User talk:Philogo

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Contents 1 Invite 2 Messages 3 Nav template 4 Banner 5 Argument (logic) 6 Atomic sentence 7 Deductive reasoning 8 Been thinking about you 9 interpretations 10 logic template 11 philosophy of logic main article 11.1 propositions 12 work on logic articles 13 Formal language (disambiguation) 14 Proposed deletion of Interpretation(disambiguation) 15 Philosophy/Quotations

[edit] Invite

I notice you signed up as an early proponent for the creation of WikiProject Logic. Since then, the proposed project has been moved to it's own space and you have been listed as a Charter Member. Thank you for paving the way for the creation of this project. This is an invitation for your continued and perhaps renewed participation and correspondence. Be well.

Gregbard 03:00, 14 July 2007 (UTC)

[edit] Messages

Leave any message that is not to do with any matter below --Philogo 00:49, 2 September 2007 (UTC)

Hi-- on the "Atomic sentence" page there was an error on the last example of the "Interpretations" section-- I think. I've corrected it, but since I've only been studying logic (propositional calculus) for about a week I figured it was best to direct your attention to it as well, in case I've totally messed up. Thanks for your contributions, by the way, they've really helped me review some of the material I'm covering. -DWRZ (talk) 15:40, 9 December 2007 (UTC) Hi - I see you picked up on missing closing parenthesis and spelling typos. Thank you. The examples are of first order predicate calculus, and since you have just started proposional calculus your are obviously reading ahead! Let me know if you have any suggestions for further articles. My idea is that logic articles should be comprehensible to people who do not already know the answer.

Thanks and good to hear. I've actually found the articles quite helpful and in many cases much clearer than the textbook. The fact that there are few other well organized online resources makes this a much more critical resource IMHO. I'm winding up my exam season now, but after that I do plan on looking around the articles a bit and helping out in minor fixes and feedback (student perspective).

One thing which does have me stumped at the moment is that I can't find the equivalent English (word or maybe the article doesn't exist) for what the Italians call "alberi semantici" (I'm currently enrolled in my semester abroad in Italy). The literal English would be "semantic trees", I think... it is used as a way (indirect method) to check if a proposition/wff (it works with both propositional and predicate calculus) is a tautology or not by starting with the assumption that the proposition/wff is false. Structured like a tree with the original proposition/wff as the "radice" (root) and the atoms as "foglie" (leafs). Sorry if the description makes no sense-- I've only got a basic grasp of the concept at the moment. Anyway, does this ring a bell as to what it might be in English? And if so, is there an article for it (if not, I'd be willing to start some work on it once break begins).

Again, thanks. ----DWRZ (talk) 16:52, 18 December 2007 (UTC)
They are called "truth trees". There seems to be no Wiki articel on it but I find soemthing at this address, but not read it:-

http://www.earlham.edu/~peters/courses/log/treeprop.htm

A sentence can be shown to be valid by putting its negation in the root, and then you find all branches are closed, i.e. the negation can never be true. Consequently the senttence itself must be logically true (a tautology if in sentencial calculus).
You can also test an argument for validity like this. In the root put the premises and the negation of the concusion. If the argument is valid then all branches are closed (i.e there is no interpreation with true premises and a false conclusion.) Interestingly there are some sentences which if you put them in the root, you can never draw the whole tree in finite time (there are always some more branches) so you can never tell - in finite time - if the tree is/would be closed or not. See if you can find one and say what you can conclude about such sentences. --Philogo (talk) 14:00, 16 January 2008 (UTC)

Thanks. This is exactly what I learned, but I was not sure what the name was in English. I'm not really sure about the question-- it sounds interesting and I remember talking about computability issues in my AI class. I don't think I'm quite at a level to answer this yet, though. :\ In any case, to answer your other question-- I finished my logic class last semester, this semester I've still been doing philosophy (which is my major) but nothing logic related (and it's been a very tough semester otherwise). Next September I'll be back in the States and it's very likely I'll be back in Logic then. In the meantime I'm in my exam period-- afterwards I'll be away from the net for quite some time, so I may not be able to contribute much again until July. If there's anything I can help with now or in the future though, let me know, it would be great to help out. Again, thanks for all your work and help. --DWRZ (talk) 18:59, 14 May 2008 (UTC)

Nice to hear from you again --DWRZ. I will leave a sentence here for infinite tree sometime. You contributions and commente always welcome. I am trying drum up interest in the negelected philosophy of logic article just now. Keep me posted on your adventures in Philoland.--Philogo 20:58, 14 May 2008 (UTC)

[edit] Nav template

I didn't find a good way to transclude the lists, so there are two of them. One is at Template:logic, and the other is Portal:Logic/Logic topics. However, if you click on the tiny little "e" in the upper left corner of the template, that will let you edit it. For more parameters of the template, check out Template:Navbox generic. Hope hope this helps. Gregbard 22:09, 20 August 2007 (UTC)

I deleted the one and transcluded the other on the portal.Gregbard 10:34, 21 August 2007 (UTC)

[edit] Banner

If you click on the tiny little "show" on the philosophy template, it unfolds to show a link to the logic project. The philosophy banner has options for all various branches of philosophy (more than one if needed). After the big round of compliants entirely form math people, I decided to get things ready for a segregated project. We will end up with the math people responsible for "their" categories, with a work list of their own (under Project Math/foundations), and the "philosophy" people will have "our" categories. Do you see how there is two of everything at WPLogic, well its more of the same. I could use a little input on the proposal I made at WPPhil.

