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Submitted by Richard Zach on Sat, 01/31/2015 - 12:55pm

Tools for Teaching Logic (June 9-12, 2015, Rennes, France) is seeking original papers with a clear significance in the following topics (but are not limited to): teaching logic in sciences and humanities; teaching logic at different levels of instruction (secondary education, university level, and postgraduate); didactic software; facing some difficulties concerning what to teach; international postgraduate programs; resources and challenges for e-learning logic; teaching argumentation theory, critical thinking and informal logic; teaching specific topics, such as modal logic, algebraic logic, knowledge representation, model theory, philosophy of logic, and others; dissemination of logic courseware and logic textbooks; teaching Logic Thinking.

Abstracts are due on February 13, full papers on February 20. More details on the website: http://ttl2015.irisa.fr/

Submitted by Richard Zach on Sat, 01/31/2015 - 10:45am

In case you need the original 1920 or 1923 papers by Skolem, and you don't have *Selected Works in Logic* handy, here are PDFs extracted from the digital version of *Skrifter utgit av Videnskapsselskapet i Kristiania. I, Matematisk-naturvidenskabelig klasse* made available by the Biodiversity Heritage Library and the Internet Archive.

Thoralf Skolem, "Logisch-kombinatorische Untersuchungen über die Erfüllbarkeit oder Beweisbarkeit mathematischer Sätze nebst einem Theorem über dichte Mengen", *Skrifter utgit av Videnskapsselskapet i Kristiania. I, Matematisk-naturvidenskabelig klasse* 1920, no. 4, pp. 1–36

Thoralf Skolem, "Begründung der elementaren Arithmetik durch die rekurrierende Denkweise ohne Anwendung scheinbarer Veränderlichen mit unendlichem Ausdehnungsbereich", *Skrifter utgit av Videnskapsselskapet i Kristiania. I, Matematisk-naturvidenskabelig klasse* 1923, no. 6, pp. 1–38.

Submitted by Richard Zach on Sat, 01/31/2015 - 9:27am

Submitted by Richard Zach on Sun, 01/18/2015 - 8:25am

European Summer Meeting of the Association for Symbolic Logic

Helsinki, Finland, 3-8 August 2015

http://www.helsinki.fi/lc2015

The annual European Summer Meeting of the Association for Symbolic Logic, the Logic Colloquium 2015 (LC 2015), will be organized in Helsinki, Finland, 3-8 August 2015. Logic Colloquium 2015 is co-located with the 15th Conference of Logic, Methodology and Philosophy of Science, CLMPS 2015, and with the SLS Summer School in Logic.

Toshiyasu Arai (Chiba)

Sergei Artemov (New York)

Steve Awodey (Pittsburgh)

Johan van Benthem (Amsterdam and Stanford)

Artem Chernikov (Paris)

Ilias Farah (York)

Danielle Macbeth (Haverford)

Andrei Morozov (Novosibirsk)

Kobi Peterzil (Haifa)

Ralf Schindler (Münster)

Saharon Shelah (TBC) (Jerusalem and Rutgers)

Sebastiaan Terwijn (Nijmegen)

Erich Grädel (Aachen)

Menachem Magidor (Jerusalem).

**Set Theory**, organized by Heike Mildenberger (Freiburg)

**Model theory, **organized by Dugald Macpherson (Leeds)

**Computability Theory, **organized by Russell Miller (New York) and Alexandra Soskova (Sofia)

**Proof Theory, **organized by Benno van den Berg (Amsterdam) and Michael Rathjen (Leeds)

**Philosophy of Mathematics and Logic, **organized by Patricia Blanchette (Notre Dame) and Penelope Maddy (Irvine)

**Logic and Quantum Foundations, **organized by Samson Abramsky (Oxford)

Travel awards for students and young researchers have been made available by the organizers. In some cases full compensation of expenses is possible. The website includes detailed information about the awards, instructions of how to apply, and an electronic form which may be used for the application.

