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Hermann Weyl in the SEP

Submitted by Richard Zach on Wed, 09/02/2009 - 9:00pm

Exciting new entry in the SEP on Hermann Weyl, by John Bell.

Logic on Your iPhone

Submitted by Richard Zach on Wed, 09/02/2009 - 4:15pm

David Johnston, of the University of Victoria Philosophy Department, has just released three apps for the iPhone (and iPod Touch), which will be of interest to students (and teachers) of introductory logic courses:

Logic 100

These utilities for truth-functional logic allow you to check syntax, construct truth tables, and test for consistency and validity. Notation can be set to match any logic textbook.


These utilities for categorical logic allow you to construct syllogisms, test them for validity, and display their Venn diagrams.

Logic 101

This app helps you construct derivations based on the system SD from The Logic Book. It checks the syntax of each line and automatically applies derivation rules. Completed derivations, including line justifications, can be emailed directly from the app.

I guess we'll have to be more vigilant about students having cellphones on them when they take a logic exam! But, in the words of Hans von Ditmarsch, "anyone who gets people to do logic while waiting for their bus, wasting time otherwise, ..., deserves praise!" Read more about these apps on, try them out, and let us (and him) know what you think!

Incidentally, these apps are versions of David's Logician's Toolkit, which lets you do all these things inside a Java applet on his website. Useful especially if you use the Logic Book.

Apology for Alan Turing

Submitted by Richard Zach on Tue, 09/01/2009 - 4:16pm

As you probably know, logic pioneer Alan Turing invented the Turing machine model of computation, proved the undecidability of the halting problem and (independently of Church) the undecidability of the decision problem, and played an important role in the work at Blechley Park that broke various German ciphers during World War II. He was also gay, and committed suicide following his criminal conviction for "gross indecency" and the chemical castration he was forced to undergo. There are now two petitions circulating, calling for a formal apology from the British Government for Turing's treatment: one for British citizens and an international petition.

Books by Russell (and others) in Google Books

Submitted by Richard Zach on Tue, 09/01/2009 - 1:45am

I had to look up a Russell quote the other day, and that's when I noticed that many of his books -- including the Foundations of Geometry, Our Knowledge of the External World, Introduction to Mathematical Philosophy, Analysis of Mind, Principles of Mathematics, Mysticism and Logic, and Principia Mathematica (annoyingly, only vol. II) -- are available in their full glory through Google Books. There are lots of other gems, including Hilbert's Grundlagen der Geometrie, the Tractatus, etc. But beware: the Google metadata are unreliable, to say the least (see Geoff Nunberg on Google Books: A Metadata Trainwreck).

Job Prospects for Philosophy Students

Submitted by Richard Zach on Fri, 08/28/2009 - 3:34pm

Here's another article in the "you might not have thought it but philosophy undergrads are actually doing well in careers in business and law" mold, from a Canadian perspective.

Philosophy’s makeover: Why job prospects for philosophy grads are brightening, by Daniel Drolet

T-Rex on Vagueness

Submitted by Richard Zach on Fri, 08/28/2009 - 3:24pm

Carbone on the Genus of Proofs

Submitted by Richard Zach on Mon, 08/24/2009 - 5:19pm

A long time ago I posted on Richard Statman's dissertation work on the geometrical complexity of proofs: take a proof in natural deduction, interpret the formulas in it as nodes of a graph with edges going from premise to conclusion of an inference and from assumption to the (conclusion of the) inference where it is discharged. The genus of that graph is an interesting complexity measure. Ale Carbone has also worked on this complexity measure, and now has an exciting paper entitled "Logical structures and genus of proofs" forthcoming in the Annals of Pure and Applied Logic. Here's the introduction:

The objects of our analysis are proofs. We shall not ask why we prove a statement, nor how to show a statement, but how difficult it is to prove it. An answer to the third question might give insight into the second.

At present, there is no notion that captures well how difficult it is to prove a theorem. Measures employed to grasp this idea are the number of steps and symbols used in a deduction, and these measures are far too rough: proofs containing no cuts/lemmas usually have a larger number of steps and symbols than proofs with cuts, but their combinatorial structure is simple, essentially a tree; on the other hand, the combinatorial structure of proofs with cuts can be quite intricate, and lemmas might be very hard to guess. Despite this, in practice, we look for lemmas in order to show a theorem.

