SF writer Poul Anderson called this an "idiot lecture", in the sense that either the lecturer must be an idiot, or the lecturer must think the lecturee is an idiot. Nevertheless Anderson used the device often at the beginning of short stories, usually to establish historical details when an operative was briefed by a superior. Lampshaded at least once via the lecturee thinking to himself "He must think I'm an idiot!" and similar. In more than one Anderson story, such a speech is delivered to an enemy and reveals something that really ought not to be revealed to an enemy ("and that's why we 'elves' can't stand iron"), followed by "added hastily" in a blatant (yet always successful) attempt to distract from said revelation.
Foundation Series' "The Merchant Princes": Trader Mallow and his friend, the retired Trader Jaim Twer, discuss an upcoming Seldon crisis. As Seldon and his Plan is a required part of a lay education on Terminus, the fact that Mallow had to explain it to his "friend" helped him deduce that Twer had been trained as a priest, not a layman, and is working for Jorane Sutt.
"Risk": The reporter, Nigel Ronson, describes to Black three people that he already knows, in rather unflattering tones. General Kallner is a military idiot, Dr Calvin is so aloof that she could travel through the sun and come out frozen in ice, and Director Schloss is too egotistical to give a decent answer to his questions. It works to summarize the people if the audience hadn't read "Little Lost Robot".
"Runaround": When trying to figure out what went wrong with their robot, Donovan and Powell review the situation they're in, which Dr Asimov uses as an opportunity for Exposition about the three Rules of Robotics.
Methuselah's Children opens with a meeting of Howard Foundation members where one character goes on for several pages, detailing the history of the foundation, its goals, and his plans for the future. While very interesting (to the reader), the entire monologue is framed as an As You Know. As the characters are all extremely long-lived and therefore very patient, they don't mind too much. He is however called on it by Lazarus Long, who has better things to do - mostly involving sex.
Inverted in Starship Troopers. It's used toward the reader as an excuse to skip exposition. Specifically, Rico's narration skips over a lot about the powered armor by telling the reader "But if you really are interested in the prints and stereos and schematics of a suit's physiology, you can find most of it, the unclassified part, in any fairly large public library." On the other hand in the Action Prologue their sergeant goes over the plan of attack even though it's been hypnotically implanted in the troopers, as "some of you don't have minds to hypnotise."
One of H. P. Lovecraft's literary quirks was his extreme aversion to writing dialogue. Thus, when he absolutely had to write about two characters talking, he instead only wrote one person's lines, which inevitably contained all the content of the other party's responses, as well.
Novelist Harry Turtledove has a tendency to fall into this trap in his multi-volume alternative history epics (such as the Worldwar and Timeline-191 series); he will often recap complicated alternative histories and the plots of two, three or more previous novels in the series by having characters engage in conversations or think to themselves about things that they would already know.
By Work
In Nineteen Eighty-Four, Orwell uses the very clever trick of getting the basic facts explained to us by the secret book of the Brotherhood, which works as a subversive primer to the indoctrinated population. We learn later on that the Brotherhood and the Inner Party are the same, so everything in the book could be wrong too...
A lot of exposition in the Alexis Carew series is done by having people explain things to the protagonist. Justified since Alexis grew up on a backwater colony world and until joining the New London Royal Navy had cared more about crop prices and farming and logging techniques than about space travel and international politics and history.
In Animorphs, the first chapter is usually dedicated to the Rotating Protagonist explaining the series' concept (the Earth is being invaded by Puppeteer Parasites, they turn into animals to fight them, etc.) Clearly this is being done for people who picked up the books out of order, but by the last few entries the narrators start throwing in "but you know this already."
Area 51: In several cases necessary information is given to the reader by repeating things characters already know. Sometimes it's lampshaded, such as Mualama's nephew Lago (whom he does this with) feeling annoyed that he's getting another lecture on things he's aware of (his uncle is a professor). Mostly though it's given by other means, such as briefings or discoveries conveyed to characters that didn't know about it.
The Assassins of Tamurin: S.D. Towers fills the reader in on the entire Backstory of the Empire of Durdane by devoting most of a chapter to covering a History class.
In The Bad Guys book "The Furball Strikes Back", Mr. Wolf explains the plan to stop the bulldozers threatening to destroy the forest, much to the annoyance of Mr. Snake, who knows the plan already, as Mr. Wolf has been repeating it over and over. Turns out, he's been repeating it because Mr. Shark keeps forgetting key details about it.