Gregbard 23:27, 30 August 2007 (UTC)

Erm, have I turned over a stone? By "segregated project" do you mean there will be two Wikiprojects Logic, one fr amths people and one for philsophy? or perhaps soem articles therin tobe maintained by maths people and one by philospohy people? I am somewhat confused.--Philogo 11:56, 31 August 2007 (UTC)

I'm not sure how it will work out. The math people can hold whatever they want hostage. I think there will be a list of categories for the math people, and a list for the philosophy people. There will be two links at WP:Logic one to the philosophy logic assessment worklist, and one to the math foundations worklist. Together the two lists will be the whole of it. As new articles come in we will put them in one or the other. They get the math tag, we get the phil tag with no logic tag per se. There will probably be orphan articles neither want to claim. There will be some we both insist on including. (a good claim for keeping the logic tag I guess) The goal will be to make the overlap small I guess. They don't want anything to do with that fuzzy philosophy stuff. This way we are limited to just two banners and not potentially three.

My whole point in my latest effort is getting ready for automatic bot tagging. I would like as few complaints as possible, so segregated is probably the way to go. They can be responsible for their stuff. They have a "foundations" section for it. The best we on the philosophy side is to hold them to it. I.e, ask them to tag any articles in those categories with math foundations and be responsible for them.

I'm open other ideas. Please take a look at some of the task force categories I have laid out at WP:Phil. These are just supposed to be the ones whose every article gets tagged philosophy, and as a part of the particular task force. Then check out the break down.

Be well,Gregbard 12:30, 31 August 2007 (UTC)

I have turned over a stone! Are you saying that it is proposed that: a) There is a WP Logic b) WP Logic will have two task lists one (A) will be on the philosophy logic assessment worklist and the other (B) on the the math foundations worklist. c) Articles on the (A) list will get the phil tag those on the (B) list will get the math tag. There will be no logic tag so no article can get it. d) By "logic tag" do you mean a banner that says "this article is within the scope of WP logic" (i.e like {{logic3}}? --Philogo 12:47, 31 August 2007 (UTC)

The goal is to cut down on tags since everyone hates them. I think they are wonderful tools for collecting data. I don't know if there will end up being just a plain old "logic tag" unless it is for A) articles which both projects reject or neglect as their own, B) articles both claim as their own but will only have the one tag (I don't think the math people will go for this) or a strange project consisting of both A) and B).

The creation of the multiple "task forces" at WP:Phil is not so much an attempt at user space for a group of dedicated people to a task, as it is a tool for categorizing. The task force language kind of came with the format. It doesn't matter if anyone ever signs up really. It's about the tools.

Altogether it is designed to catch everything in philosophy in at least one category.Gregbard 14:00, 31 August 2007 (UTC)

Gregbard 14:00, 31 August 2007 (UTC)

If a “tag” is like {{logic2}} or {{logic3}} what's to hate? We are just editing /writing article for an encyclopaedia are we not - what's wrong with such a tag on a talk page? Puzzling.

Where can I read what these "Maths people" are saying? A lot of people, including myself, are interested in Logic & they may have different academic backgrounds. I can see that various Logic articles might be of interest to Mathematicians and Philosophers and maybe some such articles are more interesting to the former or the latter. However if we are to have a WP Logic then I feel that Logic articles should be tagged as under the WP Logic remit. (I do not see any reason why they should not also be tagged under WP Logic and WP Maths as well, although I cannot see this as having a tremendous advantage. ) However, although I have not read all the arguments you refer to, I feel that if WP Logic is to prosper, so that the standard of Logic articles improves (they are very mixed I feel) then they should not be tagged MATHS or PHILOSOPHY instead of Logic; in other words “as well” OK, “instead”, ¬OK. Logic I feel should stand on its own and not just as a branch of Philosophy or a branch or Maths. I certainly do not think that some Logic articles should be treated as Philosophy-Logic and others Math-Logic.; I feel that such a distinction is spurious and the demarcation would be impossible. (There is in my view a distinct subject, Philosophy of Logic, as distinct from logic as Philosophy of Science is from Science. THIS should certainly come under WP Philosophy, and the page of Philosophy of logic is woefully neglected, to the shame of WP philosophy.) For logic articles I hold out for a Logic tag like {{logic3}}
--Philogo 18:48, 31 August 2007 (UTC)

[edit] Argument (logic)

I'm not sure if you're aware of this, but there's also logical argument, which at first glance from a non-philosopher like me seems to be about the same thing.

Actually, you've been editing that one too, so you must know. Surely the names should be changed then at least.

Ah, by the way, please avoid using capital letters improperly. For example, logic should not normally be capitalized as you did here [1]. The same goes for article titles and headings within articles. Cheers. Richard001 (talk) 05:23, 26 January 2008 (UTC)

Hi Richard001. You are quite right the articles are supposedly on the same subject. I edited Logical Argument a bit but decided that it was so poor that I would start over and Argument(Logic)is the result. I am not sure what your interests are but if you were interested in what the term Argument meant in Logic (and presumably you were new to Logic or would not be looking it up) which do you think would be the more helpful? Logic as a subject values clarity and precision very highly (you should read the scoldings Frege gives his fellow mathematicans, and sets the tone for the precision requried in Logic. It is therefore just a little tricky to be precise in this way and yet readable to the novice; precision and readabilty, and no waffle is what I am aiming at. I imagine that in some Darwinian way one or other of these articles will be deleted or be "merged" into the worst of both worlds.

