# 982: Set Theory

## [edit] Explanation

This comic is a pun on the phrase "Proof by Intimidation" which normally is a jocular term used mainly in mathematics. It refers to a style of presenting a purported mathematical proof by giving an argument loaded with jargon and appeals to obscure results, so that the audience is simply obliged to accept it, lest they have to admit their ignorance and lack of understanding.

However, in this comic, "Proof by Intimidation" is taken to mean that by intimidating the elements within a set, they will conform to the proof (or, as the title text says, they will become "well-ordered"). This is accomplished by believing that the elements can be anthropomorphized such that they feel fear. The idea of executing as an example was exemplified by Sun Tzu in the ancient book The Art Of War.

The axiom of choice (which has been referenced in previous xkcds) says that given any collection of bins, each containing at least one object, it is possible to make a selection of exactly one object from each bin.

In the title text, the well-ordering theorem states that every set can be well-ordered. A set X is well-ordered by a strict total order if every non-empty subset of X has a least element under the ordering. This is also known as Zermelo's theorem and is equivalent to the Axiom of Choice. The woodchipper is a reference to the 1996 film Fargo (film), where a character uses one to dispose of a body.

There is another layer to the joke. If you can feed the set to the wood-chipper, that defines an ordering on the set (the order in which the elements are fed to the wood chipper) which would be well-ordered. Hey, look, the set really is well-ordered! If there were no way of defining a well-ordering on the set, you wouldn't be able to feed it to the wood-chipper.

## [edit] Transcript

- [Ponytail stands at a blackboard, facing away from it. She has a pointer in her hand, and written on the blackboard is some set theory math, although one of the set elements is being pointed into a guillotine.]
- Ponytail: The axiom of choice allows you to select one element from each set in a collection
- Ponytail: and have it
*executed*as an example to the others. - My math teacher was a big believer in Proof by Intimidation.

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# Discussion

If your math paper isn't working out, rip it up to show it who's boss! __Davidy__^{22}`[talk]` 06:57, 2 February 2013 (UTC)

Actually the "making an example by execution" is indeed in the Art of War, but AFAIK was not performed by Sun Tzu, it was done by one of his predecessors, who was challenged to make an army of the Emperor's concubines.--141.101.89.203 14:48, 7 April 2014 (UTC)

:My math teacher was a big believer in Proof by Intimidation.

Sums up the English Educational system and popular western culture until the Hippy era broke that particular example of sharia law. (Lest we forget!) I used Google News BEFORE it was clickbait (talk) 08:34, 22 January 2015 (UTC)