Before They Are Hanged includes an early briefing for military officers ending, "That fortress, as we all know, is already in the hands of the enemy." This is an aversion, as the officers in question are useless nobles who have only the faintest grasp of the war. The briefing officer is a commoner who rose through the ranks and has enough sense not to say, "as you ought to know."
The Belgariad: Early on, King Fulrach informs Belgarath the Sorcerer and Polgara the Sorceress of the plot-inciting crisis they're already investigating, peppered with several repetitions of "You know this"; thanks to Exact Eavesdropping, this is also how the protagonist learns who his "Aunt Pol" and "Mister Wolf" truly are. It's Justified because Fulrach also has the unenviable job of telling them that the other monarchs have summoned them for an audience due to the crisis, and is trying to placate them.
Cantata in Coral and Ivory: Subverted by the narrator Deule, who prefaces some of his exposition this way. He's actually presenting new information to the person he's talking to, but it would be improper for Deule to admit that his new lord doesn't know something he should.
In Childhood's End by Arthur C. Clarke, the character Jan Rodricks explains the theory of relativity to his sister in a very long letter, which she should already know, seeing as how this was a highly scientifically advanced society, almost to the point of dystopia.
Dicken's A Christmas Carol and any parody/homages to it. Because of the time travel aspect of voyeuring into people's lives it somewhat requires them to explain the situation to each other in order to further the plot.
Clan of the Cave Bear: Broud, the newly selected leader, calls a meeting of the Clan, and begins by stating, "As you know, I am now your leader." This causes the clan members to exchange puzzled looks, since they obviously did know.
The fundamentals of furycrafting are presented by Tavi to Max as if it's a necessary refresher because he's such a bad student.
The author has noted that there were some significant bits of backstory and world-building that he ended up leaving out or delaying in order to avoid slipping into this trope. He took four books to explain that "-ar" at the end of someone's surname name meant they were illegitimate, and never got round to explaining that the line of Gaius had restarted at "Primus" dozens of times in the past (with Gaius Sextus being the fourth First Lord with that name) because all of the viewpoint characters would have already known all about it from basic history classes.
Used to lead off the briefing on the VX nerve gas at the beginning of A Deeper Blue. Given a Lampshade Hanging a few paragraphs later with the acknowledgement of the speaker that he's covering old ground for those at the briefing.
In Destined to Lead book 2, Healing, Resurge, the Proud Warrior Race guy uses this trope to explain why he knows who on Mysterium 'Gakkar' is, and by extension the giant stone golem they are conversing with.
Played with in The Science of Discworld, where Ponder, speaking to the senior wizards, precedes his explanation of fundamental Discworld physics with "As I'm sure you know", but only out of politeness. A footnote explains that what he actually means is "I'm not sure you know this..."
Justified again in the third Science book, when Ponder's reports on the situation go ignored and he has to explain himself all over again on the spot, using this trope to let his colleagues save face.
Wintersmith: Tiffany ends up having to do this to Know-Nothing Know-It-All Anagramma, because just asking her to show you how to do something just results in a lot of stalling until she says she has a migraine.
Doon is a Parody of Dune, which, as noted below, is notorious for its volumes of As You Know. The parody reflects this.
"Come, come , Peter," the Baron chid. "Surely there is no flaw in my plan. Review it for the benefit of this lad, Filp-Rotha, my nephew — I being, in fact, his uncle, the Baron Vladimir Hardchargin, who is who I, myself, am."
Dragonlance: The New Adventures: The first book is prone to this, with Elidor explaining the different subraces of elves and Sindri the different schools of wizardry. Justified since Nearra is an Amnesiac Hero.
Dune is as appallingly loaded with As You Know as any book ever written.
The chapter where the villain first appears consists entirely of As You Know dialogue, complete with having the villain introduce himself to his chief henchman: "Is it not a magnificent thing that I, the Baron Vladimir Harkonnen, do?" Justified by Baron Harkonnen being so fond of describing plans that at one point he himself admits to it being a flaw.
"The Spice must flow!" (Usually accompanied by a summary of its multipurpose nature.)
Played with during the last part of George Stewart's Earth Abides. The protagonist, Ish, is now an old man, spending most of his time in a mental fog, cared for by others. When this fog lifts, Ish discusses the current state of the Tribe with Jack, his great-grandson and caretaker. Almost every answer Jack offers is punctuated with, "...as you yourself well know, Ish," even though Ish is, at this point, as clueless as the reader.
In The Famous Five book Five on Kirrin Island Again, Dick finds out that Mr Curton is a journalist, and tells Anne that it means somebody who writes for newspapers.