I took the opportunity to use what I consider a much better title (Argument (Logic) for the following reasons. Often a word which has a meaning in common speech has a special meaning in a particular discipline. Take 'Force' for example. We might have articles explaining its use in different subjects like this: Force (Physics) : Mass x Acceleration; Force (Law): Physical means of obtaining compliance. {I have just made the definitions up). The word "Argument" has a particular and precise meaning in Logic. It is not the same the argument of a function, not is it a heated dispute. Nor for that matter is it an attempt to persuade, and it is akin to but not the same as the arguments that a lawyer or philospher might put forward in support or refutation of a particualr point of view. 'Tautology' also has a special meaning in Logic - not the same as in Literature. ( I beleoive the term was first used in Logic and given its defeintition by Wittgenstin. Therefore we would be best off with articles with headings like Force (Physics); Force (Law); Argument (Logic); Argument (to a function or predicate); Tautology (Logic); Tautology (Litt.) Anyway "Logical Argument" is just silly. A fallacy is an argument in Logic but it is not valid. Does 'Logical Argument' denote just valid arguments (an exclude fallacies); or does it mean Argument as used in Logic? If the latter the its like saying 'Physical Force' for 'Force (in Physics) and 'Functional Argument' for Argument (of a function), or 'Musical Note' to mean 'Note (in Music).

Mea culpa re capilisation. I would say Logic the subject like Physics the subject should be capitalised - I can see the logic (not Logic) in that.--Philogo (talk) 01:20, 9 February 2008 (UTC)

I don't think it's a good idea to just start a new article on the same thing if you don't like the present one. For one thing, the editors of the present one are likely not to even notice that there is a new article on the same subject. In any case, we never have two articles on the exact same subject, so they'll have to be merged. Richard001 (talk) 05:06, 13 February 2008 (UTC)

On refelction the two articels are NOT on the same subject; Argument(Logic) is about arguments in just Deductive Logic; logical argument is of wider scope & not so resticted.--Philogo (talk) 14:27, 18 February 2008 (UTC)

[edit] Atomic sentence

If you have a minute, could you discuss on Talk:atomic sentence the technical mistake I pointed out with the sentence you added to the lede of that article? — Carl (CBM · talk) 14:20, 20 February 2008 (UTC)

• I think you editeed mid my edit. As I left it just now there is an opening defection, then two sentes which follwo from it concerning sentential and predicate logic. I have suggestd that we discuss future edits on top of use page before making them. Also I invite you to join me re para on atomic sentences in natural language. OK--Philogo (talk) 14:51, 20 February 2008 (UTC)

[edit] Deductive reasoning

In Wikipedia articles, we do not speculate about an author's intent. We do not insert quotes without external sources (meaning outside Wikipedia). The wording of the sentence about the Sherlock Holmes story was the result of much negotiation to find neutral wording which only says that they referred to it without indicating whether they were right or wrong. I can throw a dozen definitions at you which say that the term was correct in many cases, but there's no need to do that. All the article needs to say is that it's a cultural reference, which is correct. It is indeed a reference. The article does not say Holmes used deduction.Wryspy (talk) 04:24, 11 March 2008 (UTC)

By the way, you are correct in guessing that someone messed with the sentence about Newton's reasoning. It originally said that Newton induced the theory of gravity and used that to deduce specific conclusions. Wryspy (talk) 04:30, 11 March 2008 (UTC)

Wryspy: Please give your reasons for your edits on the talk page for the article, so that others can see the reasons for your edit. Thanks. --Philogo (talk) 13:44, 14 March 2008 (UTC)

1. In case you didn't notice, that reason was a bit lengthy to cram into an edit summary. 2. You stated that you reverted because I gave no reason in the edit summary. Yes, I did. It says, "Do not speculate." -- which still holds true. Don't speculate about the author's intent. 3. If you want someone to see your comment to them (above), you need to post it on their own talk page. If I hadn't felt like coming here right now to respond to the remark you made in your edit summary, I would have never discovered this. I have no reason to watch your talk page. Wryspy (talk) 17:13, 16 March 2008 (UTC)

[edit] Been thinking about you

I want you to know that when I set up the logic project with the two worklists against your protests, it wasn't done lightly. I didn't know what to do about all of the conflicting positions, so I did the best I could. Pretty much ever since then when I see your username I think about the fact that you are still probably unhappy with me about it. I can't really blame you on that issue since I basically took the initiative and pursued what I saw as the best compromise. I think about it from time to time and I still don't know what other way to do it that wouldn't piss someone else off. In any case I think it is working out all right as separate lists so far.

Anyway, thanks for your work on interpretation. I think we are pretty much on the same page there for the most part. Be well, Pontiff Greg Bard (talk) 10:47, 5 May 2008 (UTC)

