves them? The animator suffers from a fatal heart attack. Series with No Fourth Wall or as little of one as possible exaggerate this line of thought so that the Doylist answer is the Watsonian one; The Unbelievable Gwenpool has its star try to make herself important enough because she knows that she'd otherwise either be doomed to Comic-Book Limbo or become C-List Fodder for her out-of-universe writers. On a less absurdist note, Direct Line to the Author is a way of smuggling Doylist explanations into a Watsonian paradigm by introducing a fictional author. And finally, most creators don't stick to strictly one interpretation, as the pagequotes from PTerry suggest.
Conversely, some authors acknowledge that they don't have complete hold over the characters they've created and allow them to operate on their own logic - which is an example of Watsonian perspective influencing Doylist one.
In the German-speaking fandom of the Disney Ducks Comic Universe, the two ways of analyzing the stories are called Donaldismus literaricus (which treats the work of Carl Barks and others as works of art and literature) and Donaldismus archaeologicus (which treats them as factual reports from the Earth-like planet called Stella Anatium - the Star of the Ducks). In the D.O.N.A.L.D. (Deutsche Organisation Nichtkommerzieller Anhänger des lauteren Donaldismus = German Organization of Non-Commercial Adherents of True Donaldism) the latter tends to dominate. Donald Duck comics are Serious Business, definitely.