Here we consider the genus of a proof as a measure of proof complexity and we discuss a few geometrical properties of logical flow graphs of proofs, with and without cuts, with the purpose of representing how complicated a cut-free proof can be. The main result of the article says that arbitrarily complicated non-oriented graphs, that is graphs of arbitrarily large genus, can be encoded in a cut-free proof. This fact was proved by Richard Statman in his thesis written in the early seventies and never published. Here, we reformulate Statman’s result in a purely graph theoretical language and give a proof of it. We show that there are several ways to embed non-oriented graphs of arbitrary complexity into cut-free proofs and provide some other direct embeddings of arbitrarily complex non-oriented graphs into proofs possibly with cuts. We also show that, given any formal circuit, we can codify it into a proof in such a way that the graph of the circuit corresponds to the logical flow graph of the encoding proof.

Logic (and Other Fun Stuff) on BBC Radio 4

Submitted by Richard Zach on Mon, 08/03/2009 - 9:26pm

The BBC 4 radio program "In Our Time," presented by Melvyn Bragg, has archives of previous features on a range of topics, including some relevant to logic. Haven't had the time to listen to them, but it you do, let me know what you think. Might be the kind of thing you can tell your relatives to listen to when they want to know what you are interested in.

HT: Chris Green

New Open Access Logic Books from the ASL

Submitted by Richard Zach on Sun, 08/02/2009 - 10:21pm

Exciting developments! The Association of Symbolic Logic has made the now-out of print volumes in the Lecture Notes in Logic (vols. 1-12) and Perspectives in Mathematical Logic (vols. 1-12) open-access through Project Euclid. This includes classics like

I'm especially excited about the Hájek/Pudlák and Barwise/Feferman volumes, which are chock-full of useful material! Check out the full list of volumes available (click on the "Series Contents" link on the right side). For now it's available in nicely scanned and OCR'd PDF format, perhaps there will also be a print-on-demand way of getting a bound copy.

Most Logical Countries in the World

Submitted by Richard Zach on Tue, 07/14/2009 - 7:49pm

For your amusement: a list of all countries with at least 5 members of the Association for Symbolic Logic, rank-ordered by number of logicians per 10,000,000 inhabitants. Bonus info: percentage of women logicians in these countries.

Country # ASL members % Women per 10,000,000
New Zealand 17 0% 39.5
Switzerland 25 4% 32.5
Israel 22 18% 29.7
Norway 13 0% 27.1
USA 806 12% 26.3
Netherlands 43 21% 26.1
Canada 85 11% 25.2
Belgium 23 4% 21.5
Finland 10 10% 18.9
United Kingdom 100 10% 16.4
Denmark 9 0% 16.4
Sweden 15 20% 16.3
Singapore 7 17% 14.6
Greece 16 25% 14.3
Austria 11 9% 13.3
Croatia 5 0% 11.4
Germany 87 8% 10.6
Portugal 9 33% 8.5
Australia 17 6% 7.8
Spain 35 11% 7.6
Italy 42 24% 7.0
France 40 11% 6.2
Japan 63 12% 5.0
Czech Republic 5 0% 4.8
Poland 12 8% 3.1
Brazil 40 13% 2.1
Colombia 8 25% 1.8
Argentina 6 33% 1.5
South Africa 6 0% 1.2
Iran 5 0% 0.7
Russia 8 25% 0.6
Mexico 5 20% 0.5
China 14 0.1
India 8 20% 0.1

Women in Philosophy of Logic and Philosophical Logic

Submitted by Richard Zach on Fri, 06/26/2009 - 4:24pm

Catarina Dutilh Novaes sent the following important message to PHILOS-L last weekend, reposted here with her permission:

Dear all,

Recently (and admittedly very late!), I started thinking more seriously about the lack of gender balance in the areas in which I do most of my research, namely history and philosophy of logic and philosophical logic. What got me thinking was probably the (positive) noise being made at Feminist Philosophers. One of the issues raised by the Feminist Philosophers is the low proportion of women in most philosophy conferences (in particular as invited/keynote speakers); I realized that in the workshop I am organizing, there are only three women as speakers, including myself! So I think this is a matter that deserves further attention.

Richard Zach had a blog entry a while ago on the staggeringly low number of women publishing in the journals of the area (his data concerned the Journal of Philosophical Logic). From this sort of data it is all too easy to conclude that there simply aren't enough women around working in (philosophy of) logic and philosophical logic so as to redress the imbalance seen in conference lineups. But here again the usual analysis applies: the lack of female speakers at such conferences reinforces the idea that the area is just not 'for women', which in turn does not encourage young female students to pursue interests they might have in the area. Absence of female keynote speakers may also be a discouraging factor for other female researchers to submit papers to such conferences. Sally Haslanger has a wonderful piece on how vicious these mechanisms can be, which can be found here: Changing the Ideology and Culture of Philosophy: Not by Reason (Alone)

