# Talk:Naive set theory

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Field: Foundations, logic, and set theory

## Untitled

Older discussion (2002–) is at Talk:Naive set theory/Archive 1

## Please Verify: (08/06/08)

"In symbols, A ⊆ B means that A is a subset of B, and B ⊇ A means that B is a superset of A."

This seems wrong to me, since the direction of the symbol and the elements are transposed in the second phrase. A⊆B is probably the same as B⊇A, but not the same as B⊆A or A⊇B.

Please Check!!! Thanks ~~user:lenehey

I think it is right now, but I think it is very confusing. Could we change to something like: "In symbols A ⊆ B means that A is a subset of B and B is a superset of A, whereas A ⊇ B means that A is a superset of B and B is a subset of A." (Still me.) Lenehey (talk) 19:01, 6 August 2008 (UTC)

Another Mistake?

In the 2nd paragraph of the section entitled 'Subsets' is the sentence:

Some authors use the symbols "⊂" and "⊃" for subsets, ...

The symbols "⊂" and "⊃" appear identical to me. Is this a mistake? —Preceding unsigned comment added by 115.166.28.14 (talk) 07:07, 19 April 2009 (UTC)

If those symbols appear identical to you, there's a mistake in your browser or your fontset. How *do* they appear? If they both look like a little box, or a question mark, or some nonspecific thing like that, it probably means you just don't have a font that can render them. --Trovatore (talk) 08:17, 19 April 2009 (UTC)

Yes, they looked like boxes. I was using Internet Explorer. I have viewed the page subsequently in Firefox and can see that they render differently (like different facing sideways letter 'U'). Sorry for the distraction! —Preceding unsigned comment added by 115.166.28.14 (talk) 05:53, 23 April 2009 (UTC)

## Two meanings

It's rather worse than that, and frankly I don't like the way content is assigned to article names at all. See the "Formalist POV" section in the stuff you archived, and my subsequent proposal (which I never got around to trying to implement -- I think you did a bit of it at some point, but matters are still not satisfactory).
The name "naive", for non-formalized set theory pursued at the research level, is bad because you don't expect active research to be "naive", even if we can then quibble about how some (by no means all) workers use the word in a non-pejorative sense.
Because of that, the division of content gives the impression that workers in set theory no longer accept that there is a clear intuitive notion of "set" to which the axioms must conform, and instead have adopted the axioms themselves as primary.
I have other objections to your formulation of "any collection of objects that satisfy a well-defined property", since according to the contemporary realist approach, the objects satisfying certain properties simply cannot be "collected" at all. That being the case, extensions of these properties do not enter into the "any collection of objects" part of the phrase, and so do not cause inconsistencies. What you really mean is more something like "given any well-defined property, the collection of objects that satisfy it", where the inconsistency can be traced to the existential import of the word the. --Trovatore (talk) 21:00, 19 April 2009 (UTC)
I want to temporarily ignore all philosophical issues to just look at the overall organization.
We did merge axiomatic set theory and set theory at some point. The basic stuff is in set (mathematics), which does seem to overlap a lot with the basic stuff here.
One option would be, then, to merge the elementary set theory from this article to set (mathematics) and then reduce this article to just discussing the various meanings of "naive set theory" and point the readers to the other articles for the actual material about sets. We could use Halmos' preface to explain what he means by "naive", and I have some other citations for the other sense. — Carl (CBM · talk) 22:19, 19 April 2009 (UTC)
I noticed in the archive someone pointed at fr:Théorie naïve des ensembles. The lede to that article does head in the direction I am proposing. But the google translation really butchers it. — Carl (CBM · talk) 02:32, 20 April 2009 (UTC)
I support the idea of making this article a discussion of the different meanings of Naive set theory, and leaving actual treatment of sets to set (mathematics). The duplicate content is unnecessary. Cliff (talk) 16:20, 4 May 2011 (UTC)

## Change operation into abstraction?

In section 1 paragraph 3 of the article, "As it turned out, assuming that one can perform any operation on sets without restriction leads to paradoxes such as Russell's paradox and Berry's paradox.", shouldn't the "perform any operation on sets" be "define sets by unrestricted abstraction"? voidnature 08:48, 19 June 2011 (UTC)

## Article Motivation

Am I the only person who thinks the motivation for this article existing is a little weak. I mean couldn't we have a naive version of every mathematical area. It just seems dumb to me. 128.187.97.19 (talk) 18:13, 19 March 2012 (UTC)

The motivation for this article is that there's something called naive set theory (e.g. ISBN 0387900926) and we're describing it.--Prosfilaes (talk) 22:49, 19 March 2012 (UTC)

## Gratuitous mention of "Boolean algebra (structure)"

In section "Unions, intersections, and relative complements", there is the sentence: "For any set A, the power set P(A) is a Boolean algebra under the operations of union and intersection."

Evidently this relates to the "Boolean algebra" structure, a relatively advanced topic. Readers of the current article are likely only to be familiar with boolean algebra (as in the Boolean algebra article), which is not the topic of this sentence, and will find this sentence confusing and in any case not useful. I suggest removal. Gwideman (talk) 00:24, 27 August 2012 (UTC)

## Thompson

== Revising Naive set theory == Thompson (Neil Thompson 'Resolving Insolubilia: Internal Inconsistency and the Reform of Naïve Set Comprehension' Philosophy Study 2012 (2) ( 6) 417-431)) has suggested a means of revising Naive set theory that limits set comprehension by excluding set comprehension of sets isomorphic to Russell's set. Thompson claims that all paradoxes (save for Burali-Forti's and Goldstein's set schema which are excluded directly as contradictory descriptions) can be resolved in this fashion. The result is claimed to offer an ontology nearly as rich as that of Naive set theory.

This section keeps getting added to the article. I feel it's undue weight on one article and that it's misrepresenting this attempt to work around Russell's paradox as something fundamentally different from Zermelo–Fraenkel set theory or Quine's New Foundations, which it's not.--Prosfilaes (talk) 01:26, 1 May 2013 (UTC)

I also note that Philosophy Study is a journal found at http://www.davidpublishing.com/journals_info.asp?jId=680 , that the other articles posted in it are not mathematical articles, and that the publisher is not one of high repute; cf. http://chronicle.com/forums/index.php?topic=81342.0 . It's not a journal MIT gets, which brings up the question of whether anybody else does, and if anyone has seen it in the field to critique it.--Prosfilaes (talk) 01:49, 1 May 2013 (UTC)

## First usage of ∈ – 1889 or 1888?

I just edited the article (see diff) and changed the date of the first usage of ∈ from 1888 to 1889 (found the later date here and in the book „Mengen – Relationen – Funktionen“ by Ingmar Lehmann and Wolfgang Schulz). The date 1888 was introduced with this edit 2003 by an IP. Is there any reference for the usage of ∈ before 1889? Greetings, Stephan Kulla (talk) 20:21, 21 April 2014 (UTC)

Although probably not a reliable source, Earliest Uses of Symbols of Set Theory and Logic agrees with you on the date. It also claims the earliest date for the symbol ∉ is 1939 by Bourbaki. --Mark viking (talk) 20:47, 21 April 2014 (UTC)

## Definition of "naive theory"

To "In the sense of this article, a naive theory is a non-formalized theory, that is, a theory that uses a natural language to describe sets." I say, every theory uses a natural language to describe something. The formalization is done in a natural language, so there is always a natural language used. When in a formalized theory "The words and, or, if ... then, not, for some, for every" are "subject to rigorous definition", they are rigorously defined in a natural language. Cantors definition was a try to rigorously define the word "set"! 93.197.6.222 (talk) 20:44, 3 May 2014 (UTC) Thomas Limberg (Schmogrow)

Why did you call it "naive set theory" before I changed it, when you wrote "In naive set theory, a set is described as a well-defined collection of objects.". This is not naive! It's good work. It states "well-defined" so your paradoxes don't take effect. I have the feeling, you don't see the forest because of all the trees. After I changed it, it is a formalization of the term set. It rigorously defines it. The Zermelo-Fraenkel definition with all its axioms is not nesseccary. This definition here is better cause it generalizes the "set"-term. 79.252.242.192 (talk) 02:41, 4 May 2014 (UTC) Thomas Limberg (Schmogrow)

FYI, I have reverted all your edits. You are trying to insert your own thoughts (and to name them after yourself) into Wikipedia articles. This is original research, which is not allowed here. YohanN7 (talk) 13:42, 4 May 2014 (UTC)
But Wikipedia is so easy to use. Why is it forbidden to make research on it? 79.252.242.192 (talk) 13:51, 4 May 2014 (UTC) Thomas Limberg (Schmogrow)
It depends on what you mean. If Wikipedia is your subject of research, nobody will stop you. If you research in some topic that has a Wikipedia article, then you cannot use that article to promote your own research. The material in these articles should be verifiable. This means that they should have reliable sources. Reliable sources are usually third-party journals or books that cite the original research, itself presumably published in a reliable source. (And no, Wikipedia articles don't themselves qualify as "reliable sources".) YohanN7 (talk) 14:04, 4 May 2014 (UTC)
And look, it's not like I've published a book with 300 pages here. My thoughts are very short. There are talk entrys which are much longer and you have probably read some of them. In my eyes it doesn't make a difference just because it's original research. Did the high degree academics forbid you to think on your own? Ohhhhh! Poor you! 79.252.242.192 (talk) 14:09, 4 May 2014 (UTC) Thomas Limberg (Schmogrow)
Please don't edit old comments of yours.
Original research made directly into articles is almost always pure BS. The rules are there to keep the BS away for the benefit of the readers and for the integrity of the articles. YohanN7 (talk) 14:19, 4 May 2014 (UTC)
Hm maybe, but with your attitude you make it impossible for me to win. And I can tell you I've never tried to do original research on WP before, so I think you should give me a chance. Let me reduce it to two very short questions: 1. Do you see, too, that it (the Limberg-definition) avoids the paradoxes, too? 2. And do you see, that it is a general definition in contrary to the Zermelo-Fraenkel theory? 79.252.242.192 (talk) 14:29, 4 May 2014 (UTC) Thomas Limberg (Schmogrow)
See, it's really not much to check. 79.252.242.192 (talk) 14:45, 4 May 2014 (UTC) Thomas Limberg (Schmogrow)

──────────────────────────────────────────────────────────────────────────────────────────────────── Greetings Thomas Limberg: Sorry to interrupt, but I thought I could help expand on some of what YohanN7 has said. It's true that Wikipedians at the WP:Mathematics project adhere to strong rules about what may be included and how well it must be cited. The level of caution used sometimes surprises newcomers in the way it seems to have surprised you. But trust us, this caution is for good reason.