The Logic Colloquium will include contributed talks of 20 minutes' length. Abstracts on contributed talks are published in the *Bulletin of Symbolic Logic*.

The deadline for travel award applications and abstract submission is **Tuesday, May 3, 2015**. Please see http://www.helsinki.fi/lc2015/submission.html for information about applying for travel awards and for submitting an abstract.

Submitted by Richard Zach on Fri, 01/16/2015 - 10:36am

Sad news from Philip Welch at Bristol: John Shepherdson has died.

I deeply regret having to impart the very sad news that John Shepherdson died in Bristol on Thursday of an inoperable sarcoma.

John was a founder of the BLC (together with Robin Gandy if I remember rightly). His own work was in many areas, starting with set theory, then recursion theory (inventing the register machine in a paper with Sturgis), models of arithmetic, incompleteness phenomena, and towards the end of his career working on PROLOG and fuzzy logic. Besides all this, he made Bristol a centre for mathematical logic in the UK, with many prestigious visitors in the early years. In particular it became a training ground in the 50s, 60s for many who went on to academic careers, as well as in the 70's through its MSc in Mathematical Logic and Theory of Computation. He spent his whole working career at the Bristol department arriving there in 1946.

He always struck me as an exceptionally kind person, an amusing and intelligent companion to be with, and most modest, as well as self-effacing in the best sense. He will be much missed.

A fuller appreciation will be composed at some point. There will be no funeral, but his family have indicated there will be a Memorial Service or Occasion at a date in the future, when a full tribute can be paid to him.

Philip Welch

Submitted by Richard Zach on Fri, 01/16/2015 - 8:35am

Every mathematician and philosopher should watch this video by Sarah-Jane Leslie (Philosophy, Princeton) on her study with Andrei Cimpian (Psych, Illinois). Takes just 11 minutes.

Then you can go and read the original study in *Science* or any of the writeups in, e.g., the Science news blog, Chronicle, Daily Nous, etc.

Submitted by Richard Zach on Fri, 01/09/2015 - 1:54pm

The Stanford Encyclopedia of Philosophy now has entries on:

- Negation (Laurence R. Horn and Heinrich Wansing)
- Disjunction (Ray Jennings and Andrew Hartline)
- Indicative Conditionals (Dorothy Edgington)
- Quantifiers and Quantificiation (Gabriel Uzquiano)
- Identity (Harold Noonan and Ben Curtis)

Submitted by Richard Zach on Wed, 01/07/2015 - 7:02am

I learned today that Ivor Grattan-Guinness, the historian of mathematics and logic, died last month.

Obituaries:

Submitted by Richard Zach on Mon, 12/22/2014 - 1:09pm

If you're using BibTeX and LaTeX and are doing any kind of scholarly/humanistic work, I'm sure you've run into this annoying problem: BibTeX always complains when a book has both an author and an editor. That's a problem when, say, you want to include

Gödel, K., 1986. *Collected Works*, vol. I. S. Feferman et al., eds. Oxford: Oxford University Press.

There is a wonderful package that allows you to generate new BibTeX bibliography styles based on a large number of customization options: custom-bib. It comes with one big master bibliography style merlin.mbs from which your custom style is generated. I've produced a modified file which will also print both author and editor for a book that has both.

Merry Christmas.

Submitted by Richard Zach on Sun, 12/14/2014 - 7:19am

New in the *Review of Symbolic Logic* (part 1, part 2)

A Gödel sentence is often described as a sentence saying about itself that it is not provable, and a Henkin sentence as a sentence stating its own provability. We discuss what it could mean for a sentence of arithmetic to ascribe to itself a property such as provability or unprovability. The starting point will be the answer Kreisel gave to Henkin’s problem. We describe how the properties of the supposedly self-referential sentences depend on the chosen coding, the formulae expressing the properties and the way a fixed points for the formulae are obtained. This paper is the first of two papers. In the present paper we focus on provability. In part II, we will consider other properties like Rosser provability and partial truth predicates.

