explain xkcd - User contributions [en]

Talk:3201: Proof Without Content

2026-01-31T09:13:08Z

Hcs:

First. Would be funny to have an explanation along the lines of "It is possible to give an explanation with no content. Here's how:" [[User:R128|R128]] ([[User talk:R128|talk]]) 17:44, 30 January 2026 (UTC)

Proof without Content seems to be a play of words for [https://en.wikipedia.org/wiki/Proof_without_words]Proof without Words

The comic pokes fun at a common situation found in mathematics books. The students sees a statement with a very short proof that doesn't make sense since it's been summarized in a way that is helpful for people already familiar with the theorem. For instance: "prime numbers larger than 2 are odd". Proof: "even numbers are divisible by 2". The student is expected to know that a number divisible by 2 is not prime, but that's most likely something that comes up later in the same book, or sometimes not explained at all.
In the comic the "short" proof is taken to the absurd level of being completely empty. What mathematical statement can be proven with a completely empty proof? The fact that there exists comics which have statements with empty proofs. It is both a joke about difficult to understand proof in math books and also a meta-mathematics joke as the proof is talking about itself.
The title text pokes even more fun at maths books where many important theorems are stated and are given to the students as useful facts but with no proof, stating that demonstrating the truth of the statement is so easy it is "left as an exercise for the reader". This common scenario frustrates students because in some cases the "exercise" is extremely difficult to do.
The only "proof without content of a conjecture without content" is a blank page altogether, which clearly exists, so the statement is true, even if meaningless.
:I don't recall that problem with such a proof. Usually the statement about primes being odd comes after giving the definition of prime and composite numbers. From that, being divisible by 2 clearly makes a number composite. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:31, 30 January 2026 (UTC)
::You must be very smart. [[Special:Contributions/2600:1700:2120:5880:C885:5DAF:EFD8:EADF|2600:1700:2120:5880:C885:5DAF:EFD8:EADF]] 22:12, 30 January 2026 (UTC)

I really do not get that title text. I put an attempt at understanding it down but it may have gone over my head [[User:R128|R128]] ([[User talk:R128|talk]]) 17:58, 30 January 2026 (UTC)

The comic demonstrates a proof without content, but is it a <i>convincing</i> proof? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:33, 30 January 2026 (UTC)
:If it is, then yes. QED. ;) [[Special:Contributions/81.179.199.253|81.179.199.253]] 21:14, 30 January 2026 (UTC)

I think the tautological nature of the proof could be better explained. If the blank image is interpreted as a correct proof, it proves the notion that a blank image can prove a conjecture. [[Special:Contributions/2600:4041:2E5:B900:6C41:5AFB:89D1:F216|2600:4041:2E5:B900:6C41:5AFB:89D1:F216]] 22:11, 30 January 2026 (UTC)

Isn't this proof using circular reasoning? The proof is only convincing if the conjecture that an empty proof can be convincing is correct. [[Special:Contributions/73.222.207.213|73.222.207.213]] 23:26, 30 January 2026 (UTC)
:Yeah, it is a circular argument. Maybe that’s part of the joke? [[User:Logalex8369|Logalex8369]] ([[User talk:Logalex8369|talk]]) 01:39, 31 January 2026 (UTC)
::I say it's only circular reasoning if it's circular reasoning. [[Special:Contributions/81.179.199.253|81.179.199.253]] 02:01, 31 January 2026 (UTC)
:Yes, it really begs the question... [[Special:Contributions/136.47.216.1|136.47.216.1]] 03:42, 31 January 2026 (UTC)

This space provably left blank [[User:Hcs|Hcs]] ([[User talk:Hcs|talk]]) 09:13, 31 January 2026 (UTC)

Talk:3131: Cesium

2025-08-20T14:45:34Z

Hcs:

I think that's called a recipe for disaster. [[Special:Contributions/138.43.101.123|138.43.101.123]] 14:36, 20 August 2025 (UTC)
My best recipe comes with a Notice to Mariners [[User:Hcs|Hcs]] ([[User talk:Hcs|talk]]) 14:45, 20 August 2025 (UTC)