One of the core ideas about Wikipedia is that it is an encyclopedia, and as such it should be founded upon reliable secondary sources. By reflecting such sources, this increases its reliability and insulates it from people abusing it as a means to promote themselves. If you are serious about making good contributions to Wikipedia, then surely you will recognize the wisdom in such precautions.

I know this can be difficult and/or frustrating at first, and a lot of us have passed through this phase of acclimating to the culture of editors here. It's not so bad after you get the hang of it :) In the meantime, please do not engage in making any more unconstructive remarks with other editors. (Again, I know this is sometimes easy to do :) ) You must remember that anybody can see what you're saying, and behaving so will ultimately attract negative attention from the community, and this can lead to inconvenient punishments, if bad behavior persists. Ok, that's all I have to say: good luck, and happy editing! Rschwieb (talk) 15:29, 4 May 2014 (UTC)

Yes, here: Gödel's incompleteness theorems. In fact, the very moment you claim you have a definition of set theory, free of paradoxes—as a consequence of the definition itself, your claim (if true) implies that your theory is inconsistent, able of proving 1 = 0, hence containing paradoxes. YohanN7 (talk) 21:15, 4 May 2014 (UTC)
Not the place to discuss it. This space is for discussing improvements to the article. Thomas, might I introduce you to the mathematics reference desk? You can ask questions there, and get pointers for clarification. --Trovatore (talk) 21:21, 4 May 2014 (UTC)
So you claim that out of the Limberg-definition follows that 1=0? Sorry, I can't follow you. I can't imagine how this could have been done. 79.252.242.192 (talk) 21:35, 4 May 2014 (UTC) Thomas Limberg (Schmogrow)
This is not the place to discuss it. So stop discussing it. Otherwise the section will be removed. See WP:TALK. --Trovatore (talk) 21:37, 4 May 2014 (UTC)
Oh, I am discussing improvements to the article! I said that every set theory uses natural language to describe sets. It is only then non-formal, when this natural language contains unclearances or even inconsistancies. So I will improve now the article. 93.197.8.254 (talk) 10:23, 5 May 2014 (UTC) Thomas Limberg (Schmogrow)
In section "Sets, membership and equality" you give an explanation of the "set"-term and you state that it is naive set theory. So I want you to show the reader at which point this explanation is unclear or even inconsistent. 93.197.8.254 (talk) 10:29, 5 May 2014 (UTC) Thomas Limberg (Schmogrow)
But since the explanation of sets you've given here is not the top of the ice mountain of "general" set definitions (that is how I would call it, in contrary to e.g. Zermelo-Fraenkel, which I would call "specific" or maybe "constructive"), I want you to use the Limberg-definition ("http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Mathematics#continuing_discussion_about_Naive_set_theory") instead, which just contains some improvements to the explanation here, and show that there are unclearances or even inconsistencies in it. 93.197.8.254 (talk) 10:39, 5 May 2014 (UTC) Thomas Limberg (Schmogrow)
You have to do something! YohanN7 is starting to insult me! He writes that when a theory is consistent then he can show that it leads to 1 = 0, though. That's so stupid! Stop him! ("http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Mathematics#continuing_discussion_about_Naive_set_theory") 93.197.8.254 (talk) 10:57, 5 May 2014 (UTC) Thomas Limberg (Schmogrow)

I can see that you are up to it again.

• From your edits, it is clear that you don't know what modern informal (naive) set theory is. It does not "allow" for inconsistencies or ambiguities. It can't just prevent them. It has absolutely nothing to do with formal or informal languages. But formal axiomatic theories cannot "prevent" all possible inconsistencies either (some are prevented), tough they can prevent ambiguities.
• It is not for me, or anyone else, to 'show that your theory is inconsistent. [You fail to understand that you can't show it to be consistent either (unless it is, in fact, inconsistent). But this discussion, as Trovatore has pointed out, doesn't belong here.]
• Your biggest mistake is that even if you were right, your material would not make it to the article. It has been explained to you why above. YohanN7 (talk) 11:02, 5 May 2014 (UTC)

Oh boy, what are you talking?! You wrote "From your edits, it is clear that you don't know what modern informal (naive) set theory is.". Maybe, I've just read the article in the hope you would explain it to me correctly. But it seems I've expected too much. The artiucle says "a naive theory is a non-formalized theory". Formal means that you rigorously define the terms you use. You prevent Inconsistencies and ambiguities. So non-formal means you couldn't prevent this to happen. So when I apply the explanation of "naive" from the article then my edits are correct. Furthermore, you wrote "But formal axiomatic theories cannot "prevent" all possible inconsistencies either (some are prevented)". Really? But when these formal axiomatic theories are inconsistent then you have to discard them and say that you are not able to define the "set"-term. 93.197.8.254 (talk) 11:36, 5 May 2014 (UTC) Thomas Limberg (Schmogrow)
Dear Thomas Limberg: Let's do our best to de-escalate the tone of the discussion. ThomasLimberg, you can rationalize your edits with your homemade reasons until you are blue in the face; however, none of it matters. Remember that we only reflect information from established sources, not from reasoning on our own. The quickest way to bring editors around to your side is to point to a strong reference (or better yet three such references) that support the idea you want to include. In the face of good references, your opponents will usually disappear, but if you continue to behave combatatively with editors, you will mainly gain opponents. These are all logical consequences, correct? Rschwieb (talk) 16:17, 5 May 2014 (UTC)
Oh no, you got it wrong! In that item that you answered on it was not about doing research. I was complaining about a logical inconsistancy in the article (and I can ask as well, where is the source of this statement). I didn't bring new ideas in the game, I was questioning existing ones. 93.197.8.254 (talk) 17:25, 5 May 2014 (UTC) Thomas Limberg (Schmogrow)

## Setting of naive set theory

I renamed the section "Requirements" to read as above.

Already present was remarks that naive set theory isn't necessarily inconsistent. I added a paragraph about axiomatic set theory not being necessarily consistent. This should remove the possibility of some (but far from all) misunderstandings.

It is probably too much to include statements to the effect that solely requiring a set theory (naive or axiomatic) to be well-defined isn't enough to ensure the existence of a consistent set theory, which seems to have been Thomas Limberg's motivation for his edits. It might, if formalized, produce a theory of something, but nothing as powerful as set theory (because Gödel says no). The place to discuss this is not here, I know, but Thomas Limberg's concern may have been for the best of this article, and I hope he thinks my last edit at least didn't make it worse. YohanN7 (talk) 21:33, 5 May 2014 (UTC)

