In linguistics, a presupposition is something that a particular utterance implies or takes for granted as true. For example, the classic “When did you stop beating your wife” presupposes that you have beaten your wife at some point. “Would you like more tea?” presupposes that you have had some tea already. The word more is a presupposition trigger, and that quality of the word is played with by Lewis Carrol in Alice’s Adventures in Wonderland.
“Take some more tea,” the March Hare said to Alice, very earnestly.
“I’ve had nothing yet,” Alice replied in an offended tone, “so I can’t take more.”
“You mean you can’t take less,” said the Hatter: “It’s very easy to take more than nothing.”
Another category of presupposition triggers is factives, which presuppose the truth of the phrase they apply to. Examples include regret and realize. It doesn’t matter whether “I regret going to the party” or “I don’t regret going to the party,” regret triggers the presupposition that I did, in fact, go to the party.
The party, by the way, is a definite, which is its own presupposition trigger, because it assumes the truth that there was, in fact, a party for me to have gone to. Another example of a definite is when I say that “My brother is coming to visit,” which presupposes that I have a brother.
Implicative verbs presuppose a necessary precondition for the phrase they apply to. Some examples are verbs of success or failure, such as, “I have never yet managed to juggle four balls at once.” Manage presupposes that I have, in fact, tried to juggle four balls at once. Change-of-state verbs are similar in presupposing that an earlier state existed before it changed. That’s the famous “When did you stop beating your wife” or “Pandora opened the box,” which triggers the presupposition that the box was closed before her curiosity got the better of her.
Okay, so this is kind of interesting, but so what? The strange thing is that people accept the presuppositions they hear, but rarely remember where the knowledge came from. Some time later you will have it in your head that I have a brother, but you are much less likely to remember how you know it. Did I tell you? Did someone else tell you? Have you actually met him once, perhaps? The vast majority of the time this works well for communication; it helps us impart information efficiently and interpret speech without excess confusion. When people converse they follow the rules in good faith, happily triggering and accepting presuppositions that are, in fact, true. But presuppositions can also be manipulated. Carroll manipulated our presuppositions for humor, while shady lawyers can manipulate the jury’s presuppositions for dishonest purposes, and politicians and push-pollsters routinely manipulate presuppositions in order to spread lies while claiming that they never actually lied. This is distressingly effective because of our brains’ oh-so-efficient presupposition shortcuts in absorbing information.
There is one more place this mental characteristic can be manipulated, but for less nefarious purposes. This is how writers of mysteries can lead us subtly astray without breaking the rules of Whodunnit Fair Play, thus setting us up to be surprised and delighted by the eventual denouement. If false information is slipped to us in the form of characters’ presuppositions, we are extremely likely to accept it as true, but then also willing, when the real solution is eventually explained, to accept that we were tricked fair and square. As a writer I’ve used these techniques all along, but it’s interesting to see it dissected and understand why it works.
[Pictures: A Mad Tea Party, illustration by John Tenniel, wood engraving by Thomas Dalziel from Alice’s Adventures in Wonderland by Lewis Carroll, 1865;
Nothing Could Be Better, illustration by Sidney Paget from The Adventure of the Stockbroker’s Clerk by Arthur Conan Doyle, 1893.]