Gregbard, nice to hear from you on my talk page, which has few visitors. At the time of the our split-no-split "debate" I was puzzle by your references to wars and maths people &c. I have a little more idea now, and I understand why you supported the split, but I foresaw the consequences. The big split. We will finaish up with precise but to non-mathemacticans incomprehensible defeintions from matn peiple for MAths logoc, and imprecise and fluffy articles under Philosphy MAths. I say Logoc is Logic. Philopsy of Loogc is not a type of Logoc any more than Philosophy of Science as a type of science. Ae have precatiocally zero articles on Philosophy of Logc issues, adn we are not gong to get them until we have a set of comprehensible AND preocise areticles on the (relatively straight forward) basics of Elementry Logic. Now there seems to be some idea (among the maths people anyway) that there is one thing call Mathematical Logic and in a parallel universe another thing called "Philosophical Logic" which has alternative definitions of all the terms like validity and interpretation. They have got this in their head now and it is taking a lot of time to disabuse them. And I think that the source of this confusion is the split that I opposed. You will see that in the article on interpratation (which you kind of invited me into) I said right at the beginnng that I was unaware of their being more than one definition nad I think, many hours late, this is being somewhat half-heartedly acknowledged. The math people (god bless their socks) are really reluctant to let go the idea that there are two meanings, despite all indications to the contrary. To my mind people with Science and Math backgrouns find it more diffcualt to expalain ideas to people from other backgrounds than people with Arts backgounds, e.g historians. They assume that the terms they are familiar with are familiar to all (cannot think why it is obvious that they are not, and they msut sulrly remeber all teh works they put it for they themsleves to learn them). Also I supect that they use a term like "wrong" sometimes to mean incorrect and sometimes inadvisable. Not all scientists and "math people" I hazard to add. I can read Frege an Russell with ease for example, since they write both precisley and clearly and define all their terms. Please look at my very last posting to Interpretation where I make a heart-felt plea that we should write both precisley and comprensibly to the intended audience, the intelligent non-specialist. I suspect that of we all co-operate and not be rude then we might finish with readable article of which we can all be poroud and happy. Then we can jointly tackle another one.

PS I still say, if I might be so bold, that you are wrong to say that in an interpretion you must "name" every object, and I suspect you are misremembering the requirement to assign an object to every individual constant. As you say, be well--Philogo (talk) 12:21, 5 May 2008 (UTC)

If I can comment as a mathematical logician, it isn't true that we think there are two definitions of validity, one in mathematical logic and one in philosophical logic. One way of looking at things can be very roughly sketched as: logic done using the tools of mathematics is mathematical logic, while logic done using natural-language tools is philosophical logic. Of course there isn't a sharp divide, since many philosophy papers have a mathematical component, and many mathematical papers have a philosophical component (at least in mathematical logic). Another distinction is in the area of focus: philosophical logic is more likely to be concerned with philosophical issues, mathematical logic more interested in technical issues. The field of "logic" of course includes both sides, which are inseparable.

A confusing issue for me is that in many cases there is already an article on the mathematical definition; so if that is the only definition in all of logic, it would be easier to redirect all the pages to the same place rather than duplicating the material. The only reason I can see to have a page named interpretation (logic) is to talk about interpretations other than first-order structures, because we already have an article on first-order structures (although it could use a some polishing). In short: what material should go into interpretation (logic) that isn't already covered elsewhere? It's natural to suspect that such material exists when editors start to expand an article rather than redirecting it.

This issue appears again in atomic sentence. In the context of first-order logic, there is no interest in atomic sentences; it's just the intersection of two definitions, and there isn't really much to say. In this case, I know that there is more to say in the context of natural-language sentences and the theory of truth. That is what should go in the article on atomic sentences. I think that a possible reason for the slant toward mathematical logic in some articles is that nobody who knows that philosophy side is adding that material to articles, which only leaves the mathematical portion of the material visible.

A parallel situation would be if lots of physical chemists were on Wikipedia but few organic chemists. The basic articles would seem to be biased, but that's only because one major area had not been filled in, not because the physical chemists were actively trying to suppress organic chemistry. — Carl (CBM · talk) 12:59, 5 May 2008 (UTC)

Hello visitors, one and all. I disagree with "logic done using the tools of mathematics is mathematical logic, while logic done using natural-language tools is philosophical logic.". Logic as studied by and of interest to philosophers is largely the same as mathematical logic (formerly symbolic logic). Philosophical Logic is not Logic as studied by philosophers. Philosphical Logic is philosophy, logic informed enquiring into questions about the nature of language and thought and contents and structure of the world, not Logic. (See Grayling, An introduction to Philosophical Logic, 1982.): The Philosophy of Logic is the study of issues arising FROM Logic. (see work by Quine for an example) Similarly the Philosophy of Science is NOT an alternative form of Science, and Philosophy of Maths is NOT as alternative form of maths. There are respectively the study of (philosophical issues) that arise FROM science and maths respectively. However I suspect that the following may lead to the confusion. When mathematicians study Logic they are perhaps mainly interested in its applications in Mathematics (just as computer scientists are mainly interested in its application in computer science. Philosophers however are interested in the application of Logic in ALL universe of discourse. Indeed they would argue that if e.g. a sentence were not valid in ALL interpretations, e.g. with three philosophers or even three flying horses, with all universes of discourses, then it would not be logically valid. That is perhaps why when philosophers give examples of interpretations with they often come up with such intentionally odd examples, round square copulas and women who have landed on the moon. They are not intended to be "informal" interpretations, simply possible interpretations, on the grounds that that it exceptions that prove (i.e. test) the rule. Another reason why philosophers might suggest "All men are mortal" etc for their examples are this. For the non-specialist, says an archaeological student, or a philosopher mainly interested in Epistemology, Ethics or Philosophy of Science he or she can more easily follow and understand and discuss such such an example with another person than an example involving mathematical objects with which he or she may be unfamiliar. Therefore my hope is that WikiProejct – Logic results in Wiki (logic) articles that are precise and comprehsnsible to the non-specilist and all those who are willing and able to contribute, be they mathematical logicans or not, do so.

I don't follow what you are saying about interpretations. An interpretation in first-order logic is precisely a structure, they are synonymous up to trivial translations like identifying propositional variables with nullary relation symbols. Do you agree with that statement?