"requiring a set theory (naive or axiomatic) to be well-defined isn't enough to ensure the existence of a consistent set theory", I've told you I don't insist on that. "which seems to have been Thomas Limberg's motivation for his edits", no that is not nesseccary for the motivation of my edits! I don't have to state that it's consistent. You're the one who states that it's naive. I want you to take over my little improvements, leave out the word "well-defined" and then you can say that it's a naive theory. Now that there is still the word "well-defined" in it, I wouldn't call it naive. That seems wrong to me! 93.197.47.238 (talk) 05:04, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
From one of your first posts;
...This is not naive! It's good work. It states "well-defined" so your paradoxes don't take effect. I have the feeling, you don't see the forest because of all the trees. After I changed it, it is a formalization of the term set. It rigorously defines it.... (my emphasis)
You have been insisting on your theory being consistent, free of paradoxes, all the way.
On the "naive" issue. You don't understand how the terminology is supposed to be used in this article. There is no correlation at all between "not well-defined" and "naive" and "inconsistent". You should read "naive" as "informal formal set theory". This is the message of the section. YohanN7 (talk) 12:30, 6 May 2014 (UTC)
Informal formal set theory is not a contradiction. Almost all of mathematics is written informally, but in a formalizable way. For a typical example, see Naive Set Theory (book).
Naive set theory is not necessarily inconsistent, it is just not axiomatic or "formal" in that it doesn't refer to a particular axiomatization – or is particularly concerned with the consistency issues.
Finally, I can see that you have gone back to your habits of editing old comments of yours and changing the meaning of what you have written earlier, denying what you have actually said. (And oh, the insults; if there weren't there to begin with, you add a couple later.)
I hope you realize that I'm being incredibly patient with you. Most others wouldn't put up with the "stupid, hallucinating, etc", and you would sure as hell be indefinitely blocked by now.
Advice: Don't address anyone else but me this way. YohanN7 (talk) 12:30, 6 May 2014 (UTC)
Informal formal set theory is a contradiction!!! The word formal and informal are commonly used words which are contradictory. You're unscientific again! When you use these words with a different definition, you have to refer to this definition somehow, e.g. by giving the source (before you use these words, not after it)! And formal and formalizable are two different things for me, too. Furthermore, "Naive set theory is not necessarily inconsistent,", it is according to the German Wikipedia. Sometimes I reedit my posts, but very quickly after I wrote them and I don't change the meaning later or add insults. You're lying again! 93.197.47.238 (talk) 13:37, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
You seem to be unaware of the fact that English words have different linguistic and mathematical interpretations. I don't have to give a source because this is assumed (by all reading this talk page) to be known. It is common practice i mathematics.
Formal and formalizable are indeed different things, linguistically and mathematically.
Wikipedia isn't a reliable source, not even the German version. The Germans have, on occasion, historically been known to be wrong, at least, they have failed to achieve final consensus about their POV.
Yes, you almost always change the meaning of your posts, mostly refusing to acknowledge what you have written, like in your last post in the reference desk (not a reply but a "reaction""). I was almost rolling off the floor with laughter.
Yes, you add insults to your comments later on, like the one above. (You have to produce a diff to see it, not gonna do that for you, but for anyone else that wants to see.)
And a fresh insult from you.
Do you still feel that we should name set theory after you? YohanN7 (talk) 14:08, 6 May 2014 (UTC)
There are mathematical words with a different meaning than the linguistic ones that are commonly known and accepted, like e.g. set. But I haven't heard of a commonly known and accepted mathematical meaning of formal or informal! They might be defined differently in different sources. In the wikipedia article about set theory you don't find an explanation of "formal set theory". It is not so common. So I expected the linguistic meaning.
What you write about that I would change my posts is just crap! You're hallucinating again! Yes I added the "You're hallucinating", but this is just 1 min after I posted the entry. You needed half an our to answer on my last post.
Crap or not: Do not ever go back and change your earlier posts for whatever purpose unless you sign it, making it a NEW post. This includes adding insults that you forgot to add the first time around. YohanN7 (talk) 11:03, 7 May 2014 (UTC)
"Do you still feel that we should name set theory after you?", I nevewr demanded that! You can improve the set definition in the article to the Limberg-definition and name it after me. That's all I wanted. 93.197.47.238 (talk) 16:29, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
Yes, I admit. All you wanted is to change Cantors definition of a set and name it after you. And, to note that your brilliant contribution gives a set theory guaranteed to be without paradoxes. (Quite humbly, you didn't want this set theory named after you.) But why should we? Have you been published and cited in scientific journals mora than Cantor? YohanN7 (talk) 11:03, 7 May 2014 (UTC)
I would even be stricter. I would define the word naive to refer to an inconsistent theory. When it's just ambiguous, some will say it's inconsistent, some will say you can't say that. When you can't say that it's inconsistent, why calling it naive? In fact it is defined like that in the German Wikipedia. Why do you use a different definition? The only use of natural language is definately not enough to call it naive since you can formulate ZF in natural language, too. So stop that! You see, in fact, you're the ones who are not enough into the topic! 93.197.47.238 (talk) 05:25, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
And now my conclusion of above is confirmed. I actually agree with you here. I don't like the usage of the terminology either. But the article reflects the de facto usage of the term in the English-speaking world. You can probably blame Paul Halmos and his Naive set theory for this. But believe me, the terminology introduced by you into the article, "Thomas Limberg (Schmogrow) set theory", would be even worse. YohanN7 (talk) 09:24, 6 May 2014 (UTC)
"But the article reflects the de facto usage of the term in the English-speaking world", maybe some stupid students or even very few scientists of the history use/used it like this. That doesn't matter. It's wrong so you have to change it! "the terminology introduced by you into the article, "Thomas Limberg (Schmogrow) set theory", would be even worse.", you didn't tell me, yet, what's wrong about the Limberg-definition! 93.197.47.238 (talk) 10:24, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
Let us not argue about the Limberg-definition for the moment. You know it can't go into the article by now, and you know why. Even if it were the Holy Grail of Mathematics, able to prove or disprove the Continuum Hypothesis as you have hinted it would, it wouldn't make the article, at least not for now.
Your other point, "It's wrong so you have to change it!" (the terminology) is something that should be taken seriously imo. I would have preferred to have an article (basically with the present content) called "Informal set theory", leaving a sidenote somewhere on the "Naive" alternative terminology. If, as you say, the German article treats "Naive" as "Inconsistent", then we have a cross-Wiki problem. YohanN7 (talk) 10:28, 6 May 2014 (UTC)
"You know it can't go into the article by now", it is in the article already (except some little improvements). If you don't wanna call it Limberg-definition, hm, then they can't refer to it. I guess I can't force it upon you, I just wanted to say, I would find it better. Let's go on. The German Wikipedia says, "Der Begriff „naive Mengenlehre“... . Wegen Widersprüchen, die sich in ihr ergeben...", which means (The term "naive set theory"... . Because of contradictions which occured in it...). I mean the article also says that not rarely the term naive is used differently from the German Wikpedia usage in math literature. But as I have pointed out, it's unserious and the German Wikipedia doesn't use it like that. 93.197.47.238 (talk) 11:19, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
I told you, I agree with you on this.
I have now addressed the "well-defined"-issue. I wrote a mini-section on it. Better now? At least the internal usage (in the article) of the terminology cannot be misunderstood. Removing "well-defined" all together is not and option, because the article is not an article on inconsistent theories. "Badly-defined" sets are not allowed in the naive set theory we speak of here.
It remains to clarify that Cantors version of set theory is an informal (called naive in the article) set theory, and not an known-to-be inconsistent set theory. YohanN7 (talk) 11:44, 6 May 2014 (UTC)
"the article is not an article on inconsistent theories", the German Wikipedia says that naive means inconsistent, and that's what I believe, too. If you still insist to not change your definition of naive in this article, then according to your definition, the "set"-term definition in the article is informal (in the sense of not containing formal axioms) and hence naive. But I've told you, that is unserious and (in my eyes) discrediting to e.g. the Limberg definition. Furthermore, "so this does not at all hamper the utility of naive set theory as compared to axiomatic set theory" (added mini-section) sounds good to me. 93.197.47.238 (talk) 16:04, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
Did you just say Furthermore, "so this does not at all hamper the utility of naive set theory as compared to axiomatic set theory" (added mini-section) sounds good to me.?
Wow!
Perhaps it would be tolerable to you to have different definitions of "naive" in German and in English. I agree with you that the English (mathematical) definition sucks. Not much to do about this though, since we are supposed to be reflecting what the English-speaking mathematical community (including "stupid students", "very few scientists of the history" and the like) think. They are supposedly in the majority, but I don't know. I am going to start a new thread right away. YohanN7 (talk) 17:14, 6 May 2014 (UTC)
To those scientists who define in their work the word naive like it was done here in the article: I define: Your work is crap! Now, YohanN7, tell me, are you sure, you still wanna consider these works for this article, since I have proven it to be crap? 93.197.47.238 (talk) 18:10, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
No no, Thomas, you have misunderstood again. You have not proven anything at all. Which "works" are you referring to by the way? YohanN7 (talk) 18:55, 6 May 2014 (UTC)
"You have not proven anything at all", don't you get it?! I've defined it so it's proven. "Which "works" are you referring to by the way?", OMG you're so lame! Is this discussion so exhausting for you that you can't read anymore?! 93.197.19.94 (talk) 03:24, 7 May 2014 (UTC) Thomas Limberg (Schmogrow)
Yes it is. I have never been nanny to a crank before. Now, which works are you referring to, and what definition are you referring to? YohanN7 (talk) 19:57, 6 May 2014 (UTC)
Now shut the hell up!!!!! (with your ongoing insults) I already had the feeling that you don't listen to me. How shall I discuss with you when you can't even read my posts?! "Now, which works are you referring to, and what definition are you referring to?", read my posts!!!!! It's all in there and easy to find. 93.197.19.94 (talk) 03:24, 7 May 2014 (UTC) Thomas Limberg (Schmogrow)
I'm the only one here actually listening to you. YohanN7 (talk) 10:14, 7 May 2014 (UTC)

Section "Note on consistency", "It does not follow from this definition how sets can be formed, and what operations on sets again will produce a set.". Yes it does. I can say for example: Let M be the set of the numbers 0 and 1. That's legitime by the definition. Where's the problem?! 93.197.19.94 (talk) 08:27, 7 May 2014 (UTC) Thomas Limberg (Schmogrow)

So far you have actually proved nothing, but read on.
Do you explicitly include axiom of pairing in your theory or do you prove from more primitive assumptions?
Do you explicitly include axiom of union in your theory or do you prove from more primitive assumptions?
Do you explicitly include axiom of your choice of ZFC axiom here in your theory or do you prove from more primitive assumptions?
Do you explicitly include ....?
For example, in your "theory", given my experience with you, I am guessing that you would say that, for instance, the axiom of choice is obviously true. I'm afraid that this will not pass as a proof. You must formalize them, using basic assumptions (using your "definition of "set" presumably) only. Then they will be proofs. YohanN7 (talk) 10:14, 7 May 2014 (UTC)
If you don't explicitly include any axiom of ZFC and manage to explicitly prove all of them, then I congratulate you. The only real problem for your theory is that Gödel's incompleteness theorems then shows that your theory is inconsistent. Not maybe inconsistent, but definitely inconsistent.
Do you now see? A positive proof of yours will only ruin your theory. YohanN7 (talk) 10:14, 7 May 2014 (UTC)
Finally, if you miraculously manage to prove Gödel wrong, then your theory still don't qualify for inclusion in Wikipedia because it would be original research. This is back to square one. This is what has been patiently explained to you over and over, by me and others. During the process, you have spewed bad language, mostly at me (which is the reason you are still not blocked, because I can take it), but also at others, firmly refusing to acknowledge anything someone tells you. This is why I call you a crank (person). You qualify as a crank. This is semi-insulting, but considering that it is provably true(our conversation proves it), and considering what you have called me (stupid, hallucinating, retarded, ...), I don't have second thoughts about it. YohanN7 (talk) 10:14, 7 May 2014 (UTC)

## Proposed move

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: No move. While there are many things in this rather complex discussion which are anything but clear, one thing which is certainly clear is that there is no consensus to move, and there is substantially a consensus not to move. The editor who uses the pseudonym "JamesBWatson" (talk) 10:25, 15 May 2014 (UTC)

