Explain xkcd: It's 'cause you're dumb.
Cueball explains the principle of explosion, a classical law of logic, that says that if you start out with premises (axioms) that are contradictory, it is possible to derive (prove) any statement in the language you are working in, true or false. (In math for example, if you assume that √2 is a rational number, you can prove things that are obviously false. Consequently you draw the conclusion that √2 is an irrational number. This is how proof by contradiction works.)
His friend misinterprets this to mean that you can derive any fact about the physical world. He starts with a formula of propositional logic that says "P and not-P", where P is a proposition. To say that P is both true and false is a contradiction, it's false regardless of whether P is true or false. To Cueball's bewilderment he then successfully derives his mom's phone number. His mom turns out to be Miss Lenhart (now a Mrs?), and to his vexation she asks his friend out.
- [Cueball is talking to his friend.]
- Cueball: If you assume contradictory axioms, you can derive anything. It's called the principle of explosion.
- Friend: Anything? Lemme try.
- [Cueball's friend is writing on a piece of paper on a desk.]
- [Cueball's friend is holding up a piece of paper to Cueball, while holding a phone.]
- Friend: Hey, you're right! I started with P∧¬P and derived your mom's phone number!
- Cueball: That's not how that works.
- [Cueball is looking at the piece of paper, while his friend is talking to someone on a phone.]
- Friend: Mrs. Lenhart?
- Cueball: Wait, this is her number! How—
- Friend: Hi, I'm a friend of— Why, yes, I am free tonight!
- Cueball: Mom!
- Friend: No, box wine sounds lovely!
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Could Mrs Lenhart be Miss Lenhart's mother, perhaps? This makes Cueball-1 Miss Lenhart's brother (and thus possibly "Cueball Lenhart", unless he's a half-brother or step-brother or the like). Of course with provably two Cueballs in this situation (and assuming they aren't twins, unless #2... no, we won't go there) we can't therefore assume that any particular lone Cueball is related. However, if "Cueball is a Lenhart AND Cueball is not a Lenhart" then.... well, lock up your mothers... <smirk> 22.214.171.124 22:01, 7 May 2013 (UTC)
^ genealogy makes my head durt. 126.96.36.199 20:22, 19 October 2013 (UTC)
Hey, what do waffle cones and box wine have to do with each other? Wouldn't the cones just get soggy? Just wondering. Anonymous 18:30, 9 December 2014 (UTC)
- This is what I came here to figure out. "Oh, right, for the wine" makes it sound like it's supposed to be obvious. 188.8.131.52 00:51, 28 March 2015 (UTC)
- Logically the waffle cones are unrelated to the wine, it's a separate item. -Pennpenn 184.108.40.206 00:55, 18 May 2015 (UTC)
- I thought the joke was that Cueball's mother was cheap and tasteless because she enjoys drinking boxed wine out of waffle cones. 220.127.116.11 17:24, 28 September 2015 (UTC)
- Using the principle of explosion, boxed wine and waffle cones are very much related, and are essentially the same thing. 18.104.22.168 01:29, 7 August 2015 (UTC)
Gah, unpaired parentheses... 22.214.171.124 05:48, 17 August 2015 (UTC)
- I added the end parenthesis, just for you. Although, now I'm wondering if double parentheses are really the best alternative... --Hammy2211 (talk) 17:09, 8 October 2015 (UTC)
There was a community portal discussion of what to call Cueball and what to do in case with more than one Cueball. I have added this comic to the Category:Multiple Cueballs. Since here it is clearly the Cueball that calls the mom who is the protagonist and do the important "talking" of this comic he should be listed as Cueball (if any of them). So have rephrased the explanation to take this into account and also noted that the "friend" also looks like Cueball... --Kynde (talk) 15:44, 24 November 2015 (UTC)