Submitted by Richard Zach on Sat, 12/13/2014 - 6:19am

Submitted by Richard Zach on Sat, 12/13/2014 - 5:51am

In response to my post about "lesser known Russian/Soviet logicians", Lev Beklemishev commented:

Dirk van Dalen was interested in Shatunovsky's work and at his request I procured a copy of his book on the development of algebra on the basis of what can be called rudimentary constructivist ideas. This was, of course, pre-Brouwerian, and the ideas of Shatunovsky were perhaps more in line with Kronecker's. In any case, this was interesting to see, but it never came to a publication on it with Dirk.

Yanovskaya was his most well-known student, and she was well-respected among the mathematical logicians in Moscow, for whom she effectively provided some sort of ideological cover in the later years. She worked at the department of mathematics at MSU and is well-remembered there.

A good informative article on Shatunovsky is his obituary written by Chebotarev and published, I think, in Uspekhi matematicheskih nauk [link].

By email, Mark van Atten wrote:

A marginal note: There was a brief epistolary exchange between Kagan and Brouwer. They had been put in contact by Mrs Ehrenfest-Afanassjewa. Kagan's letter to Brouwer of June 22, 1922 can be found in

The Selected Correspondence of L.E.J. Brouwer(ed. Van Dalen, Springer 2011), pp. 290-291. In that letter Kagan also mentions Schatunowsky (as he, writing in German, spells it) and the latter's work on the development of algebra without the excluded middle.The date as given by Van Dalen there is 1925. The online-edition of the correspondence at extras.springer.com, which contains all of Brouwer's remaining correspondence (but untranslated), contains that letter twice, once dated 1922, once 1925. 1922 seems to me to be correct as Ehrenfest-Afanassjewa's request to Brouwer to send some material to Kagan was made in that year.

That online edition also includes a short second letter from Kagan, dated Feburay 8, 1925 (on Alexandrov and Urysohn, but without specifically scientific content).

The online edition mentions Shatunovsky once more, in a letter from Alexandrov to Brouwer of March 15, 1927. Commenting on a paragraph in a letter from Brouwer to him, apparently lost, of December 27 [1926], Alexandrov writes: `Im Absatz 8 äussern Sie mir Ihre Meinung über den unsinnigen Artikel von Schatunowski. Da diese Meinung im Stillen auch immer die meinige war, sah ich keinen Grund mich irgendwie dazu zu äussern, und habe mich begnügt, dieselbe an Frau Ehrenfest zur gefälligste Kenntnisnahme mitzuteilen.'

Alas, the online edition contains no mention of Schönfinkel.

Lev responded:

This is an interesting exchange. Is there a way to find out which paper of Shatunovsky was mentioned by Brouwer and Alexandroff as non-sensical? In any case, this assessment could actually be true. From a rather superficial reading of his long work I got the impression that it was a specific way of presenting rather ordinary algebra, without anything revolutionary, accompanied by an introduction stating some philosophical pre-constructivist motivations. The case for doing all this was not a very strong one. But it could well be that they mention some other work that could be either more or less non-sensical that this.

By the way, Kagan was the grandfather of Yakov Sinai, this year's Abel laureate. I have just watched his interview where he told some story about his grandfather and his friend Shatunovsky from their time in Odessa. Apparently he knows a lot about their lives! These coincidences are quite curious...

Mark responded to Lev's question:

The edition of Brouwer's correspondence does not carry an annotation on this point, unfortunately. Perhaps an educated guess can be made from a full bibliography. Is there one?

The interview Lev mentioned is on youtube. It's in Russian, and Google Translate didn't do a very good job on the transcript, probably because of missing punctuation. I'm attaching it here in case someone wants to play with it.