Naive set theoryInformal set theory – How about renaming this article to "Informal set theory" (and editing it appropriately)? I myself neither "support" nor "reject". I can see good arguments for both options. YohanN7 (talk) 17:18, 6 May 2014 (UTC)

(I converted this proposal into a Requested Move so that it will be listed in WP:RM. I have no opinion on the move myself. EdJohnston (talk) 23:11, 7 May 2014 (UTC))
"Naive set theory" seems to be used more frequently than "informal set theory". A redirect is certainly useful, though. --Anagogist (talk) 18:55, 6 May 2014 (UTC)
Perhaps true. The German Wikipedia (according to a friend of mine, "Thomas Limberg" of above) claims Naive set theory ⇔ Inconsistent set theory (in German and in German Wikipedia). YohanN7 (talk) 19:00, 6 May 2014 (UTC)
According to Google Translate, naiv in German means naive in English, so I don't think we have stumbled upon a case of false friends. Although this set theory is definitely inconsistent, it is "naive" as well in the ordinary sense of the word (what is trying to build the foundations of mathematics upon natural language if not naive?), and so it seems to me that the name of the article captures the spirit of its subject. --Anagogist (talk) 19:12, 6 May 2014 (UTC)
Linguistic interpretation may well differ from mathematical interpretation. The set theory referred to in this article is not definitely inconsistent. YohanN7 (talk) 20:11, 6 May 2014 (UTC)
I would say, too, that it's not a false friend. "Although this set theory is definitely inconsistent", what? Which set theory? The one in the article? No, it's not inconsistent. Is it? Then show it! I knew it, people think, a non-fomal definition automatically leads to one of the known paradoxa. It's becouse in certain books naive is defined as non-formal, like in this article, too. That is misleading!!!!! Thomas Limberg (Schmogrow) (talk) 09:08, 7 May 2014 (UTC)
I typed "inconsistent" instead of "informal". My sincerest apologies. --Anagogist (talk) 11:52, 7 May 2014 (UTC)
(ec) Limberg's assertion does not accord with my reading of de:Naive Mengenlehre. I read that article as saying that informal set theory can lead to the classical antinomies because the notion of set is insufficiently well-controlled. Deltahedron (talk) 19:16, 6 May 2014 (UTC)
Actually the article doesn't even contain the word "informal". If you meant "naive" then what you read is that what I read. 93.197.47.238 (talk) 19:41, 6 May 2014 (UTC) Thomas Limberg (Schmogrow)
It does contain the word "informal". If moved, "naive" would be changed to "informal" in several places. YohanN7 (talk) 20:11, 6 May 2014 (UTC)
We are talking about the German article. 93.197.19.94 (talk) 03:18, 7 May 2014 (UTC) Thomas Limberg (Schmogrow)
It contains the phrase eine unformalisierte axiomatische Mengenlehre. Deltahedron (talk) 20:01, 6 May 2014 (UTC)
Oh, sorry I thought about the translation "informell" or something. Anyway, in that case: Of course an informal set theory can lead to antinomies! But I didn't question that. I talked about naive set theories! 93.197.19.94 (talk) 03:18, 7 May 2014 (UTC) Thomas Limberg (Schmogrow)

As I see it, there are various competing narratives, and the problem with the locution naive set theory is that it is not really neutral among them.
First, there are two views about the source of the classical antinomies:
1. The classical antinomies derive from insufficient formalization
2. The classical antinomies derive from a error in the informal conceptualization (for example, conflating the intensional and extensional notions
A related, but distinct, dimension of the question is the status of Cantor's theory:
1. Cantor's informal theory leads to the antinomies
2. Cantor's informal theory, at in its least the more sophisticated later versions, does not lead to the antinomies
Unfortunately, the typical usage of the term naive set theory assumes the first position in both of these controversies. That does not by itself exclude having an article at the title naive set theory, but if we do, we should be very careful to give a balanced account, and emphasize the controversies right up front. Moving the article to informal set theory might in fact make the balancing act easier; not completely sure what I think about that yet. --Trovatore (talk) 20:21, 6 May 2014 (UTC)
Not that my voice carries a lot of weight - but, I do not believe the page should be moved to "informal set theory". "naive set theory" seems to be more common, is the term used to refer to the informal theory in the beginning of a lot of text books (I personally have over 1500 mathematics text books, a bulk of the introductory ones start with a chapter mentioning "naive set theory" somewhere), and - on less sure footing - while "informal" is perhaps more descriptive, "naive set theory" seems to function as a label for a specific conception of informal sets -- as to say that the "naive" in "naive set theory" is not descriptive, at this point, so much as it is part of a common label for a common construction; thus, even if "informal" is the better word, it still shouldn't apply (anymore than we should move the article "driveway" to "parkway" because "park" is more descriptive).Phoenixia1177 (talk) 00:33, 7 May 2014 (UTC)
I do agree that it's probably more common. But is it more common as a description of one particular thing? The term carries a lot of baggage, and exactly what baggage depends on who's using it.
I think it's likely that the most usual sense in which naive set theory is used is as a description of this supposed inconsistent informal set theory that Cantor supposedly had in mind. This fits neatly into the narrative that the solution to the antinomies was formalization — so neatly that I think it's a challenge to give sufficient weight to the counternarrative of (for example) Wang Hao, in an article titled naive set theory. Not that it can't be done, necessarily. But I think it might be easier to give a balanced presentation under the title informal set theory.
Now, some may disagree that the sense I have described is in fact the most common usage — some may say, no, "naive" is not intended pejoratively and does not need to refer to an inconsistent theory; for example, Halmos certainly did not intend it in the sense of a theory that he thought was inconsistent.
Fine, but doesn't that make the title even more problematic? In that case, it's not a description of an agreed-upon, well-specified topic, but simply a locution that different authors have used in different ways. --Trovatore (talk) 01:14, 7 May 2014 (UTC)
I've always taken the "naive" in the same sense as the word "real" in "real number" - and in a slight analogy, exactly what is meant by the "real numbers", exactly, can vary or have different degrees of baggage in certain contexts. On the subject of "used in different ways", that may very well be the case, but I'd see that more, to use a vague analogy (that nonetheless works for me), to be in the same way there are various non-Doyle Sherlock Homes stories: each uses the character, setting, traits, etc. in different ways, but they all share a common thread that makes them about the same entity (I realize that's not the most clear - it's about two hours past my bed time). As for "informal set theory", I don't like using it since "informal" is, seemingly, fully descriptive, not naming, and there are things that could be informal set theories that I don't think would ever pass as "naive set theory" -- suppose you informally started with some basic notion of categories and got something equivalent that way (you could), this would not be "naive set theory" even if it gave the same end results. But, even if we are taking "naive" to be descriptive, I would say that it means "naive" as in "reasoning about collections from our very limited intuitive position" not as in "reasoning informally about collections", even though both are informal, the former is far more concerned with the way in which sets are treated as if they were the small definite sets we are generally accustomed to --
in that vein, but off topic, I'm not fond of the sentence "The choice between an axiomatic approach and a naive approach is largely a matter of convenience. In everyday mathematics the best choice may be informal (naive) use of axiomatic set theory, with references to particular axioms and/or formal proofs when tradition (the axiom of choice is often mentioned when used) or exceptional circumstances warrants it." in the article, the use of "naive" in parentheses seems both to over accentuate the descriptive sense and to use it in a sense that I do not believe is exactly intended. Finally, could you elaborate on Wang Hao? I'm not greatly familiar with him and am not making the connection. -- I apologize if any of my points seem off, I don't feel I'm presenting things well:-) Phoenixia1177 (talk) 03:01, 7 May 2014 (UTC)
Regarding the quote you gave in the last paragraph: When I wrote that I (subconsciously?) used naive and informal as being synonymous. Thank you for pointing it out, because (Halmos' influence?) that is the way I usually think about the matter. This is internally consistent with the usage of the terminology within the article as it stands, but it may be wrong. Suggestions? YohanN7 (talk) 18:00, 7 May 2014 (UTC)
@YohanN7: It would appear that that usage of "naive" is consistent with Halmos, but I think it would be good to separate the term "naive" from the term "informal". In the context of Halmos, and this article, they are equivalent, but in a larger sense, I can conceive of things that would qualify as both being informal and set theory, but are not anything like what appears here. My only suggestion would be to consider "naive" as part of the name "naive set theory" and not an adjective that describes what is presented (in any sense), and, then, to just use "informal" where the word describes the situation at hand - though, it would still make sense to explain the motivation for the word "naive" ending up in the name, I don't think we should use that word as a descriptor (in the same way we could explain why the reals are called the "reals", but shouldn't apply that word to them as an actual adjective). --
On an aside, would it be okay I modified some of the language used to enhance readability/flow? For example changing "The symbol ∈ is a derivation from the lowercase Greek letter epsilon, "ε", introduced by Giuseppe Peano in 1889 and shall be the first letter of the word ἐστί (means "is")." to "The symbol "∈", introduced in 1899 by Giuseppe Peano, is a stylized version of the Greek letter epsilon, the first letter of the word ἐστί (meaning "is").", and other such that doesn't alter the meaning. I mean no disrespect to the original writer - mine may be worse, just personal preference.Phoenixia1177 (talk) 01:08, 8 May 2014 (UTC)
Naturally, go ahead and edit. This is Wikipedia. Besides, I've only been involved in this article for a couple of days. (It wouldn't matter if it were 15 years.) I'll try to comment on the more complicated issues later on. YohanN7 (talk) 09:11, 8 May 2014 (UTC)
I gave it a try. Better? YohanN7 (talk) 10:57, 8 May 2014 (UTC)
I believe that "naive set theory" is the standard term for this subject, though I would be interested in references that said otherwise. Ozob (talk) 01:16, 7 May 2014 (UTC)
The standard name for what subject? That's a big part of the problem.... --Trovatore (talk) 01:23, 7 May 2014 (UTC)
The subject described by the present article: Naive set theory is set theory stated non-formally. Regardless of how one interprets the adjective "naive", and regardless of the actual content of the theory, the theory is named "naive set theory". To draw an analogy: A vector is normal to a surface if it is perpendicular. Does being "normal" mean that such vectors are ordinary? Nevertheless such vectors, rare though they might be, are called normal. Ozob (talk) 03:55, 7 May 2014 (UTC)
So the problem with presenting that topic under the title "naive set theory" is not about the word "naive" per se; it's about overweighting the formalization-was-the-cure-for-the-antinomies narrative I mention above. As I say, it may be possible to give a balanced treatment even with that title, but it seems to me that there's already a strike against it that might not be there with the other title. --Trovatore (talk) 04:36, 7 May 2014 (UTC)