Justified in Fitzpatrick's War as the general history of how the world turned into a post-apocalyptic steampunk Neo-British Empire-dominated dystopia is recited in a verbal exam by the novel's protagonist, Robert Mayfair Bruce. Coincidentally, Bruce was shocked to have gotten such an easy topic.
An early scene in The Fold shows the teleportation project team in front of the oversight board that decides whether they'll get an extension on their research grant. The occasion is used to walk the audience through the theory and past few years of work for the project, despite the fact that the oversight board should know all this from previous meetings. Further, the board is surprised when the project lead points out that their years-old contract keeps all data and documentation subject to the team's discretion.
In the novel Frankenstein, the title character receives a letter from his adopted sister which tells him his own life story in nauseating detail. The phrase "You will recall..." pops up a few times. Likewise there's one that begins along the lines of, "I'm sure you remember our young maid, Justine, but in case you don't..."
The Narrator of Julian Comstock leaves a footnote apologizing for explaining events that his reader is likely to be familiar with, but says he's also writing for the benefit of any foreigners who might read it, or readers in the far future. In-Universe the class-divided nature of American society means that things often have to be explained; for instance, the title character explains the cause of the war in Labrador to soldiers from the landless classes who are illiterate and therefore don't read newspapers.
James Hogan rather neatly avoids this trope while still managing to do huge Infodumps in his Ganymede series, by managing things so that there's always someone present who justifiably needs the infodump, whether it's a biologist getting briefed on extremely advanced physics, a physicist being brought up to speed on political matters, or a businessman being briefed on the fine points of biochemistry. It helps that Hogan's got a huge multi-disciplinary team to work with, and better, the main character is a man whose biggest talent is his ability to cross-correlate information from many areas without being a specialist in any of them himself. This means he often specifically requests an infodump from a specialist.
Done in the first chapter of The Great Pacific War. The Japanese cabinet meets to discuss the dangerous riots and the seeds of revolt that are gaining strength, and the Premier opens by saying "As you know, our country is experiencing dangerous riots, and the revolts are gaining in strength."
At the very beginning of Harry Potter and the Philosopher's Stone, Dumbledore and McGonagall have a discussion about things each one of them knows in detail. Of special mention are the specifics of the war they have just been fighting, the introduction of the villain's name, which has a vague justification, and telling Dumbledore he's noble, just to establish him as a good guy in the books. Also, they refer to each other by last names, while they are on first-name terms in later books and have known each other for decades. The scene with Dumbledore and McGonagall is mostly gratuitous, in that most relevant details in that scene are also covered later, being told to Harry directly; and it refers to a lot of things that aren't apparent until later books, like Sirius Black.
This also shows up in a peculiar form (you might call it an inversion) partway through Philosopher's Stone, when Hermione is telling Ron and Harry about the Philosopher's Stone, which can be used to achieve immortality. Ron repeats the word "immortal" in surprise, only for Hermione to explain "It means you'll never die," just in case any of the kids in the audience don't know that word. Ron gets indignant and says "I know what it means," because there's really no reason for him not to.
There's a strange in-universe example in the first chapter of Prisoner of Azkaban; a school textbook Harry is reading feels the need to explain to its readers what "Muggle" means.
In the Daily Prophet, Muggle terms are occasionally defined to the readers: a gun is a "kind of metal wand which Muggles use to kill each other", and a policeman is "a Muggle law-keeper".
In Harry Potter and the Goblet of Fire, the text reminds the reader of the purpose of Polyjuice Potion, which becomes significant near the end of the book. This reminder is missing in the film, which would make the film harder to understand for somebody who had not seen Harry Potter and the Chamber of Secrets.
A Hole in the Fence: As telling Grisón how he was adopted, his adoptive mother Flammèche explains that Albert talked her into taking him in, before adding: "As you know, Albert is my father."
Honor Harrington: Every single book has this at least once, maybe twice. Most of these recaps appear to be at the end of a meeting that just talked about the recapped stuff. These meetings often take up a chapter, and their sole purpose is just to recap the situation and tell the reader what everyone's going to do.
CS Forester neatly justifies it in a couple of places in the Horatio Hornblower books, where a junior officer begins an explanation to a senior officer with this in order to maintain a properly deferential tone while in fact telling the senior officer something he probably didn't know, but should have known.
Orson Scott Card's manual How to Write Science Fiction & Fantasy includes an entire chapter about how to how to handle exposition in a Speculative Fiction tale without resorting to this trope. Card notes that this trope was very common in the early days of SF, and he provides a humorous example of what it often sounded like:
"As you know, Dr. Smith, the rebolitic manciplator causes the electrons of any given group of atoms to reverse their charge and become anti-electrons." "Yes, Dr. Whitley, and of course that will cause an immediate explosion unless the rebolitic manciplation is conducted inside an extremely powerful Boodley field." "And the only facility in Nova Scotia that is capable of maintaining a Boodley field of sufficient power is—" "That's right. Dr. Malifax's lab on his houseboat in the Bay of Fundy."