Talk:3062: Off By One

2025-03-12T21:19:34Z

Hcs:

But what about floats? [[User:GreyFox|GreyFox]] ([[User talk:GreyFox|talk]]) 20:01, 12 March 2025 (UTC)

Is this dithering? [[User:Hcs|Hcs]] ([[User talk:Hcs|talk]]) 21:19, 12 March 2025 (UTC)

Talk:3003: Sandwich Helix

2024-10-26T10:21:02Z

Hcs: moved my comment to the bottom, oops

Sandwich presumably refers to {{w|compliment sandwich}}, but I don’t know what the helix is. --[[User:Galaktos|Galaktos]] ([[User talk:Galaktos|talk]]) 14:03, 25 October 2024 (UTC)

: Maybe {{w|Models of communication#Dance}}? --[[User:Galaktos|Galaktos]] ([[User talk:Galaktos|talk]]) 14:12, 25 October 2024 (UTC)

:The word "Helix" may be a reference to the previous comic. [[User:CategoryGeneral|CategoryGeneral]] ([[User talk:CategoryGeneral|talk]]) 14:36, 25 October 2024 (UTC)

That title text makes me reasonably upset. What nitwit decided "smart quotes" AND incompatible default encodings was a good idea? [[Special:Contributions/172.70.174.203|172.70.174.203]] 16:45, 25 October 2024 (UTC)

It seems that something like this could happen over time naturally if it's a saying that "everyone knows" so that real meaning stops being said, and then eventually that bit of information disappears. For instance KISS "Keep it simple, stupid" has a negative connotation, but the idea is very sound. So people keep saying the abbreviation but stop saying the full version, and new people hearing it the first time might get the basic idea without knowing why. Eventually even the meaning could be lost, and it could just become something that people say without knowing why. Maybe the assume the ancient designers and engineers liked to make out when they saw complex things. [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 17:58, 25 October 2024 (UTC)

Frums - Options [[Special:Contributions/162.158.91.14|162.158.91.14]] 04:18, 26 October 2024 (UTC)

''KISS Keep it simple, stupid'' was originally ''keep it stupid simple''. An emphasis, not an insult. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 05:12, 26 October 2024 (UTC)

==Grammar==
Minor grammatical point; please feel free to skip this. I just tweaked "a communication technique [...] which meaning has not been lost." to "a communication technique [...] whose meaning has not been lost.". "''Of'' which ''the'' meaning" or "whose meaning" both work, but the latter is less contrived. People keep forgetting that "whose" can refer to objects, as well as to people. <https://en.wiktionary.org/wiki/whose#Determiner>

The first rule of communication is "Always talk about communication." [[User:RegularSizedGuy|RegularSizedGuy]] ([[User talk:RegularSizedGuy|talk]]) 15:36, 25 October 2024 (UTC)

==Helix==

I don't think the "helix" refers to software development. It could be about the helical model of communication, which conveys communication as a non-linear process.

This is perhaps a joke with these simplistic "rules" of communication (like the compliment sandwich), which portray communication as something much simpler.

If we assume that communication is complex and non-linear (as the helical model of communication portrays), we might conclude that there is no such thing as "#1 rule of communication"; something that could be observed by the misuse of the "compliment sandwich". {{unsigned ip|172.70.47.87|15:38+, 25 October 2024}} (Assuming all the above is the same IP editor, tweaking their comment.)

:Ah, thank you. I added the Spiral (for development) because I couldn't find the Helix one (for communication), and I thought this was the best linkable item out there. Now I know it's ''Helical'', I've found it and I can put a link on your addendum and perhaps remove my original 'placeholder'. That's collaborative communication! ;) [[Special:Contributions/172.70.91.77|172.70.91.77]] 15:56, 25 October 2024 (UTC) (PS, please sign Talk contributions, and wikilinks are a good idea if you can add them. ;p )

I took the opposite point from that in the explanation so far, especially with the title text: Even if the encoding is wrongly specified, it's possible to figure out what was meant by some sequence of bytes. I imagine the teacher using a different nonce every time to make the point about the #1 rule of communication: Words don't have inherent meaning, it is acquired through use. (Though if I'm the only one with this interpretation it kind of sinks my idea I guess). [[User:Hcs|Hcs]] ([[User talk:Hcs|talk]]) 10:18, 26 October 2024 (UTC)

