# 1033: Formal Logic

 Formal Logic Title text: Note that this implies you should NOT honk solely because I stopped for a pedestrian and you're behind me.

## Explanation

The key part of this comic is "IFF", which in formal logic means "if and only if". "If and only if" represents a formal logic connector that the result is that the truth of either one of the connected statements requires the truth of the other, i.e., either both statements are true, or both are false. In the comic, if someone honks at this car, it means they like formal logic, there is not any other possible reason per this bumper sticker. (As we see in the image text.)

The joke is the contained self-reference. You have to love formal logic to take the sticker serious and honk for exclusively that reason.

But if you don’t love formal logic you would dislike the sticker at all and try to do something contradictory. And now the problem begins: If you don’t honk to contradict the sticker completely you automatically follow its instruction. So, there is nothing you can do except starting to love formal logic.

## Transcript

[Vehicle with a bumper sticker:"Honk iff you love formal logic"]

# Discussion

- 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. 108.162.219.58 08:37, 10 February 2014 (UTC)

Why would you even think that is correct? -Pennpenn 108.162.249.205 03:19, 29 January 2015 (UTC)
Elementary, my dear 108.162.219.58! 108.162.254.148 19:50, 8 February 2015 (UTC)
It does not say "honk when you ..." 141.101.104.55 16:54, 19 May 2015 (UTC)