Submitted by Richard Zach on Tue, 12/09/2014 - 8:42am

I'm working on a paper that features Moses Schönfinkel, so I was reading through a manuscript of his where he rattles off a long list of important logicians. In addition to the usual suspects, it features the names "Schatunowski, Sleschinski, Kahan, Poretski." I spent the better part of a day trying to figure out to whom he was referring:

Samuil Osipovich Shatunovsky (1859-1929) was a mathematician working in Odessa who, so Wikipedia, "independently from Hilbert, he developed a similar axiomatic theory and applied it in geometry, algebra, Galois theory and analysis."

Ivan Vladislavovich Sleshinsky (1854-1931), or Jan Śleszyński in Polish, was an analyst who also wrote on logic who worked in Odessa, where Schönfinkel was his student, and later Krakow. He also translated Couturat's book *The algebra of logic* into Russian.

Platon Sergeevich Poretsky (1846-1907) worked on Boolean algebraic logic, teaching in Kazan. He's credited with being the first mathematician to teach logic in Russia.

Kahan was a little harder to track down, but apparently Kahan is an alternative transcription of Ка́ган:

Veniamin Fedorovich Kagan (1869-1953) was a geometer and expert on Lobachevsky, who studied in Odessa, Kiev, and St. Petersburg, and worked in Moscow. He grew up in the same city as Schönfinkel, Yekaterinoslav (now Dnipropetrovsk).

In the process of googling about I also happened on Sofya Aleksandrovna Yanovskaya (1896-1966). She studied in Odessa at the same time as Schönfinkel and, like him, was a student of Shatunovsky. She was active in the revolution, and earned a doctorate in 1935 from Moscow State University, where she taught from 1931. In 1943 she founded the the seminar in mathematical logic. According to some sources, she became the first chair of the newly created Department for Mathematical Logic in 1959, however, others as well as the webpage of the institute have A. A. Markov as the first chair, 1959-1979. From this biography, in addition to her teaching and research in mathematics, she was influential in other interesting ways:

Her work in history and philosophy of mathematics included preparation of a Russian edition of Marx's mathematical manuscripts and the study of Marx's philosophy of mathematics, as well as more general study of philosophy of mathematics. She was interested, for example, in the history of the concept of infinitesimals and her work along these lines included a study of Rolle's contributions. She also paid special attention to the role of Descartes, and in particular to his

La Géométrie, in the development the axiomatic approach to mathematics. Her contributions to history and philosophy of logic included work on the problematics of mathematical logic, including problematics related to cybernetics. In the latter regard, an example can be found in the Russian translation of Alan Turing's essay "Can A Machine Think?", which she edited, and in whose introduction she contributed to the discussion of problems in the philosophical aspects of cybernetics through her original analysis of the comparison of the potentialities of man versus machine. She was also instrumental in acquainting Soviet logicians with the work of their Western colleagues through the translation program which she organized, that included the textbooks on mathematical logic of Hilbert and Ackermann, Goodstein, Church, Kleene, and Tarski, and for which she provided important interpretive introductions. She also wrote important and massive historical-expository surveys of Soviet work in mathematical logic and foundations of mathematics.

A special issue of *Modern Logic* was devoted to her life and work on the occasion of her centenary in 1996; it includes highly interesting articles on her work as well as some smaller biographical items (all open access). Another interesting paper is here.

UPDATE: Follow-up here.

Submitted by Richard Zach on Mon, 12/08/2014 - 7:29am

Shawn Standefer has done us all a great service by starting and populating a Wiki of PhD programs in Philosophical Logic!

This wiki provides an unranked list of PhD (and (eventually) terminal M.A.) programs that have strengths in philosophical logic. Links are provided to the websites, CVs, and PhilPapers profiles of the relevant faculty at each program. Additionally, when known, the specialities and willingness of faculty members to work with new graduate students are noted. The primary intended audience is prospective or current graduate students with interests in philosophical logic who want to get the lay of the land by seeing who works where, and on what. This wiki is modeled on Shawn A. Miller’s PhilBio.net wiki.