Sorry that you did not follow what I am saying about interpretatians; sorry but I do not follow what you are saying in your last enetence. (I would have to read structure first.--Philogo (talk) 21:02, 5 May 2008 (UTC)

If you can get a copy of the book, I recommend reading the introduction to Donald Monk's Mathematical logic to get a better exposition of the way some mathematical logicians view the relationship between mathematics and logic. I quoted parts of it here. My explanation above isn't very good, I know. — Carl (CBM · talk) 14:18, 5 May 2008 (UTC)

Yes I'll do that but I'm a bit busy reading Frege just now.

When I was invited to join Wiki-Project (Logic) and I was quite keen because I thought there were some really pretty bad articles (as well as some good ones). The bad ones, so it seemed to me divided in two types. (a) Those that were hopelessly muddled and woolly (b) those that tried to explain basic concepts using terms that would be less familiar to the ordinary reader than the term or concept being explained. Then there came the proposal that Logic articles should be edited not by one team, but two. Some logic articles would be deemed mathematical and some philosophical. I very much opposed that and I foresaw the subsequent developments. I also noted that there practically zero articles on Philosophy of Logic to Wiki-shame. I now fear that there will be none because the term "Philosophy of Logic" and "Philosophical Logic" appear to be now reserved for those articles that mathematical logicians would not touch with a barge pole. I short I am a rather disillusioned Wiki-Project (Logic) founder member, and apparently in good company (scine everybody else seems to have pretty much bizzed off months ago). I am also rather put off by the insults flying about and general posturing which is not conducive quiet rreasoning to article-improvement. I could not BELIEVE the length of the discussion pages on Interpretation (Logic) at which I was invited to look at. So many words! So many insults! So little progress! There seems to be no reaction if I flag an article as in need or improvement and no volunteers to form a team to work on the article. Consequently my articles and edits are sporadic at best. I suppose I feel my time is better spent reading, Frege for example. As I said above my hope is that WikiProejct – Logic results in Wiki (logic) articles that are both precise and comprehensible to the non-specialist and all those who are willing and able to contribute, be they mathematical logicians or not. I would not think this wee a forlone hope, and would be less discouraged if anyone expressed their agreement with that hope.--Philogo (talk) 21:02, 5 May 2008 (UTC)--Philogo (talk) 21:02, 5 May 2008 (UTC)

I am also interested in articles that are both precise and accessible, and I am confident that many of the other "math editors" are as well. So you are far from alone there.

Personally, I think that it's better to improve existing articles, rather than have multiple articles on the same subject. Wikipedia is full of these suplications, where people in different areas create articles separately about the same topic.

For example, the object that assigns semantic meanings to a first-order language is called a structure in mathematical logic, as well as an interpretation, depending on what field the author is in. One article on it is at structure (mathematical logic), although it could use some editing for accessibility and completeness. Unfortunately, I think Gregbard didn't realize that, so he created a second article at interpretation (logic). More unfortunately, he made a few technical mistakes when he created it, which math-centric people often focus on to the exclusion of the broader issue.

My preferred solution, if the article on "interpretation (logic)" is really just meant to talk about first-order structures, is to redirect it to the established article and improve just that one article. — Carl (CBM · talk) 22:44, 5 May 2008 (UTC)

I understand the term "signature" is similar in meaning, but how do the terms differ how are they helpful? I understand the idea of one topic one article but I think that structure (mathematical logic) for example is FAR too complicated for our intended readership of (Logic) articles, and I doubt that it could be made comprehensible to them by editing and therefore I can see why Gregbar might have started a new article. We need a set of Logic articles that are clear and precise suitable for people who are not mathematicians. (That achieved those of us who are interested in such things could begin writing some surely need Philosophy of Logic articles.) To achieve it however I think we need the collaboration and assistance of mathematical logicians. I disagreed with Gregbard in agreeing to designate some articles to be maintained by "maths people" and some by "philosophy people" and none by both or Logicians. This prevents collaboration on the articles for people who are not mathematicians. I thought it would lead to the death of Wake-Logic and I think it just about has. We could however change our minds and agree to collaborate again. e suld agree that some articles can and should be maintnaed by all WikiLogic people. By the way, ref interpretations, LTF Gamut in Logic Language and Meaning Vol 1 Introduction to Logic Chap 3 points out that the provision of interpretations of e.g. a unary predicate letter A by associating it with the extension of a set is not the only possible way of providing an interpretation. We might also interpret A as a property and determine whether a given element of D has this property. Indeed this seems to be the most natural interpretation. What we have done here is to take, not properties themselves, but the sets of all things having them, as the interpretation of unary predicate letters. The exploration of these two approaches would be of some interest and might make an interesting Wiki-Logic article. The usual extensional approach has the following drawback. Consider two distinct properties having the same extension, and assign those extensions to two predicate letters, say A and B. Since the extensions are the same the "meanings" given to A and B are the same in the interpretations. (In older temrs "meanings" are associted with denotations rather than connotations) The distinctiveness of the properties is not reflected in the interpretation. Thus under this theory of meaning to say that I am Walter Scott means the same as saying I am the author of Waverly. If we avoided this by using intentional rather than extensional interpretations, what would be the ramifications in Mathematical Logic? --Philogo (talk) 01:02, 6 May 2008 (UTC)

It can't see that it makes much difference for first-order logic, because there are no variables that range over predicates or relations. So there is no equality relation between relations themselves, and the only way to say two relations are the same is with a formula like .

But it is a known issue in higher-order logic. In that context, it's necessary to add extra extensionality axioms if they are desired. Otherwise, it is perfectly possible for two higher-type objects to be extensionally equivalent but not equal.