I personally would be against such a move. While we may have Halmos to blame, it is a very standard phrase. I agree it can be a bit ambiguous, bet we should deal with the ambiguity instead of cooking up a new title. Thenub314 (talk) 04:55, 7 May 2014 (UTC)

Hmm, well, it certainly looks like the idea's not getting much traction. I'm a little disappointed; in spite of the unfortunate circumstances, I thought the idea had some real possibilities. But I suppose the main thing is to make sure we present a balanced account, under whatever title.
Looking it over, it's not too bad. The first real problem I see is in the third paragraph of the "setting" section, and I have already addressed one complaint about that section simply by changing "the" to "a".
Some things I would like to see addressed, in no particular order:
1. Some sort of discussion on the extensional versus intensional conceptions. The antinomies really only attach when you mix the two up. Whether Cantor did that is somewhat of an unsettled question.
This may now be partially addressed as a consequence of addressing item 3 below. YohanN7 (talk) 12:41, 8 May 2014 (UTC)
2. Some discussion of Halmos' usage of the term, which seems to be quite different from anything currently treated in the article (I haven't actually read Halmos' book, but from what I have read about it, Halmos actually presents a fully axiomatic theory, and I don't think it's one that admits the antinomies).
It doesn't. He presents ZFC except perhaps for the axiom of regularity. Regularity is "almost there" by exclusion of sets that are elements of themselves. (Disclaimer:From memory) YohanN7 (talk) 18:18, 7 May 2014 (UTC)
Halmos writes in the Preface to Naive Set Theory: In set theory "naive" and "axiomatic" are contrasting words. The present treatment might best be described as axiomatic set theory from the naive point of view. It is axiomatic in that some axioms for set theory are stated and used as the basis of all subsequent proofs. It is naive in that the language and notation are those of ordinary informal (but formalizable) mathematics Paul August 19:57, 7 May 2014 (UTC)
3. The third paragraph of the "setting" section actually does have another problematic part, the line [a]s it turned out, assuming that one can perform any operation on sets without restriction leads to paradoxes such as Russell's paradox and Berry's paradox. But, well, first of all Berry's paradox is out of place here (it's a paradox about definability, not about sets), and more important, you don't get Russell's paradox by allowing "operations without restriction", whatever that means, but by assuming that every predicate has an extension. This should be cleaned up.
This specifically has more to do with "unrestricted comprehension", right? YohanN7 (talk) 18:42, 7 May 2014 (UTC)
I gave this a try as well. YohanN7 (talk) 12:34, 8 May 2014 (UTC)
4. The "note on consistency" in the "sets, membership, and equality" section implicitly imputes to Cantor's "gathering together into a whole" definition a particular meaning, which may not have been the one Cantor intended. If you read Cantor's Beiträge as translated by Philip Jourdain (Contributions to the Founding of the Theory of Transfinite Numbers), that definition comes to look much less like extensions of arbitrary predicates, and much more like something prefiguring the iterative hierarchy. (The other side of that, though, is that while the Beiträge was written well before Russell, Jourdain's translation was significantly after the RP, and I am too lazy at the moment to strain my pitiful German trying to compare Contributions with Beiträge to see how much it might have been adapted after-the-fact.)
The whole section Notes on consistency was written with "a set is described as a well-defined collection of objects" appearing earlier in mind, not Cantor's verbatim definition. This is admittedly a problem. This article treats (at least) three things; Cantor's original theory/Naive set theory (whatever it might be)/Informal set theory. YohanN7 (talk) 20:35, 7 May 2014 (UTC)
I'd like to add, as well, that writing that section based on Cantor's words alone is extremely difficult. What exactly did Cantor have in mind? The "well-defined" clause of our (home-made?) definition, does at least provide some clue as to what is meant. YohanN7 (talk) 20:42, 7 May 2014 (UTC)
I gave it a new try. YohanN7 (talk) 11:57, 8 May 2014 (UTC)
Any thoughts on any of these? --Trovatore (talk) 07:01, 7 May 2014 (UTC)

In my opinion, the people (except maybe some very neutral and serious) mathematicians are not able to disconnect the linguistic meaning of naive from the meaning in this article. To make a compromise, you can call the article "naive set theory", but when you write "In naive set theory..." about the set definition in the article, then I want you to give a hint exactly at that spot where the word naive appears like "in the sense of this article"! The purpose of the mathematical definition of the word "naive" was to refer to the paradoxes they've found. Some people may have thought that all informal or non-formally-axiomatic set theories would lead to paradoxes. And (formally) axiomatic set theories like ZFC were the Holy Grail. But that's not true! 93.197.19.94 (talk) 07:32, 7 May 2014 (UTC) Thomas Limberg (Schmogrow)

When the majority of the scientists says that "2+2ǂ4" then will you write it in the Wikipedia? At least write it as a citation like "the majority of the scientists says that "2+2ǂ4"". I told you already, you let some academics forbid you to think on your own. You are followers. Thomas Limberg (Schmogrow) (talk) 09:37, 7 May 2014 (UTC)

If the majority of scientists for some reason decided that the symbol "4" should not be used for the natural number between 3 and 5, then yes, we would write it on Wikipedia. You say this, but then you say "you let some academics forbid you to think on your own"; think about what? The theory? This discussion has not been about the theory, it has been about terminology (the best name for the article). Would we be "blindly following" scientists if we used electromotive force to refer to the voltage of a battery (even though the name is misleading)? --Anagogist (talk) 11:59, 7 May 2014 (UTC)
When I look at it very principially, then you're right of course, but every idiot knows that 2+2=4 and normally everyone who would say that e.g. at school would be considered to be a total retard. Only when scientists say that, then you find ways how it could be true anyway. In fact, I didn't say that I would in any way redefine anything. And that has never been my intention!!! (I always work very scientifically, in my opinion. If I wanted any redefinition I would've said that!). So it should be clear now what I mean. Thomas Limberg (Schmogrow) (talk) 12:20, 7 May 2014 (UTC)
Ok, let me put it this way: If the majority of the scientists (on a certain field) would define "you're an asshole" ("you" refers to the reader of this post), would you write it into Wikipedia? OMG lol! Just asking a scientific question! lol! Thomas Limberg (Schmogrow) (talk) 12:25, 7 May 2014 (UTC)
Being your nanny Limberg, I have to warn you. You are insulting someone else but me. That is a no-no. YohanN7 (talk) 12:31, 7 May 2014 (UTC)
Calm down, YohanN7, you're slow on the uptake again, I say it again: It's nothing but a scientific question, in fact. Thomas Limberg (Schmogrow) (talk) 12:41, 7 May 2014 (UTC)
It is utterly unclear to me what you mean. Let's take a step back; what is your issue with the name of the article as is? Trovatore above made some very salient comments about the source of the antinomies in the theory and argued that the title "naive" may give weight towards the view that their source is lack of formalisation (as opposed to unformalised conceptualisation). The counterargument is that we don't shouldn't move the article (since "naive set theory" is used much more widely than "informal set theory"), but we can rectify the issue by drawing the distinction between the two viewpoints. I'm largely in favour of the latter because it follows WP:COMMONNAME (following what I said earlier, nobody is suggesting that we change the title of electromotive force and we can clear up any conceptual issues without needing a move. --Anagogist (talk) 12:38, 7 May 2014 (UTC)
Don't you get it? The point is: When this article is seen to not insult the Limberg set definition (to be naive), then I couldn't be seen to have insulted you (the reader) (to be an a**hole). Thomas Limberg (Schmogrow) (talk) 12:47, 7 May 2014 (UTC)
Anagogist, I can tell you, YohanN7 told me, when I don't understand anything, then I shall read it again and again and again and again and again! Thomas Limberg (Schmogrow) (talk) 12:53, 7 May 2014 (UTC)
I don't know, what you're up to, I'm still here, so I give you some time to answer (if you want to answer). See you in a while! Thomas Limberg (Schmogrow) (talk) 13:00, 7 May 2014 (UTC)

To those of you yet unfamiliar with Limberg, he introduced himself into Wikipedia with this edit: [1]. He humbly suggests makes it a fact that Cantors definition of set should be modified and christened with a name, the "Thomas Limberg (Schmogrow)-definition". YohanN7 (talk) 13:03, 7 May 2014 (UTC)

