1033: Formal Logic

Explain xkcd: It's 'cause you're dumb.
Revision as of 10:51, 26 July 2016 by (talk) (Transcript: spelling correction)
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Formal Logic
Note that this implies you should NOT honk solely because I stopped for a pedestrian and you're behind me.
Title text: Note that this implies you should NOT honk solely because I stopped for a pedestrian and you're behind me.


This comic is a riff on bumper stickers that say "honk if you love ____". Here, the subject is formal logic, but the word "if" is replaced with a formal logic term "iff," which means "if and only if".

"If and only if" connects two statements, saying that either both statements are true, or both are false. In this case, either someone likes formal logic and honks, or doesn't like formal logic and doesn't honk. The title text further elaborates on this, describing a practical situation (that is, stopping for pedestrians) and dissecting it with formal logic terms.

The joke is the contained self-reference. You have to love formal logic to take the sticker seriously and honk for exclusively that reason. The title text reveals the sticker is actually there to stop people from honking at him altogether, because Randall understandably hates it when he yields for pedestrians only to get honked at by some impatient driver behind him; the ONLY reason you're allowed to honk is to declare your love for formal logic.


[The rear end of a car (with an unreadable license plate), with a bumper sticker over the tailpipe to the right:]
Honk iff you love
formal logic

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- What can we learn from this? - I've learned that everyone who drives a car loves Formal Logic that if they press a horn actuator while driving, a horn will sound (Thank you Mr. XKCD). Now can I comment if I love your undeniable genius and your unexpected life's lessons? - E-inspired (talk) 14:36, 28 February 2013 (UTC)

"So, there is nothing you can do except starting to love formal logic" That isn't what this comic means. It means "I am a fan of formal logic, and if you are too, you may honk to indicate this. If you honk for any other reason at all, don't be surprised if I jam a pitchfork up your ass." Re-write, please. 08:37, 10 February 2014 (UTC)

Why would you even think that is correct? -Pennpenn 03:19, 29 January 2015 (UTC)
Elementary, my dear! 19:50, 8 February 2015 (UTC)
It does not say "honk when you ..." 16:54, 19 May 2015 (UTC)

So, what do you do if you hate formal logic? Honk twice? (talk) (please sign your comments with ~~~~)