--- title: One counterexample is enough — a lesson of Mova's school · trees and pragmatics description: «One counterexample is enough», a lesson of the world course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Big words like "all", "every", "never" and "nobody" make big claims, and big claims are fragile: one clear example the other way, a counterexam --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [World](https://md.mova.elamur.ai/free/en/corpora/school/world/) / One counterexample is enough # One counterexample is enough Lesson 187 of the world course of Mova's primary school: 21 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/world/187-one-counterexample-is-enough/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/0/) — Big words like "all", "every", "never" and "nobody" make big claims, and big claims are fragile: one clear example the other way, a counterexample, knocks them down. - [1](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/1/) — Freddie says, "All swans are white." His friend shows a photo of a black swan from Australia. - [2](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/2/) — One black swan, and "all" is gone: "It's a swan, bro, and it's black. 'All' just died." - [3](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/3/) — The trick to watch for is the excuse: "That one doesn't count", "Well, that dog's weird." Calling the counterexample names doesn't make it go away. - [4](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/4/) — It's lopsided in a funny way: ONE example breaks "nobody can", but to PROVE "nobody can" you would have to check everybody. - [5](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/5/) — The fix is easy and honest: swap "all" for "most". - [6](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/6/) — "Most dogs can't climb trees" is true; "dogs can't climb trees" is not. - [7](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/7/) — One clear example that breaks an "all", "never" or "nobody" claim shows the claim is false. - [8](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/8/) — Black swans live in Australia, so "all swans are white" is false. - [9](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/9/) — Saying a counterexample "doesn't count" or is "weird" doesn't make it go away; grown-ups call this the "no true Scotsman" move. - [10](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/10/) — England's women's football team, the Lionesses, won the European Championship in 2022 and again in 2025; Sam Kerr and Alexia Putellas are among the world's best players. - [11](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/11/) — Mudskippers are fish that spend lots of time out of the water, on mud. - [12](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/12/) — One person doing a backflip breaks "nobody can"; to prove "nobody can" you would have to check everyone. - [13](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/13/) — The platypus and the echidnas (spiny anteaters of Australia and New Guinea) are mammals that lay eggs; most mammals give birth to live young. - [14](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/14/) — Lots of older people use technology well; a rule about everyone of one age is a stereotype. - [15](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/15/) — Most dogs can't climb trees well, but some can scramble up. - [16](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/16/) — Spiders are arachnids, not insects: spiders have 8 legs and 2 body parts, insects have 6 legs and 3 body parts. - [17](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/17/) — People can learn and enjoy sports at any age. - [18](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/18/) — In Britain it rains in every month of the year, summer included. - [19](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/19/) — Mercury is a metal that is liquid at room temperature, and sodium is a metal soft enough to cut with a knife. - [20](https://md.mova.elamur.ai/free/en/corpora/school/world/187-one-counterexample-is-enough/20/) — Words people use: "W" means a win; "cheat code" means a secret way round a game's rules; "that's a vibe" means "that's cool"; "dinnae" (Scotland) means don't; "hen" (Glasgow) means dear; "chuckin' it doon" (Scotland) means pouring with rain. - ← previous: ["How do you know?"](https://md.mova.elamur.ai/free/en/corpora/school/world/186-how-do-you-know/) - next →: [Check the claim, not the person](https://md.mova.elamur.ai/free/en/corpora/school/world/188-check-the-claim-not-the-person/) - ↑ back to [World](https://md.mova.elamur.ai/free/en/corpora/school/world/)