So what shall that mean? Shall I go on waiting for reactions or just move on? Thomas Limberg (Schmogrow) (talk) 13:11, 7 May 2014 (UTC)
Dear Thomas Limberg: Please don't add lots of irrelevant text to the talkpage. Disruptive editing is not prohibited only in the articles: it is prohibited everywhere. Thanks. Rschwieb (talk) 17:02, 7 May 2014 (UTC)
Actually, I asked for reactions, but noone said anything against it (until now), so I thought, maybe it's interesting. And in fact, there was a serious question in it, but when you don't wanna hear it, ... Thomas Limberg (Schmogrow) (talk) 17:40, 7 May 2014 (UTC)
The question was: I'm thinking about, if it's possible, that someone (maybe state organisations who work secretly (like e.g. secret services or the military)) developed drones or sattelites, with which they can shoot invisible rays (electromagnetic or radioactive) on innocent citizens. Do you think that is possible? Thomas Limberg (Schmogrow) (talk) 22:28, 7 May 2014 (UTC)
Furthermore, I din't get an answer on my question "Ok, let me put it this way: If the majority of the scientists (on a certain field) would...", yet. So would you, please? Thomas Limberg (Schmogrow) (talk) 17:42, 7 May 2014 (UTC)
Ok, this conversation is getting a bit heated. To consider a question posed earlier. It is in fact the case that the majority of scientists (if you include mathematicians as scientists, but we don't use anything as weak as the scientific method) do in fact consider me an asshole. But I would not put that on wikipedia, there is a clear COI violation, which is particularly serious in the BLP arena. I would not however object to it being included in Wikipedia, if it can be verifiably sourced. Thenub314 (talk) 17:50, 7 May 2014 (UTC)
"do in fact consider me an asshole", in the linguistic or the mathematical sense? Furthermore, you say, that you wouldn't put it on Wikipedia, but you wouldn't mind others to put it on Wikipedia. That's so funny, hahahahahahahahahahahahaahahahah!!! You would let them call you an asshole?! lol lol lol!!! Thomas Limberg (Schmogrow) (talk) 18:23, 7 May 2014 (UTC)
"this conversation is getting a bit heated", maybe it's because maybe someone is heating me with evil invisible rays! My health is doing worse and worse, so I have to hurry to do everything that I wanted to do in my life. And solving the problem of the term "naive" in naive set theory belongs to it. Thomas Limberg (Schmogrow) (talk) 18:38, 7 May 2014 (UTC)
• Procedural note: Unless the editors object, I will add a {{Requested move}} header at the top of this discussion so it will be entered on the Wikipedia-wide listing of proposed moves at WP:RM. That will encourage outside opinions and will allow a formal closure after seven days (i.e. as early as May 13). Thank you, EdJohnston (talk) 18:46, 7 May 2014 (UTC)
What, you want my opinion? "encourage outside opinions", sounds good to me. Thomas Limberg (Schmogrow) (talk) 19:41, 7 May 2014 (UTC)

See you tomorrow! Thomas Limberg (Schmogrow) (talk) 20:25, 7 May 2014 (UTC)

• Oppose move. Google scholar has 46 scholarly publications with "naive set theory" in their titles, and only one with "informal set theory". That seems pretty definitive to me about which of these phrases is in common usage. I don't put a lot of weight on the argument that the current title hurts the feelings of naive set theorists. —David Eppstein (talk) 01:22, 8 May 2014 (UTC)
I hope you're not characterizing my argument that way. I'll assume you're talking about Limberg's views. In any case, while I think the move would probably be an improvement, the writing on the wall is clear, and I would prefer to close this discussion and refocus on how to avoid or mitigate the potential harms of the title, which have nothing to do with "hurt feelings". --Trovatore (talk) 01:58, 8 May 2014 (UTC)
I didn't complain about the title, actually, but about the definition of "naive" in the article. Change it to "naive" meaning "inconsistent", like it already is in the German Wikipedia! And you can add an article "informal set theory". Thomas Limberg (Schmogrow) (talk) 07:39, 8 May 2014 (UTC)
• Support move. The usage count of the two terms is compensated for by the fact that "Naive set theory" means several different things, including informal axiomatic set theory, which is the main thrust of the current article, and simply inconsistent (non-)theories. The influence of Halmos and others, naive ⇔ informal axiomatic, is probably still quite strong on the use of terminology among mathematicians, so that choice main thrust can't be wrong. With "Informal set theory", the title would unambiguously reflect the main subject of the article, whatever colloquialisms (locutions or whatever) people may use for it. The naive ⇔ inconsistent interpretation is out of the question (in the English-speaking world), since it would not reflect an anywhere near universal agreement, just like Cantor set theory ⇔ inconsistent would be simply wrong. Cantor's theory is often called naive, but better is having it called informal (since it can't be misunderstood, while "naive" could). YohanN7 (talk) 10:24, 8 May 2014 (UTC)
YohanN7, just to be clear, every set theory is axiomatic, since it contains a definition (of the word set). And every (non-empty) definition has at least one axiom. A definition is (by definition) a set of axioms (and maybe some additional explanation or somewhat). So every informal set theory is an informal axiomatic set theory. YohanN7, really! You make it so hard for me to discuss with you! About your "universal agreement": Name me the main distributors (or proposers, whatever translation you prefer) of the definition naive meaning informal! 93.197.37.73 (talk) 13:05, 8 May 2014 (UTC)
Thomas, you have an account. Why don't you use it?
The main distributor of naive meaning informal is probably Paul Halmos with his Naive Set Theory (book). You should read it. I don't know of any modern book in set theory introducing naive set theory as anything else than informal axiomatic set theory. There is little point for a mathematician today to produce anything else, since axiomatization has been found necessary in order to avoid known paradoxes.
An informal definition of "set" is not axiomatic. The informal definition of, for instance, Cantor can be axiomatized in many many different ways, yielding different theories with different universes and different theorems, all possibly consistent, and in accord with the informal definition of "set".
No axiomatic set theory formally defines "set" as a primitive. It is left undefined.
Thus, "set" is not formally defined, either in informal or in axiomatic set theories. YohanN7 (talk) 14:04, 8 May 2014 (UTC)
"Thomas, you have an account. Why don't you use it?", I don't know it either, I somehow got logged out whithout notice. Thomas Limberg (Schmogrow) (talk) 16:16, 8 May 2014 (UTC)
Reedit: Since this Wikipedia article says the definition of sets that it contains was naive (by definition), I hereby define, this Wikipedia article is crap! Thomas Limberg (Schmogrow) (talk) 20:47, 8 May 2014 (UTC)
Look at it from the bright side. Your definition (according to Halmos) is informal, but is in no way necessarily inconsistent. It is just not a precise formal definition. For that you need to, at the very least, axiomatize your theory. YohanN7 (talk) 22:01, 8 May 2014 (UTC)
Thomas, again you have changed the meaning of your posts by editing it. Don't you understand? It is a no-no. I have replied to the previous version of your post. This is something that you probably (if I know you correctly) will make use of. YohanN7 (talk) 22:20, 8 May 2014 (UTC)
I can change it so I do it. The previous version may have been inappropriate. What speaks against that?! Thomas Limberg (Schmogrow) (talk) 22:43, 8 May 2014 (UTC)
Are there other things that you can do and therefore do?
You have been complaining sometimes that people don't reply to your posts. Do you think they will reply when there is a fair chance that you will change your post to mean something completely different? YohanN7 (talk) 23:11, 8 May 2014 (UTC)
"You have been complaining sometimes that people don't reply to your posts.", no I didn't. Thomas Limberg (Schmogrow) (talk) 23:25, 8 May 2014 (UTC)
Damn it, it happened again. I got logged off suddenly without telling me. Thomas Limberg (Schmogrow) (talk) 22:43, 8 May 2014 (UTC)
I'm wondering too why you think that I make it particularly hard for you to discuss with me. Think about it. I'm the only person around here actually discussing with you. You have no reference frames, and can't say I'm particularly hard to discuss with – as compared to anyone else. Can you figure out why nobody else discusses with you? YohanN7 (talk) 15:50, 8 May 2014 (UTC)
I agree with you that the term "naive set theory" can mean several different things. But I think it's essentially because of history, not because two wholly distinct subjects were accidentally (or maliciously) given the same name. Set theory started with natural language definitions because that's what everyone of that era used. As it evolved it gradually became axiomatic, and I'm sure that the term "naive set theory" first appeared among practitioners of axiomatic set theory because they needed to distinguish their approach from earlier ones. Since axiomatic set theory came to dominate, the term "naive set theory" evolved: Rather than distinguishing historical versus contemporary research, it distinguishes two viewpoints on the same subject.
Naive set theory refers, in addition to informal axiomatic set theory, also to Cantors non-axiomatic theory (and other), as well as to definitely inconsistent theories (German Wikipedia according to Thomas Limberg).
In addition to that, I would say that if you want an article on "informal set theory", then you will need references that prove that the latter term is in use. As always, verifiability on Wikipedia is non-negotiable. Ozob (talk) 13:58, 8 May 2014 (UTC)
Certainly. But there is no rule to say that the term must be the most common one. Usually this would have to be so. But in the present context, since the term "naive" is so blurred, we can make an exception. It will certainly make it easier to write a good article, without having to constantly write "disclaimers" (e.g, here "naive is to be interpreted as ...) YohanN7 (talk) 14:26, 8 May 2014 (UTC)
WP:COMMONNAME says, "Wikipedia prefers the name that is most commonly used (as determined by its prevalence in reliable English-language sources) as such names will be the most recognizable and the most natural." So unless there is a movement for "informal set theory" that I'm unaware of, it seems that the current title should remain "naive set theory". Ozob (talk) 01:40, 9 May 2014 (UTC)
You didn't read the preceding discussion. The question was not if to rename the article, but if to add a new one with the name "informal set theory". And if to change the definition of naive in this article (to inconsistent instead of informal). Hope it is clear now to everyone here. Thomas Limberg (Schmogrow) (talk) 03:49, 9 May 2014 (UTC)
@Ozob: "... the most recognizable and the most natural." I don't see naive set theory as a "natural" name for (what subject?). Therefor an exception is, at least, possible. Only in this thread there is wild disagreement on what the subject "naive set theory" is. The article is almost exclusively on informal set theory, which is a well-defined topic (commonly called so or not). But I'm not insisting, I was neutral for a start, but somewhat tilted over to my present vote after reading Trovatores posts. YohanN7 (talk) 10:14, 9 May 2014 (UTC)
The exact phrasing uses "the most recognizable and the most natural" a justification for the actual rule, which is "the name that is most commonly used (as determined by its prevalence in reliable English-language sources)". If we could go back in time and change historic usage, I too would prefer the name "informal set theory". But since Wikipedia is only supposed to report the usage of reliable sources, I think we're forced to use "naive set theory". Ozob (talk) 13:46, 9 May 2014 (UTC)
Holy shit! We use it so it is in use! Thomas Limberg (Schmogrow) (talk) 22:43, 8 May 2014 (UTC)
Thomas, you are about one millimeter from getting yourself blocked. If that happens, what would you do tomorrow? Save yourself that! (And have a look at your talk page.) YohanN7 (talk) 22:59, 8 May 2014 (UTC)
Very astonishing! I don't see I did anything wrong. You have to explain that to me. Thomas Limberg (Schmogrow) (talk) 23:19, 8 May 2014 (UTC)
You aren't answering to me. You are answering to somebody else. Have you checked your talk page? Do you realize that you are about to be thrown out? YohanN7 (talk) 23:32, 8 May 2014 (UTC)
I didn't answer because I thaught it was irrelevant (and keep on thinking so). Furthermore, who would want to block me? I didn't get any warning yet! Thomas Limberg (Schmogrow) (talk) 23:47, 8 May 2014 (UTC)
Just write the article, and more and more people will overtake this usage. Thomas Limberg (Schmogrow) (talk) 23:21, 8 May 2014 (UTC)
And they know your ip's. Taking your own hobby away? Smart! YohanN7 (talk) 23:01, 8 May 2014 (UTC)
What?! Which hobby? I don't understand it. Thomas Limberg (Schmogrow) (talk) 23:21, 8 May 2014 (UTC)
This hobby.
You logged in and went back and signed? Told you, not good. YohanN7 (talk) 23:32, 8 May 2014 (UTC)
I already told you twice, sometimes the system suddenly throws me out without warning! Shall I not sign at all?! Or what?! See! You're the one who doesn't deal with the other ones posts! You're an egocentric person! Thomas Limberg (Schmogrow) (talk) 03:54, 9 May 2014 (UTC)

