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    • CommentRowNumber1.
    • CommentAuthorDmitri Pavlov
    • CommentTimeAug 19th 2020

    Corrected a hyperlink. Removed the publication year from the page title.

    diff, v2, current

    • CommentRowNumber2.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 16th 2025

    Added colloquial name and link to Elephant

    diff, v6, current

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeMay 16th 2025

    If you ask me, I find it (a) silly, (b) not even clever (as the “Elephant” is not the book but the theory), (c) dubious (asking a common AI to tell me who says “Baby Elephant” for Johnstone’s book and the only pointers it finds are to the nLab) and (d) distracting and pointless. I vote for reverting this edit.

    • CommentRowNumber4.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 16th 2025

    I did search (not using AI, but a search engine, and read the text using the phrase, in context) before making the edit, and there are people on MathOverflow using the phrase, at least (well, I used it, but the person I was talking to knew what I meant, and used it themselves) at least Todd used it at the n-café in 2011 and here in the forum in 2012), and it found I used it at least twice on the categories mailing list) over the years, presumably without people misunderstanding me. I find it a cute appellation that it is useful to record in case people come across the phrase. I personally find “Cats and Alligators” less than moving, the joke being made at a different time in history, but it’s also a matter of it being a (rare, arguably) recorded nickname for the book Categories, Allegories, which is why I added that to its page. Perhaps the fact I seem to have used the phrase on the internet may make my case weaker, but it didn’t originate with me, and is certainly not just in the nLab proper.

    The fact topos theory was a baby small enough to fit into that relatively slim volume in 1977, compared to the two thick volumes a quarter-century later makes the metaphor stronger, in my mind.

    • CommentRowNumber5.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 16th 2025

    One could ask Todd where he got the name from :-)

    • CommentRowNumber6.
    • CommentAuthorJonasFrey
    • CommentTimeMay 16th 2025
    • (edited May 16th 2025)

    I can confirm that a lot of people call the two-volume book the “Elephant” (not the theory).

    Regarding the first book, I heard at least one person call it the “mouse” :-)

    I’ve also heard people call locale theory “baby topos theory”, so maybe the baby elephant should be a book about locales?

    But seriously, if anybody mentioned “baby elephant” to me, I’d assume they’re talking about Johnstone’s first book.

    • CommentRowNumber7.
    • CommentAuthorUrs
    • CommentTimeMay 17th 2025

    I think it’s just noise made by swallowing low-hanging red herrings, not conducive to the purpose of the nLab. Not everything that people say when they feel like making a joke needs to be forcefully elevated to canon. In the past these kinds of lame jokes have already caused us a good deal of work to get rid of them (like the notorious “evil”, “walking” and, yes, the habit of one contributor to reference Elephants). Think of newcomers, outsiders, maybe sceptical of category/topos theory — one day they finally go to look up what the nLab has and the first thing highlighted to them are uninspired jokes, not even witty, not even common, about titles of the main textbooks.

    I still vote for reverting the edit.

    • CommentRowNumber8.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 17th 2025

    If it’s worrying about newcomers getting a certain first impression, one can move it down the page. The nLab page principle of equivalence still mentions the joking term “evil”, where that was a lighthearted joke that carried too much moral overtones and so outlived it’s welcome. But documenting this term is useful, given its presence in a range of places, and I don’t think it should be deleted there. Something like a fond nickname of a book that helps disambiguate between Johnstone’s two influential topos theory books, and with no value judgment aspects, feels much less questionable.

    • CommentRowNumber9.
    • CommentAuthorDmitri Pavlov
    • CommentTimeMay 18th 2025

    We can apply the same criterion as in étale space (formerly étalé space): if there is an officially published source that uses “baby Elephant”, then it should probably be mentioned in the article. For étalé space, eventually an obscure book using it was found.

  1. Removed the “baby Elephant” from the article since there are no citations for this term. See the note on the nLab’s HomePage.

    Stanley Baldwin

    diff, v8, current

    • CommentRowNumber11.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 19th 2025
    • (edited May 19th 2025)

    I disagree in the strongest terms with removing non-crank items that don’t have a citation to justify them. We would be deleting large chunks of the nLab if so. And the nLab would cease to be a place where folklore can be written down for the first time.

    The nlab can take a descriptive approach here. Todd says the term didn’t originate with him, fwiw, but can’t recall where he got it from.

  2. Jonas Frey on the category theory Zulip pointed out that the issue here (and with “evil”, “walking”, etc) isn’t about folklore (i.e. theorems).