Talk:3003: Sandwich Helix

2024-10-26T10:18:51Z

Hcs:

Sandwich presumably refers to {{w|compliment sandwich}}, but I don’t know what the helix is. --[[User:Galaktos|Galaktos]] ([[User talk:Galaktos|talk]]) 14:03, 25 October 2024 (UTC)

: Maybe {{w|Models of communication#Dance}}? --[[User:Galaktos|Galaktos]] ([[User talk:Galaktos|talk]]) 14:12, 25 October 2024 (UTC)

:The word "Helix" may be a reference to the previous comic. [[User:CategoryGeneral|CategoryGeneral]] ([[User talk:CategoryGeneral|talk]]) 14:36, 25 October 2024 (UTC)

That title text makes me reasonably upset. What nitwit decided "smart quotes" AND incompatible default encodings was a good idea? [[Special:Contributions/172.70.174.203|172.70.174.203]] 16:45, 25 October 2024 (UTC)

It seems that something like this could happen over time naturally if it's a saying that "everyone knows" so that real meaning stops being said, and then eventually that bit of information disappears. For instance KISS "Keep it simple, stupid" has a negative connotation, but the idea is very sound. So people keep saying the abbreviation but stop saying the full version, and new people hearing it the first time might get the basic idea without knowing why. Eventually even the meaning could be lost, and it could just become something that people say without knowing why. Maybe the assume the ancient designers and engineers liked to make out when they saw complex things. [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 17:58, 25 October 2024 (UTC)

I took the opposite point from that in the explanation so far, especially with the title text: Even if the encoding is wrongly specified, it's possible to figure out what was meant by some sequence of bytes. I imagine the teacher using a different nonce every time to make the point about the #1 rule of communication: Words don't have inherent meaning, it is acquired through use. (Though if I'm the only one with this interpretation it kind of sinks my idea I guess). [[User:Hcs|Hcs]] ([[User talk:Hcs|talk]]) 10:18, 26 October 2024 (UTC)
Frums - Options [[Special:Contributions/162.158.91.14|162.158.91.14]] 04:18, 26 October 2024 (UTC)

''KISS Keep it simple, stupid'' was originally ''keep it stupid simple''. An emphasis, not an insult. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 05:12, 26 October 2024 (UTC)

==Grammar==
Minor grammatical point; please feel free to skip this. I just tweaked "a communication technique [...] which meaning has not been lost." to "a communication technique [...] whose meaning has not been lost.". "''Of'' which ''the'' meaning" or "whose meaning" both work, but the latter is less contrived. People keep forgetting that "whose" can refer to objects, as well as to people. <https://en.wiktionary.org/wiki/whose#Determiner>

The first rule of communication is "Always talk about communication." [[User:RegularSizedGuy|RegularSizedGuy]] ([[User talk:RegularSizedGuy|talk]]) 15:36, 25 October 2024 (UTC)

==Helix==

I don't think the "helix" refers to software development. It could be about the helical model of communication, which conveys communication as a non-linear process.

This is perhaps a joke with these simplistic "rules" of communication (like the compliment sandwich), which portray communication as something much simpler.

If we assume that communication is complex and non-linear (as the helical model of communication portrays), we might conclude that there is no such thing as "#1 rule of communication"; something that could be observed by the misuse of the "compliment sandwich". {{unsigned ip|172.70.47.87|15:38+, 25 October 2024}} (Assuming all the above is the same IP editor, tweaking their comment.)

:Ah, thank you. I added the Spiral (for development) because I couldn't find the Helix one (for communication), and I thought this was the best linkable item out there. Now I know it's ''Helical'', I've found it and I can put a link on your addendum and perhaps remove my original 'placeholder'. That's collaborative communication! ;) [[Special:Contributions/172.70.91.77|172.70.91.77]] 15:56, 25 October 2024 (UTC) (PS, please sign Talk contributions, and wikilinks are a good idea if you can add them. ;p )