The downside of extensional equality shows up in higher-order arithmetic. Extensional equality of higher-type objects (even type 1) isn't decidable, and thus can't be included as a basic relation in intuitionistic systems or very weak fragments of arithmetic. But if the axioms of extensionality are dropped, and intensional equality is used, then it is possible to include a decidable equality relation for higher-type objects. I think that's the system Goedel used for his work with intuitionistic arithmetic.

By the way, I completely agree that the article structure (mathematical logic) isn't as accessible as it can be - but I think the solution to that is to improve it rather than duplicate the same material elsewhere. — Carl (CBM · talk) 11:08, 6 May 2008 (UTC)

[edit] interpretations

Carl: Would you be willing and able to set out the reason why the domain of an intepretation must not be the the empty set?
Do you agree that there is no such requirement with regard to the intepretation of predicates?
Do you agree that it is the denotation of some set s, not the set s itself, that is assigned to some predicate Δ in an assignment?
--Philogo 09:49, 10 May 2008 (UTC)
We have accepted a definition of interpretation that requires that (among other things) it assigns with each n-ary predicate of L or of Φ an n-ary relation among elements of D. Would you agree that the nature of this assignment is such that:
If Ά is some assignment and Δ is the domain it has declared and Φ is some one-place predicate and Θ a sub-set of Δ defined as being those elements of Δ that have some property Ρ and Θ is assigned to the denotation of Φ and ά is some individual constant that is assigned to some element ε of Δ, then the sentence Φ(ά) is true under Ά just in case ε is an element of Θ and ε has the property Ρ?
--Philogo 10:16, 10 May 2008 (UTC)<br /

see and compare Property (philosophy), lede, para 4, which says:

In mathematical terminology, a property p defined for all elements of a set X is usually defined as a function p: X → {true, false}, that is true whenever the property holds; or equivalently, as the subset of X for which p holds; i.e. the set {x| p(x) = true}; p is its indicator function. It may be objected (see above) that this defines merely the extension of a property, and says nothing about what causes the property to hold for exactly those values.

--Philogo 11:35, 10 May 2008 (UTC)--Philogo 11:39, 10 May 2008 (UTC)

An important reason for not allowing the domain of discourse to be empty is so that equivalences like:

,

where x is not free in φ, are logically valid. This equivalence is not logically valid when empty structures are permitted (e.g. let φ be and ψ be x = x). So the proof theory of first-order logic becomes much more complicate when empty structures are permitted, but the gain in allowing them is negligible, as both the intended interpretations and the interesting interpretations of the theories people study have nonempty domains.

For the other question, it seems to me that you are defining Θ twice: it cannot both be defined using property Φ and predicate P unless these are identical. So I don't understand what you are asking. — Carl (CBM · talk) 21:16, 10 May 2008 (UTC)

Thanks Carl, I will ponder para 1 when less tired. I was curious myself, and others are, and I thought that it might make an interesting section to our article

re para 2, I got my greek letter twisted. I was using greek letters to make clear they are meat-symbols. I'll tr again, and then I hope you will see what I am asking.

I should have written:-

If Ά is some assignment and Δ is the domain it has declared and Φ is some one-place predicate and Θ a sub-set of Δ defined as being those elements of Δ that have some property Ρ and to Φ is assigned the denotation d of Θ and ά is some individual constant that is assigned to some element ε of Δ, then the sentence Φ(ά) is true under Ά just in case ε is an element of Θ and ε has the property Ρ.

Is that correct?

Just in case I have screwed it up again:

Given:

Ά: Some interpretation

Δ: The domain

Φ: A predicate (symbol)

Θ: A subset of Δ

d: The denotation of Θ

P: The property that defines the set Θ

ά: some individual constant

ε: Some element of Δ

If the interpretaion associates the predicate (symbol) Φ with the denotation d, and the individaul constant ά with the element ε

then the sentence Φ(ά) is true just in case the element ε has the property P.

Eg if the predicate letter F is associated with the denotation d of the set s of white things (defined as having the property (is) white) and b is associated with a particular thing say my pen, then under this interpreation Fb is true just in case my pen is a member of s the set of white things i.e if my pen has the property of whiteness/is white.

--Philogo 22:23, 10 May 2008 (UTC)

Yes, if the domain D is some set of pens, F is the set of elements of D that are white, and c is some constant symbol interpreted as a particular pen, then Fc will hold in the structure if and only if the pen represented by c is white. This seems to me a matter of definition, so I think I may not understand what you're asking.

By the way, it's certainly true that the interpretation of a unary relation could be the empty set, even in the convention that the domain cannot be empty. — Carl (CBM · talk) 00:52, 11 May 2008 (UTC)

And even not only of a unary one. --Cokaban (talk) 11:00, 11 May 2008 (UTC)

I just chose a unary one to simpify the discussion. I understand (I hope) now why the allowing the empty set as the domain would complicate proof theory. Why does the same problem not arise if do not require predicates to be associated with non-empty sets?--Philogo 11:47, 11 May 2008 (UTC)

Bear with me, I can explain that very clearly. As I said above, the difficulty with empty domains is certain inference rules that permit quantifiers to be passed across logical connectives. For concreteness, look at

This is satisfied by an empty domain. To put this in prenex normal form, we want to move the existential quantifier to obtain

But this new formula is not satisfied by an empty domain, as there is no element with which the existential quantifier can be instantiated. The underlying issue is that the scope of the existential quantifier has changed to include the left disjunct.