See ya tomorrow! Thomas Limberg (Schmogrow) (talk) 23:48, 8 May 2014 (UTC)

Note: for what it's worth, Thomas Limberg (Schmogrow) (talk · contribs) has been blocked indefinitely for WP:NPA violations and other reasons. --Kinu t/c 05:00, 9 May 2014 (UTC)

Removing comments that were posted by User:Thomas Limberg (Schmogrow) via block evasion. --Kinu t/c 17:17, 9 May 2014 (UTC)
• Oppose move. "Naive set theory" is the term of art. Deltahedron (talk) 17:40, 11 May 2014 (UTC)
• Oppose move. Naive set theory is the normal name for this, both historically and in current work. The meaning of informal set theory has subtle but important differences. Andrewa (talk) 00:01, 15 May 2014 (UTC)
• Oppose move — please close. Doesn't address the real issues anyway. Let's close this and refocus on the real issues. Please see my new section at the bottom. --Trovatore (talk) 02:42, 15 May 2014 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

## Article Tone

This article often falls into the academic "we," which I don't believe is considered best practice on WP. If somebody wants to take the time and effort to clean that up, that'd be great. 129.237.189.235 (talk) 22:24, 8 May 2014 (UTC)

Yes, certainly. Are you that somebody? Then WP:SOFIXIT whenever they lift the semi-protection (or you get a real account). YohanN7 (talk) 23:04, 8 May 2014 (UTC)
I've removed the "we" language where possible and appropriate in most of the article. I've tagged the "Paradoxes" section with {{tone}}, since it might need some editing beyond simple removal of the "we" language; altering the wording to something that is less discussion-like might be beneficial and also take care of that issue. --Kinu t/c 17:29, 9 May 2014 (UTC)
I note that {{tone}} refers to Wikipedia:Writing better articles which states at WP:TONE: As with many such guidelines, however, there are exceptions: for instance, in professional mathematics writing, use of the first person plural ("we") as "inclusive we" is widespread. Deltahedron (talk) 09:05, 10 May 2014 (UTC)
It is widespread, even standard in mathematical writing. Whether our articles are mathematical writing, I don't know, but they are no textbooks by another WP:XYZ, and I personally think the "we" style doesn't sound encyclopedic, and it sounds very textbooky for sure. At any rate, mixing two styles in an article is a no-no. YohanN7 (talk) 10:36, 10 May 2014 (UTC)
I've found in my own writing that removing "we", while sometimes challenging, often leads to better prose. While it takes some effort, and while I feel no need to be dogmatic about "we"'s use, I do think it's best to avoid. Ozob (talk) 14:40, 10 May 2014 (UTC)
I rewrote Paradoxes completely. YohanN7 (talk) 10:53, 11 May 2014 (UTC)

## Setting of naive set theory (2)

I have made several changes. I have made Cantor's theory appear in a better light, backed up with sources fairly rigorously. Unfortunately, I managed to have, in the process, made Gottlob Frege look worse. I don't think he deserves that. Please help me think of better formulations. YohanN7 (talk) 16:13, 10 May 2014 (UTC)

Now Frege gets to share the dishonor with Peano and Dedekind. YohanN7 (talk) 10:56, 11 May 2014 (UTC)

Then there is our paradoxes article. It states (in the lead) "(Russel) ...and showed that naive set theory was flawed." Is this article on a flawed theory? Houston, we have a problem! YohanN7 (talk) 16:13, 10 May 2014 (UTC)

Among the problems we have is that the assertion at Paradox, that "Russell's paradox [...] showed that naive set theory was flawed." is, well, flawed. Firstly, the source cited appears to be an undergraduate dissertion which we would not normally regard as a reliable source: see WP:SCHOLARSHIP. Secondly the source states clearly that Russell found an inconsistency in Frege's axiomatic set theory. A later remark is "the (naïve) set theory of Frege leads to a contradiction". So the source, if reliable, only supports the claim that one particular naive set theory is flawed. The distinction between an axiomatic theory and a naive theory is not resolved. Deltahedron (talk) 11:09, 11 May 2014 (UTC)
I agree. Someone ought to edit the paradox article.
Another, rather curious, observation. The naive set theories observed to be paradoxical are, in fact, all, at least partly, axiomatic. How else can you show a paradox? Example: Cantors theory is naive. Cantors theory + unrestricted comprehension is paradoxical. I doesn't follow that Cantors theory is flawed, only incomplete. Then again, even ZFC is incomplete.
All set theories (naive and axiomatic) seem to be on footing. There is no sharp distinction, just varying degree of axiomatization.
An attempt to classify set theories would be into the decidedly inconsistent ones and the maybe consistent ones. The theories in the latter category are all more or less naive (or less or more axiomatic, if you prefer). YohanN7 (talk) 12:24, 11 May 2014 (UTC)
An aside: "How else can you show a paradox?" A "paradox" is not the same as "logically inconsistent argument". At its most general, a paradox is a conflict between expectation and observation (broadly interpreted), and the existence of an axiomatical treatment is not essential. Many paradoxes arise from situations in which intuitions are shown to be incompatible with theory or experiment. Monty Hall is a classic in this respect. — Preceding unsigned comment added by Paradoctor (talkcontribs) 13:27, 11 May 2014 (UTC)
Good point. This is another parallel of the inconsistent—naive—axiomatic terminological problem. But this one is simper. A "paradox" in this article the same as "logically inconsistent conclusions" (like 1 = 0) inferred by correct application of the "usual" laws of logic (or formalize this if you want). We just need to point it out. Many use "antinomies" istead of "paradoxes" here. But the named antinomies have all , well, "paradox" as a part of their name. YohanN7 (talk) 13:56, 11 May 2014 (UTC)
• It may help to quote Keith Devlin from the introduction to Fundamentals of Contemporary Set Theory:

Starting with the naive theory of Chapter I we begin by asking the question "What is a set?" Attempts to give a rigorous answer lead to the axioms of set theory

— Keith Devlin, Fundamentals of Contemporary Set Theory, 1979

## Let's move on....

OK, on rethinking it, even I don't support the proposed move to informal set theory. I thought it had possibilities at first, but with a little reflection, it doesn't really address the problem.

So can we close that and move on? Preferably before the semi-protection expires, so we don't have to deal with a certain noisy contributor? As unfortunate as the manner was in which it was brought up, there still is (at least one) problem.

The issue is that the term naive set theory is used in at least four ways:

1. To mean "all early set theory" (say, before Zermelo's work on formalization).
2. To mean Cantor's set theory specifically (this probably subdivides; Frápolli at least argues that there are at least two phases of Cantor's thought that should be distinguished).
3. To mean set theory that is vulnerable to the classical antinomies.
4. To mean "all set theory done in natural language".

I can identify two significant issues related to having an article called naive set theory, and they relate to different subsets of the above four. One is a POV problem; one is just more of a confusion.

The POV problem comes from conflating meaning number 3 (set theory vulnerable to the antinomies) with some or all of the others (especially with Cantor's theory).

The problem that's more of a confusion is brought into focus by reading many of the "oppose" !votes in the above discussion, where contributors say that naive set theory is the common name for "this". Most of them don't specify what "this" is, but seem to mean number 4, "all set theory done in natural language".

But for meaning number four, we might as well just redirect the title to set theory, because ALL set theory at the research level is done in natural language. Zero point zero zero zero percent of it is done in formal first-order logic. (That's for human mathematicians, of course; automated theorem provers may well work in formal first-order logic, but to my knowledge they are not yet producing new set theory at the research level.)