In Brian Herbert and Kevin J. Anderson's Hunters of Dune, the old couple Daniel and Marty do this a lot in the last chapters (when it is revealed that they are really Omnius and Erasmus.)
A top secret memo in Icons by Margaret Stohl explains "as we all know, the Lords activated the Icons and [killed one billion people]," just in case the ambassador to the aliens forgot that they conquered the planet.
The problem is routinely — and hilariously — lampshaded by narrator Bertie Wooster in the Jeeves and Wooster stories by P. G. Wodehouse, since the plot arcs often span several books.
Justified in the John Rain series by Barry Eisler by having Rain be Properly Paranoid, so he keeps explaining things to his co-workers (much to their annoyance) to ensure that they are all thinking on the same page or understand the need for his excessive security precautions.
The T'ang Chinese characters in the Judge Dee mysteries spend a surprising amount of time explaining their own culture and customs to each other for the benefit of the Western readers.
About half of Fredric Brown's short story "Keep Out" is one character giving backstory to a group of other characters, including the narrator, who then tells the reader, "Of course we had known a lot of those things already."
Knowledge of Angels: The Inquisitor reminds Severo the Inquisition's authority overreaches that of the local cardinal where heresy is concerned, something Severo retorts he already knows.
Svein: I will believe in the banner's magic power, only when you have fought three battles against your nephew King Magnus and won all three of them. Harald: (angrily) I am well aware of my kinship with Magnus without needing you to remind me of it...
Susanna Clark's Jonathan Strange & Mr. Norrell has an unending supply of footnotes stuffed with as-you-know facts about the world of British magic, as well as strange anecdotes, discussions of magical theories and other "as you might already know but may well find interesting" divergences from the main story.
In Victor Hugo's Les Misérables it is very, very common to insert a large portion of Real Life historic data that the reader is expected to already know, but Hugo still would like to remind them.note And it does help those that skipped their history class... Or are just skimming through the book...
Narrator: The arrest of the pope took place, as we know, on the night of the 5th of July.
Justified in the Lord Darcy books, where Master Sean natters on about the underlying principles of whatever spell he uses to examine crime scenes and clues, even though Darcy's surely heard all this before. Darcy actually insists that Sean do this, as it helps him overcome his own innate Muggle mental blocks about how magic operates; plus, as Master Sean is also a professor, he performs best while in classroom-lecture mode. Darcy also claims to almost always learn some new little tidbit of information each time.
The novel Mirage by James Follett is based on the real-life espionage by Israel of the blueprints of the Mirage fighter aircraft after France stopped supplying the aircraft and parts after the initial sale and Israel wanted to keep the ones they had in flying condition (and eventually built their own version, the Kfir). During the briefing given during the planning of the operation a politician asks why they can't simply reverse-engineer or copy parts from their existing stocks or by removing them from planes. While one engineer who obviously knows why has a "for god's sake" reaction a second, more people-savvy engineer cuts him off saying that from a layman's perspective it's a reasonable question and deserves an answer. He then explains about while they might be able to physically copy the shape of a particular part it's much harder to exactly duplicate the alloy used and the manufacturing processes, such as the correct hardening and tempering required to make the part able to correctly handle the stresses involved in combat flight conditions. He uses the analogy of his pocket lighter, saying that if they made their best efforts, they could eventually duplicate the lighter but its performance would be inferior to the production model and prone to malfunction and unexpected failures. Multiplying the few components of the lighter up to thousands of parts in a modern jet fighter makes the entire idea untenable. The politician then understands why detailed blueprints with all of the technical specifications of each part are required and gives the go-ahead for the espionage attempt.
Early on, Nephis Courage Story Of A Bad Mormon includes an Info Dump on Mormon theology in the form of an as-you-know debate between two characters, presumably for the benefit of non-Mormon readers.
Subverted in the Orphans of Chaos trilogy: "Headmaster Boggin" starts off on one of these at the appropriate time to provide valuable backstory to the eavesdropping protagonists, but is immediately headed off by the audience, who point out that they already know what he's talking about.
In Otherland, the first meeting between the Grail Brotherhood that the readers see is liberally peppered with As You Know, despite occurring close to the culmination of their Evil Plan. Justified by having Dedoblanco play The Watson by having failed to Read the Freaking Manual, much to the exasperation of Jongleur, the group's leader.