The reason that empty (that is, identically false) relations don't cause this problem is that there is no similar notion of passing a relation symbol across a logical connective, enlarging its scope in the process.— Carl (CBM · talk) 12:18, 11 May 2008 (UTC)

I will poder this carelfully when next on-line. Meanile I have posted you admirable explantion to our article pro tem under notes. where all may read--Philogo 13:12, 11 May 2008 (UTC)

This made me think about something for the first time. In set theory, there is a generalized quantifier

which states that there is an element x in the set A that satisfies formula φ. The equivalence

requires both that x is not free in ψ and that A is nonempty. The issue I discussed above is a reflection of the same behavior. — Carl (CBM · talk) 12:25, 11 May 2008 (UTC)

I am glad you are getting something out of this discussion

Philogo, the problem with the empty domain is not really a problem, it is more like an inconvenience of having always to consider this case separately, because the reasoning of the sort "let x be an arbitrary element of the domain..." will no longer work. There are no problems in general with having "properties" not satisfied by any elements of the domain. (Sorry if my comment is not to the point, i have not read all of the discussion. Feel free to remove it.) --Cokaban (talk) 13:01, 11 May 2008 (UTC)

It is to the point. Other have asked "why is there this requirement" (non-empty domain.) I have anticapited the further query "Wny is it allowed for properties" . I good answers to put in the articele, where they now are under notes.--Philogo 13:12, 11 May 2008 (UTC)

[edit] logic template

Main article: Template_talk:Logic#Philosophy_of_logic

Call it a hunch, but I think you may have an opinion on the discussion about what to put it the section on philosophy of logic. Pontiff Greg Bard (talk) 01:32, 7 May 2008 (UTC)

Save yourself a lot of pain. Please just kindly post your reasoning on why the recent addition to the logic template of "logical positivism", by Greg Bard, with no citations and no definitions should stand. Jok2000 (talk) 20:35, 8 May 2008 (UTC)

Oh hullo Gregbard and Jok2000. Am I invited into another dispute? Well Gregbard, your intuitions have certainally picked up on something, but not QUITE spot on. I was not about to make a comment on the logic template but having become a little weary of editing (logic) articles I was about to have a look at Philosphy of Logic articel whcih looks quite forlarn. If either of you join me there, please be presere civility and rationality, and do not revert without giving a reason first in the discussion page. Peace ---- and Reason--Philogo 23:27, 8 May 2008 (UTC)

PS Jok2000, you ask me to post my reasoning on why the recent addition should stand. Are you not assuming that I think that they should stand?--Philogo 09:04, 10 May 2008 (UTC)

[edit] philosophy of logic main article

Good day. I am interested in helping out at the Philosophy of Logic. I would probably want to have a book to cite from, but would want to buy a book that you would accept citations from. Searching on amazon has been slow. Is there one you would like me to use? Jok2000 (talk) 02:22, 13 May 2008 (UTC)

Hello Jok2000 (talk). My suggestion would be that you choose a topic about which you would be interested or have some knowledge and work on that. That might involve looking at one or possible more texts. Depending on your knowledge and motivation etc. you might work alone or in collaboration, either by writinng an article or helping edit it for readabilty, checking citations, demanding explantions & so on. If this makes sense, IS there a topic that appeals and in what role(s) would you feel most comfortable? Depending on what you say I can suggest some texts. --Philogo 12:53, 13 May 2008 (UTC)

see Talk:Philosophy of logic

[edit] propositions

Hi Rick.Rick Norwood Re your recent postings re propositions and statements Untangling and clarification of these and similar terms falls within the province of philosophy of logic rather than Logic. It would be better to discuss then set out these issues in the nascent article philosophy of logic discussion at Talk:Philosophy of logic#Truth, Propositions and Meaning. If you owuld be intersted in this topic join me there.--Philogo 21:40, 27 May 2008 (UTC)

[edit] work on logic articles

I notice that we are both working on logic articles. I don't want to duplicate effort. Since you seem to be coordinating this work, if you would like to assign me an article, I'll be glad to work on it. Rick Norwood (talk) 12:47, 14 May 2008 (UTC)

Hi Rick. I had not so much thought of myself as co-ordinating as being last man left standing in poor WikiProject Logic. I imagine you are looking at the Wikiproejct task list pages in need of attention. I have been adding to the list from time to time in hopes of attracting some attention. If you look I have annotated lines "edit in pregress" when true. I suggest we use that list as our things-to-do. I know I have shadowed you today. either working together on an article is useful and enjoyable or just irratating. If the former, lets carry on, if the latter then we let each other edit an article by themselves until done. Please add to the to-do list time-to-time; & we better remove items when we have that "good enough for now" feeling.

There has been bad blood between an editor and those he calls "mathpeople". That has been v divisive and led to the decline of WikiLogic.

This is an unfair characterization. Pontiff Greg Bard (talk) 15:48, 14 May 2008 (UTC)

Pontiff Greg Bard

Actually I'd say this is a generous characterization.

My last remark above described the drama rather than the actors. If bad blood and divisive are to overstate the problem, then constructive would be to err in the opposite direction. It has been suggested, that a reason for the inactivity of WikiProject Logic is that mathematical logic is in the process of cutting its ties to philosophy. Perhaps, perhaps, but that would be a matter for sociology, or history. Many matters once part of philosophy have left the nest, changed their names, and started families of their own. (Remember Natural Philosophy and Mental Philosophy?) Bless them, and wish them well! What I would like to see I say below. --Philogo 19:46, 15 May 2008 (UTC)

Philogo, I do not insult people directly as others very often do to me. It seems that there is a need by some to talk about how stupid and ignorant I am. All I ever claim is that there are things that I understand, which other people do not understand, and I am often surprised by it. As far as the "mathpeople" are concerned. That obviously isn't personal. Furthermore, it is an accurate characterization, and there has been at least some conciliation on that issue (although the strong bias isn't going away). I wish that there was discussion by others about the culture here when I first started. This way I would have known more about the pragmatic realities here sooner. I am going to have to make an effort to document these attacks on myself more completely, and wrestle them to the ground, lest we have this kind of impression that you have. Please relent. Pontiff Greg Bard (talk) 20:38, 20 May 2008 (UTC)

Gregbard. Just in case its not clear, the line begining "Actually" are not my words but an unsigned remark added today.

