704: Principle of Explosion

Explain xkcd: It's 'cause you're dumb.
(Redirected from 704)
Jump to: navigation, search
Principle of Explosion
You want me to pick up waffle cones? Oh, right, for the wine. One sec, let me just derive your son's credit card number and I'll be on my way.
Title text: You want me to pick up waffle cones? Oh, right, for the wine. One sec, let me just derive your son's credit card number and I'll be on my way.

[edit] Explanation

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.

Waffle cones are a variety of ice cream cone. The rest of the title text is just more of the main comic's derivation joke, since Cueball's "friend" is apparently a cheap bastard who can't spare five bucks to buy his own ice cream cones.(Unless he is smart enough to exploit the system of universe)

[edit] Transcript

[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!
comment.png add a comment!

Discussion

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> 31.111.50.225 22:01, 7 May 2013 (UTC)

^ genealogy makes my head durt. 103.9.42.158 20:22, 19 October 2013 (UTC)
Personal tools
Namespaces

Variants
Actions
Navigation
Tools

It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal or Bitcoin?