It's a wiki, so you can edit it: add programs, faculty in your program, edit your own specialities, add a link to your PhilPapers page, etc.!

Submitted by Richard Zach on Sat, 12/06/2014 - 11:06am

...is another's modus tollens.

[W]hen I was nine years old, I came down with scarlet fever. [...] During that year there was nothing in the world which I wanted so much as a bicycle. My father assured me that when I got well I would get one but, childlike, I interpreted this as meaning that I was not going to get well.

Julia Robinson, in: Constance Reid, The Autobiography of Julia Robinson. *The* *College Mathematics Journal*, Vol. 17, No. 1, (1986), pp. 3-21

Submitted by Richard Zach on Sat, 12/06/2014 - 9:25am

Jan Zygmunt and Robert Purdy have a paper ("Adolf Lindenbaum: Notes on his Life, with Bibliography and Selected References", open access) in the latest issue of *Logica Universalis* detailing what little is known about the life of Adolf Lindenbaum (1904-1941). It includes a complete bibliography of Lindenbaum's own publications and public lectures, as well as a bibliography of articles in which results are credited to Lindenbaum. Another paper on Lindenbaum's mathematical contributions is in the works.

The entire issue is dedicated to Lindenbaum. Jean-Yves Beziau gives this poignant quote in the introduction:

A mathematician, a modern mathematician in particular, is, as it would be said, in a superior degree of conscious activity: he is not only interested in the question of the what, but also in that of the how. He almost never restricts himself to a solutiontout courtof a problem. He always wants to have the most ??? solutions. Most what? The easiest, the shortest, the most general, etc.

Lindenbaum was murdered by the Nazis in 1941, at age 37.

Submitted by Richard Zach on Tue, 12/02/2014 - 7:56am

*Interpreting Gödel: Critical Essays*, edited by Juliette Kennedy, was just published by Cambridge. It looks extremely interesting, with an all-star cast of contributors:

1. Introduction: Gödel and analytic philosophy: how did we get here? Juliette Kennedy**Part I. Gödel on Intuition:**

2. Intuitions of three kinds in Gödel's views on the continuum, John Burgess

3. Gödel on how to have your mathematics and know it too, Janet Folina**Part II. The Completeness Theorem:**

4. Completeness and the ends of axiomatization, Michael Detlefsen

5. Logical completeness, form, and content: an archaeology, Curtis Franks** Part III. Computability and Analyticity:**

6. Gödel's 1946 Princeton bicentennial lecture: an appreciation, Juliette Kennedy

7. Analyticity for realists, Charles Parsons**Part IV. The Set-theoretic Multiverse:**

8. Gödel's program, John Steel

9. Multiverse set theory and absolutely undecidable propositions, Jouko Väänänen**Part V. The Legacy:**

10. Undecidable problems: a sampler, Bjorn Poonen

11. Reflecting on logical dreams, Saharon Shelah.

Submitted by Richard Zach on Fri, 11/28/2014 - 10:49am

Gödel's incompleteness theorems have many variants: semantic vs. syntactic versions, which specific theory is taken as basic, what model of computability is used, which logical system is assumed to underlie the provability relation, how syntax is arithmetized, what hypotheses the theorem itself uses (soundness, consistency, $\omega$-consistency, etc.). These result in trade-offs regarding simplicity of the proof, but also scope of application and consequences that can be drawn.

There are two new(ish) and super-useful surveys of proofs of Gödel's incompleteness theorem that review these versions and their limitations and scope. The first is by Lev Beklemishev:

Л.Д. Беклемишев (2010). Теоремы Гёделя о неполноте и границы их применимости. I., Успехи Математических Наук 65(5) 61-104. PDF.