So what to do with the article? My suggestion — make it about the phrase "naive set theory", as I suggested somewhere in the archives. Then we can treat the four meanings without conflating them, and discuss the issues related to them, without implying that the phrase has a single well-specified referent. --Trovatore (talk) 01:08, 15 May 2014 (UTC)

What is the reader expecting? Is he expecting a classification of naive set theories into well-defined categories?
Some will come here to read about unions, power sets, etc, others come here to read about the classical paradoxes (yes, I know, antinomies, but paradox is part of their respective names anyway). Probably relatively few are interested in whether Cantor's version i or version ii were naive and/or whether they ought to be, or even are called naive. [From what I gather from the German Wikipedia (Google translated), Cantor, at least later on, did have some concept of a class in his arsenal. At least he had a name for them. Perhaps something for the article to mention.]
If we include "all set theory done in natural language", then we need Berry's paradox and similar paradoxes here. I think they should go in anyway to err on the side of inclusion rather than exclusion.
I think the present article does include all four of your items, although it isn't subdivided into and labeled according to them. Also, the article is pretty clear on were the classical antinomies come from (unrestricted comprehension), first early on (subsection Paradoxes) and the final section (Paradoxes again).
I'm not clear on what your suggestion means in full. It could be read as if we should throw out the current meat of the article (union, power set, etc) and keep (reorganize and rewrite) what is necessary to disambiguate the phrase "naive set theory". YohanN7 (talk) 18:25, 15 May 2014 (UTC)
It's not a subdivision. These are four things that have not much in common except for the name. Oh, of course 2 is a subset of 1, and 1 and 3 have some overlap, but the point is that the term "naive set theory" is, not just a "little" ambiguous, but has referents that do not naturally share an article at all, unless it's an article about the phrase. --Trovatore (talk) 19:51, 15 May 2014 (UTC)
If it is not a proposed subdivision (of the article), then I understand even less than I thought: Lead: ... The term naive set theory can meany any of the following: (list)... . Article body: A section each on the items in the list and probably one on paradoxes (as to not conflate). Nothing else. But apparently you have something else in mind. YohanN7 (talk) 20:27, 15 May 2014 (UTC)
Here's the point: The term has been used in various distinct ways, but not everyone agrees that all the ways are actually different. Some people, for example, take the view that Frege correctly formalized Cantor's theory, and that Cantor's theory was vulnerable to the Russell paradox; others do not. That's what needs to be discussed in the article. To some extent, it is discussed in the article. The real problem is not that it is not discussed; it's that the article is not worded in such a way as to make it clear up front that there is a discussion to be had.
Right, now I'm with you. There is the formulation "Some people believe that Cantor's theory wasn't ...". While we do let Cantor "defend himself" through the letter quotes later in that paragraph, it's not clear to the reader that there is disagreement here. I can't contribute anything here because I don't know much about the disagreement (except for its existence). YohanN7 (talk) 21:01, 15 May 2014 (UTC)
By the way, it occurred to me later that I had missed out a fifth meaning. I think some people use "naive set theory" to mean something more like "elementary set theory"; basically the Venn-diagram stuff. Basically where you have individuals, and you have sets, and you never really consider whether a set might be an individual itself and an element of another set. It could be formalized as a two-sorted theory, with one sort for urelements and another sort for sets of urelements, and there are no pure sets at all except for the empty set. That strikes me as a fine topic for an article by itself — but one that would have no reason to mention the paradoxes. Is that the meaning that most of the COMMONNAME !voters had in mind?? If so, that changes the discussion considerably. --Trovatore (talk) 20:42, 15 May 2014 (UTC)
This is what I think some readers will expect to find here. Sets with cats and dogs, intersections and unions…. YohanN7 (talk) 21:01, 15 May 2014 (UTC)
Yes, quite so. I think it might be worth having a standalone article on that topic. That article would have no need to mention the paradoxes except in passing. --Trovatore (talk) 21:05, 15 May 2014 (UTC)
Is that topic covered by Set (mathematics)? Paul August 14:08, 1 February 2016 (UTC)
Hmm, more or less, I think. Is it the "common name" referent for "naive set theory"? If not, what is? I still don't think it has been established what topic this article is, or should be, about. --Trovatore (talk) 07:52, 2 February 2016 (UTC)
Unfortunately, as you have pointed out above, the term "naive set theory" is ambiguous, and has been used to mean different things. Any article then, under this name, should discuss all those different meanings (though I suspect some will be difficult to source). And by the way I think that most people looking for an article on "naive set theory" will be sophisticated readers who will not be looking for the content in Set (mathematics) or say Set (mathematics). Paul August 11:29, 2 February 2016 (UTC)
Is there a reliable source for the usage (3), that "naive" means "inconsistent"? It may be a fact that all naive set theories are inconsistent, but so may non-naive theories. References, please. Deltahedron (talk) 20:08, 15 May 2014 (UTC)
OK, first I want to know what you mean by "naive set theory". You are one of the people who said, in your argument against the move (I'm not arguing that point; I also ultimately opposed the move), that naive set theory was the "term of art", without really saying what it's the term of art for. Can you please clarify what the topic actually is, in your opinion? If we can make that clear, then the article could maybe be saved, with perhaps a hatnote for other uses. --Trovatore (talk) 20:18, 15 May 2014 (UTC)
We go by what can be verified from independent reliable sources. I asked an entirely specific question about a statement you made, and I assume you had a reason for making it: if you know of sources that use meaning (3) on the list, please cite and quote them. I go by the usage of Halmos and Devlin which I cited and quoted above. Halmos used NST as the title of a book, of course, and it's pretty clear that he did not set out to write a book on the subject of inconsistent set theory. Deltahedron (talk) 20:30, 15 May 2014 (UTC)
Delta, please don't lawyer me. We're not fighting here. I'm just trying to understand what you mean by it. I don't have specific sources to hand, but the term "naive set theory" turns up all the time in a discussion of the paradoxes.
As for Halmos' usage, I haven't ever gotten around to reading his book, but his description of "naive set theory" is as far as I can tell indistinguishable from just plain "set theory" as actually practiced by researchers in the field. If I am wrong about that, can you please clarify what the distinction is? --Trovatore (talk) 20:45, 15 May 2014 (UTC)
I'm not fighting but it seems as if you are. I asked you (twice) to support statement (3) with sources and you refused to answer. My opinion is irrelevant. What counts is the usage of reliable sources that we can use to write the article. So once again, is there a source that equates the terms "naive" and "inconsistent", or is it just your personal opinion? Deltahedron (talk) 20:56, 15 May 2014 (UTC)
I do not know of any such source. I suspect they're out there. But to be clear, I am not equating "naive" and "inconsistent". I am just trying to figure out what the topic of the article is and/or should be. I believe that some people equate "naive", if not with "inconsistent", then at least with "includes unrestricted comprehension" or some such. If not, then well and good, we can leave that out of the article — but then we really don't need to mention the paradoxes at all, do we? --Trovatore (talk) 21:01, 15 May 2014 (UTC)
I think Hausdorff used the term as early as 1915, but I'm not sure. He the probably meant "vulnerable to classical antinomies" because that was pretty much all there was to chose from. You are not going to find it as a definition in any book, like in "a set theory is a naive set theory iff..." The concept is too murky for that. Halmos' book was mistitled anyway (according to himself as well) and does not define the term unambiguously. YohanN7 (talk) 20:48, 15 May 2014 (UTC)
Why was that "all there was to choose from"?? Cantor's theory as described in Jourdain's 1915 translation (Contributions) does not seem to be vulnerable to the classical antinomies. --Trovatore (talk) 20:55, 15 May 2014 (UTC)
"Pretty much all there was to chose from" because it was 1915, and I didn't say Cantor's theory is vulnerable to antinomies. I don't know if Hausdorff did either. But there were theories out there definitely vulnerable to these antinomies. What else could Hausdorff possibly have in mind when he wrote "naive"? YohanN7 (talk) 22:07, 15 May 2014 (UTC)
Again, what do the sources say? The history and development of set theory is complicated and is not something that can be settled by an informal ("naive"?) discussion here. Deltahedron (talk) 20:59, 15 May 2014 (UTC)
See above. --Trovatore (talk) 21:06, 15 May 2014 (UTC)
Felix Hausdorff: de:Grundzüge der Mengenlehre, Leipzig 1914, page 1f: "...naive conception of term set..." (My pathetic attempt to translate the German reference at Naive Mengenlehre.) YohanN7 (talk) 22:23, 15 May 2014 (UTC)
According to A history of set theory, the article of ours is fairly accurate with Cantor and the early paradoxes. But Cantor was initially critical of Burali-Forti's result:
It is believed that Cantor discovered this paradox himself in 1885 and wrote to Hilbert about it in 1886. This is slightly surprising since Cantor was highly critical of the Burali-Forti paper when it appeared.
There are a bunch of references for the linked web article (but unfortunately no inline citations). Perhaps something can be dug up from there. YohanN7 (talk) 00:07, 16 May 2014 (UTC)
I support Trovatore's suggestion. This would be the logically correct thing to do. The present article isn't very coherent anyway. (By the way, when reading my posts I realize that I sound..., well, almost rude in spots. This was not at all the intention. I blame it on my own linguistic confusion.) YohanN7 (talk) 08:45, 24 May 2014 (UTC)
Here is one more variant: ZFC but with urelements. Halmos allows for sets of kings and grapes (if I remember correctly). But, he also later on is clear to the point that all sets needed in mathematics can be built up from the empty set alone. I am, by the way, not clear on whether ZFC actually rules out urelements. There is just no way of constructing sets containing them (supported by ZFC). This isn't really the same as saying that they don't exist at all. YohanN7 (talk) 09:24, 24 May 2014 (UTC)

I came to this page hoping to learn something about set theory itself; I'm not interested in the history part. I went to the page on set theory but it was too advanced for me since I am a beginner in the subject. Is it ok if someone groups the actual math parts and the history parts into separate sections? Some sort of reorganization would be good. Jojojlj (talk) 23:26, 23 November 2014 (UTC)

Unfortunately, 'naive' in this context has a particular meaning to mathematicians that doesn't translate into "this is the article you want for the basics of set theory". For an article that covers the basics better, try Set (mathematics). Algebra of sets also has some good basics. We should probably have a hatnote for this. --Mark viking (talk) 00:56, 24 November 2014 (UTC)