The Personal Librarian: Belle sometimes uses "As you surely know..." in arguments to point out a fact that the other character has neglected or refused to take into account.
Hugo Gernsback's classic SF novel Ralph 124C 41+ frequently uses this phrase to explain how the future works.
Lampshaded in a Redwall book where an important tribal custom is explained to the son of the recently deceased chieftainnote For the record, there's a sword with a wavy edge (the sea) and a straight one (the land). The chieftain throws the sword, and whichever side lands up determines the way they travel. He yells at the minion telling him this to get to the point note The minion is showing him how make the sword land the way he wants it to.
There are several scenes in Rhythm of War where Navani asks people questions that she'd already asked earlier, perhaps changing the wording slightly. When challenged on this, she explains that she's doing it to make sure that she really does know the answers, that she isn't making bad assumptions or missing important details.
[Sparhawk takes cover as a troop of soldiers marches by] Lieutenant: It's that place in Rose Street where the Pandions try to hide their ungodly subterfuge. They know we're watching, of course, but our presence restricts their movements and leaves his Grace, the primate, free from their interference. Corporal: We know the reasons, Lieutenant. We've been doing this for over a year now.
Within the first chapter of the original Shannara book a character tells "As you know, [Entire history of the world]". The narrator later tells the "real" history of the universe, adding in things that were omitted from the widely-known history.
Averted in Sheep's Clothing. While the reader probably knows a thing or two about vampires, Doc—and most frontier folks west of the Mississippi—isn't familiar with them at all.
Sort of, in Splinter of the Mind's Eye. Luke Skywalker, pretending to be a local miner, asks a real local a question about the locale. The response starts with an as you know — the real local thinks Luke knows the first part of what he's imparting, though just like the readers, he does not.
Played with in Star Carrier: Earth Strike when Rear Admiral Koenig explains to his Senate liaison John Quintanilla why the way their engines work means they can't reinforce the twelve SG-92 Starhawks they sent on a near-cAlpha Strike at the start of the book. Quintanilla's a civilian and probably doesn't understand this stuff.
In Star Darlings, one of the first things learned in the books and web series is the basics of wish-granting, which the characters know already.
Aunt Jocelyn in Strength & Justice: Side: Justice says this phrase word for word while telling Teremy the reason why anyone can possess a superpower. It's very clearly for the benefit of the reader, since Teremy obviously knows it already.
Talion: Revenant: Done many times, though it's mostly while introducing things they don't previously know (or in Nolan's case, internally reflecting) so the usage is more plausible than most.
In The Terminal Man by Michael Crichton, a forensic pathologist tells psychiatrist Janet Ross "As you know, the male pubic hair" is different from the female pubic hair. Ross replies, "No, I didn't know that." The pathologist offers a reference.
The pastor gives an overview of the history of his church because "I see some new faces in the congregation today."
Ernie does not always pay attention to what Sam tells him. For example, when Ernie asks where Sam's coworker's party is, Sam responds, "Brandenburg Township, as I said."
Timeline: This is used frequently, with the exact words, all throughout the book.
The final novel in the Tower and the Hive series by Anne McCaffrey opens with a scene in which not only do the characters recap the previous novels to each other, but in order to make it clear to the reader who he's talking about, Thian Raven-Lyon refers to his grandparents as "Jeff Raven and Angharad Gwyn, a.k.a. the Rowan".
In early 20th century dystopian sci-fi, Yevgeny Zamyatin's We averts this: the novel, written as a journal, is addressed to an alien readership; therefore, it's natural that the narrator explains some of the most basic facts of his everyday world.
Subverted by Robert Jordan: he seems to beat this trope to death with the copious amounts of exposition in his Wheel of Time series to recap events already firmly established in previous novels in the series, many of which was delivered through character dialogue; somewhat justified by the Door Stopper size of the series and difficulty in keeping track of the myriad of dangling plot threads one might think. But the reiterations most often are either new information for one or more of the people present, discussions about different opinions, or depictions of events that were influenced by the ones shown in earlier books.
The Witches: During the Grand High Witch's explanation of her plan to wipe out all the children in England, she tells her audience that "money is not a problem to us witches as you know very well" because she prints her own money for them. This is done to remind the audience that the Grand High Witch has a money-printing machine after it was initially brought up by the protagonist's Grandmama a few chapters earlier.
From the book Wonderstruck, we have this clunky bit of exposition (granted, considering that part of the story was told entirely in pictures, it was hard to do it any other way):