    It’s about what terminology to use and include in the nLab, which is a separate issue from folklore.

    • CommentRowNumber13.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 19th 2025

    But writing down a folklore lemma without a source seems to me to much more against the spirit, such as it is, of the requirement to have citations for content. If this is intended to protect the nLab against spurious content, then a terminology used largely (or wholly) outside formal publications is much less harmful than someone claiming an actual piece of mathematics is true. Does this mean folklore needs to be somehow peer-reviewed to appear on the nLab, if it isn’t written down anywhere? And what’s the threshold for needing a citation?

    • CommentRowNumber14.
    • CommentAuthorMadeleine Birchfield
    • CommentTimeMay 19th 2025
    • (edited May 19th 2025)

    From the changes Urs Schreiber has made to the HomePage, I think we can safely assume at this point that the citations are needed for terminology (the issue here), and that folklore theorems don’t need a citation and can be justified by a written proof on the page itself.

    The issue we were having on the nLab in the past was that anonymous editors were mass creating pages of original research like skeletal type that didn’t appear anywhere in the existing literature, so we needed something to prevent that from happening. And requiring citations only for the terminology would work just as well and wouldn’t infringe on folklore theorems on the nLab.

    • CommentRowNumber15.
    • CommentAuthorUrs
    • CommentTimeMay 19th 2025

    I have adjusted the wording of that clause on the Home page, annouced here:

    Edits should be substantiated according to common academic practice. That may be a literature citation, may be a proof spelled out, or other sanity checks.

    The objections I made to your edit above was not that a citation was lacking (though citations would trump such objections, as just happened here in the other thread on “walking structure”) but that it makes no good sense and is not beneficial. So the only justification you gave for the edit was that you heard a couple of people make or repeat a thoughtless joke, which I don’t doubt, but which is not good reason (or common academic practice) to include it.

    • CommentRowNumber16.
    • CommentAuthorUrs
    • CommentTimeMay 19th 2025

    Compare to the usage “The Orange Book” and the “The Green Book” to refer to writings by Doug Ravenel. These are active usages within the respective community and it is actually useful information to say what is meant by these coinages. (And, ironically, the nLab doesn’t, somebody should add that here – myself, I have to run now),

    • CommentRowNumber17.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 19th 2025
    • (edited May 19th 2025)

    So the only justification you gave for the edit was that you heard a couple of people make or repeat a thoughtless joke,

    I do not think that people were making a thoughtless joke at all. Rather, I think the term is a rather well-considered back-formation that succinctly captures several difference aspect of the relation between the two books, the temporal gap, the maturation of the field of topos theory, as well as being more unambiguous than a phrase like “Johnstone’s topos theory book”. When I used the term it was intentional and when I did, the person I spoke with (who I have never met or spoke with before, to my recollection) knew what I meant without any explanation. Not to get all Wittgenstein, but this to me shows it’s not a term from a private language.

    I say the above as someone who doesn’t always appreciate cute in-jokes by category theorists of a certain age (“klttygories”? really? “Cats and Alligators” is not really a good nickname imo, despite it being amusing for my young daughter, but it’s on record as being used by one of the authors of his own book)

    • CommentRowNumber18.
    • CommentAuthorvarkor
    • CommentTimeMay 19th 2025

    “klttygories”? really?

    Perhaps off-topic, but what does this term mean?

    • CommentRowNumber19.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 19th 2025
    • (edited May 19th 2025)

    A kittygory is a small category.

    • CommentRowNumber20.
    • CommentAuthorDavidRoberts
    • CommentTimeMay 19th 2025

    My standards for names for mathematical objects are much higher than nicknames for books, I should add. And I say this having tried to invent a bilingual literary pun for the name of a class of objects as a PhD student, a fact I now cringe at.

    • CommentRowNumber21.
    • CommentAuthorTodd_Trimble
    • CommentTimeJun 4th 2025

    Is “kittygory” due to Freyd?

    • CommentRowNumber22.
    • CommentAuthorDavidRoberts
    • CommentTimeJun 4th 2025

    I think so.

    • CommentRowNumber23.
    • CommentAuthorMike Shulman
    • CommentTimeJun 4th 2025

    I think mentioning “baby Elephant” on this page is fine. I don’t want the nLab to become all wikipedia and require citations for everything. We need a certain amount of filtering to block cranks, but I think it’s good that the nLab can be a place to record folklore and in-group names like this.