English translation:

L. D. Beklemishev (2010). Gödel incompleteness theorems and the limits of their applicability. I.*,* *Russian Mathematical Surveys * 65(5) 857-898. PDF

The second is by Bernd Buldt:

B. Buldt (2014). The scope of Gödel’s first incompleteness theorem, *Logica Universalis*. forthcoming. PDF preprint

Lev's is mathematically more exhaustive and more technical; Bernd's is less technical and also goes into philosophically relevant aspects such as Gödel's theorems for system with non-classical underlying logics.

Submitted by Richard Zach on Fri, 11/28/2014 - 8:52am

Via the APMP list:

Expressions of interest are invited for a postdoc grant (financed by Junta de Andalucia) associated with the following research project:“THE GENESIS OF MATHEMATICAL KNOWLEDGE: COGNITION, HISTORY, PRACTICES” (P12-HUM-1216). IP: Jose FerreirosContact: josef@us.esThe grant consists in a 2-year research contract to be held at the University of Sevilla. Salary is in the range of 84000 euros for 24 months. Holders must have obtained their PhD before start of the grant,[update:] by 2014and at most 10 years ago (exceptions apply in case of motherhood). They will be doing research along the lines of this interdisciplinary project -- devoted to philosophy of mathematics, links between cognition and mathematical practice, and the interactions logic/mathematics and physics/mathematics. Knowledge of Spanish is desirable, although it is not a formal requirement.The call for these grants, issued by Junta de Andalucia, will be open from early December, allowing for only 15 days. Applications will be made to the Junta de Andalucia, but we invite candidates to get in touch with the project IP in advance, so that we can coordinate and assist you. If you are interested in applying, please contact the IP by email as soon as possible, explaining briefly your situation and interests. Keep in mind that the selection will be made on the basis of fit between the candidate's research project and the topic of the project.

Submitted by Richard Zach on Tue, 11/18/2014 - 7:05pm

Dana Scott's proof reminded commenter "fbou" of Kalmár's 1935 completeness proof. (Original paper in German on the Hungarian Kalmár site.) Mendelsohn's *Introduction to Mathematical Logic* also uses this to prove completeness of propositional logic. Here it is (slightly corrected):

We need the following lemma:

Let $v$ be a truth-value assignment to the propositional variables in $\phi$, and let $p^v$ be $p$ if $v(p) = T$ and $\lnot p$ if $v(p) = F$. If $v$ makes $\phi$ true, then \[p_1^v, \dots, p_n^v \vdash \phi.\]

This is proved by induction on complexity of $\phi$.

If $\phi$ is a tautology, then any $v$ satisfies $\phi$. If $v$ is a truth value assignment to $p_1, \dots, p_n$, let $\Gamma(v,k) = \{p_1^v, \dots, p_k^v\}$. Let's show that for all $v$ and $k = n, \dots, 0$, $\Gamma(v, k) \vdash \phi$. If $k = n$, then $\Gamma(v, n) \vdash \phi$ by the lemma and the assumption that $\phi$ is a tautology, i.e., true for all $v$. Suppose the claim holds for $k+1$. This means in particular $\Gamma(v, k) \cup \{p_{k+1}\} \vdash \phi$ and $\Gamma(v, k) \cup \{\lnot p_{k+1}\} \vdash \phi$ for any given $v$. By the deduction theorem, we get $\Gamma(v, k) \vdash p_{k+1} \to \phi$ and $\Gamma(v, k) \vdash \lnot p_{k+1} \to \phi$. By $\vdash p_{k+1} \lor \lnot p_{k+1}$ and proof by cases, we get $\Gamma(v, k) \vdash \phi$. The theorem then follows since $\Gamma(v, 0) = \emptyset$.

Notes:

- The inductive proof of the lemma requires as inductive hypothesis both the claim and the corresponding claim for the case where $v$ makes $\phi$ false (i.e., that then $p_1^v, \dots, p_n^v \vdash \lnot \phi$). Kalmár did not include the constants $T$ and $F$ in the language, but if you would, then Scott's (iii) would be a special case of the lemma.
- Scott's proof does not require the deduction theorem, but does require proof of substitutability of equivalents.