If you look back (I think on this page) you will find when I first joined this merry throng I was bemused about your account of how things had been for you editing. I had not imagined that editing articles on logic for an encyclopedia (with no OR) of all things could engender, how should I put it, such "colourful" exchanges. I imagined I could ignore all that and just write or edit the odd article from time to time. It is true that I have "scolded" you and other for being rude to one another and suggested we proceed with the cool quite voice of reason. I can imagine that such remarks can be irritating ("incredibably condescending" I think was one characterisation) but not, per se, rude. No offence to any party has been intended, to you or any others. I was cross when the Logic logo was abolished and articles split bewteen maths and philosophy and I admit that I thought you had a lot to do with it and have suggested as much on this page. I am sorry if that was unjust, but I am still cross and I still think it was misguided. You have asked me to relent; tell me what you would like me to do less of, or better still, more of (if its not "bugger off". (I wonder if that last will attract a WikiRepremand) If you wonder what I would like, it is still what I say below. Now cheer up! --Philogo 21:29, 20 May 2008 (UTC) (NB zero Sharp I have signed my comment.--Philogo 21:29, 20 May 2008 (UTC)

You are perfectly justified in being upset about the organization of wp:logic. I just don't know how to make everybody happy given the overlapping issues. I took the initiative, and now everyone is angrier than if I just did nothing. We at least have a place for "philosophical logic" (a distinction which meant almost nothing to me previously), whereas there was no place until that time.

I try to stay focused on the content and concepts. However, I receive more than my share of attacks. They aren't from you, however, you have joined in, when I wished you wouldn't. For the record, there is nothing more obvious to me than the fact that you and the others are perfectly intelligent, knowledgeable, competent, and wonderful people even if there is not complete understanding. I just wish that the tone wasn't wasn't so condescending against me all the time. The latest deletion from your talk page is the latest example, and a snipe at myself on talk:logical consequence was another. Be well. Pontiff Greg Bard (talk) 22:50, 20 May 2008 (UTC)

I would like to see joint effort on Logic articles of mutual interest to philosophers and mathematical logicians, and I suggest we call such just Logic articles. Articles which are purely/mainly philosophy of logic should be in that article. Take a look at it if you are that way minded. I think it would be better if people did not describe themselves as either mathematicans of philosophers (you will see that I never have: for all you know I am a BIV [ brain in a vat]) but instead just get on with editing articles if they are willing and able to do so.

Lets for now chat here from time to time on what next to do and how.--Philogo 13:38, 14 May 2008 (UTC)

[edit] Formal language (disambiguation)

I've removed the {{hangon}} tag with which you started this page. Rather counterintuitively, adding this tag in fact adds your page to the list of candidates for deletion! You'd be safer leaving it off until someone actually tags the page for deletion. I'm not certain of the function of this page right now: disambiguation pages usually consist of libks out to other articles, of which there are none here. Also, I'm not sure what purpose the page serves while the Formal language page seems to be pretty comprehensive. Disambig pages are usually needed for titles which have little or nothing in common with one another: see WP:D for more details. Let me know if I can help in making this page work the way you want it to. Kim Dent-Brown ^(Talk) 13:12, 25 May 2008 (UTC)

Thanks I tagged it hangon becase message said it was about to be deleted. The purpose of ths disambiguity page is discussed on the Formal language talk page, where you will see that various editors have claimed is is far form compprehensve, and it would appear there is a deal of talking at cross purposes becasue the term has apparenly different meanings in different sujects. JUST what a diambiguation page if intended to sort out, is it not? Cheers.--Philogo 13:17, 25 May 2008 (UTC)

Hi there, I'll read the talk page you refer to soon (just about to go out right now.) But in response to your last question: I think the answer is NO! A disambig page is to point people to articles with the same name but very different meanings - eg Mercury could refer to a planet, a metal, a space program and several other unrelated things. You're proposing a page about SIMILAR things with slightly differenty names and definitions, which is not a disambiguation page in the sense Wikipedia uses the term. Have a good read of WP:D for more information which may help in framing the page. Kim Dent-Brown ^(Talk) 13:30, 25 May 2008 (UTC)

Hi fair enough, but if the term IS ambiguus, then the article Formal language will need to be split and other atricles will be needed. So let it ride a while would you - otherwise the discussioon page for Formal language will go on and on with everybody talkinng at cross-purposes and getting cross with each other like an infernal tower of babel.--Philogo 13:36, 25 May 2008 (UTC)

IMHO the suggestion that the term Fromal Language has different meanings in the fields of logic, mathematical logic, mathematics, computer science, linguistics and philosophy is not proven (although this does not entail that it is not true, of course). It therefore seem unlikey that seperate articles will be forthcoming and therfore there is no need for the diambiguity page I created in anticipation. Thfore I have deleted it.--Philogo 00:04, 27 May 2008 (UTC)

[edit] Proposed deletion of Interpretation(disambiguation)

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[edit] Philosophy/Quotations

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