So the purpose of this message now is to question the widespread impression that there are not (or very few) prominent female logicians and philosophers of logic, people with the standing to be keynote speakers at major conferences. I was thinking it might be useful to compile a list of such people, sort of a handy device that could help those organizing conferences in the area to ensure a better gender balance among the speakers. Please send me names off list, and I will post the results to the whole list once we have a significant number of names. Just to give you an idea of what I have in mind, here are some women that would obviously be on such a list: Juliet Floyd, Penelope Maddy, Gila Sher, Delia Graff Fara. I’m sure there are many more such talented women working in the philosophy of logic and philosophical logic, so I look forward to many reactions!


cdutilhnovaes at yahoo dot com

Please respond to Catarina at the email address above!

UPDATE: Results of the effort are collected "women in philosophy of logic and philosophical logic" on the Logic and Rational Interaction blog.

PM@100: Logic from 1910 to 1927

Submitted by Richard Zach on Wed, 06/24/2009 - 1:28am
Call for Papers
PM@100: Logic from 1910 to 1927

21 – 24 May, 2010
Bertrand Russell Research Centre
McMaster University
Hamilton, Ontario

The Bertrand Russell Research Centre in 2010 will host a conference to celebrate the 100th anniversary of the publication of the first volume of Russell and Whitehead’s Principia Mathematica.

The publication in 1910 of the first of the three volumes of Russell and Whitehead’s Principia Mathematica was a landmark in the development of logic, the foundations of mathematics, and the application of logic in philosophy. The rapid development of these fields in the two decades after 1910 owes perhaps more to Principia Mathematica than to any other work. Subsequently, however, its lessons learnt in different ways by different people, it becomes more difficult to determine exactly what the world owes to this gigantic piece of work. Daunting both for its size and its technical difficulty, the book is now known more by reputation than by detailed study. Russell himself maintained, no doubt with some exaggeration, that he knew of only six people besides the authors who had read the entire three volumes. He remained dissatisfied with the foundations of the work and attempted a major revision (this time without Whitehead’s help) in a second edition published in 1925–27, which further complicated its historical legacy.

A century after its first appearance, a great deal has changed. Many of Russell’s working papers on the problems it addressed have been published, and this has led to significant re-interpretations of the work itself. Enough time has now passed to make it possible to evaluate what contributions it made, or failed to make, to philosophy, logic, and the foundations of mathematics.

Presenters Include: Patricia Blanchette, Charles Chihara, Warren Goldfarb, Ivor Grattan-Guinness, Leila Haaparanta, Allen Hazen, David Kaplan, Gregory Landini, Peter Simons, Alasdair Urquhart, and Richard Zach.

Submissions to the conference are sought in all areas relating to Principia Mathematica or to the development of logic and to the philosophy and foundations of mathematics in the years between the two editions.

Contributors are asked to submit two copies of an essay suitable for 30–45 minute presentation with an abstract no later than 1 January 2010 to:

Professor Nicholas Griffin, Director
The Bertrand Russell Research Centre
1280 Main Street West
Hamilton, Ontario

FAX: 905-577-6930

Graduate students are also encouraged to submit. Announcements of acceptances for the program will be made by the end of February 2010.

Conference Co-Organizers:

Nicholas Griffin
The Bertrand Russell Research Centre
McMaster University

Bernard Linsky
Department of Philosophy
University of Alberta
bernard.linsky@ualberta. ca

Server Problems

Submitted by Richard Zach on Fri, 06/19/2009 - 6:40pm

My website people changed something on the server and now this blog isn't displaying properly and my website is completely down. Sorry. If you want to get to my website, try instead of

Benson Mates, 1919-2009

Submitted by Richard Zach on Tue, 05/19/2009 - 8:11am

Benson Mates, Professor emeritus of Philosophy at the University of California, died May 14. He was a logician, historian of logic, philosopher of language,epistemologist, Leibniz scholar, and author of the excellent logic textbook Elementary Logic.

Carnap Action in Paris

Submitted by Richard Zach on Sat, 05/16/2009 - 6:34am

In between thinking and lecturing about the epsilon-calculus, I'm in Paris for a few days: it's where all the Carnap action is right now. Heard wonderful talks by the likes of Steve Awodey, Dan Isaacson, Alan Richardson, Erich Reck, Delphine Chapuis-Schmitz, and Tom Uebel, unfortunately missed those by Michael Beaney, Juliet Floyd, and Rick Creath, and looking forward to some by André Carus, Gottfried Gabriel, Peter Hylton, Thomas Morman, and Pierre Wagner today. Thanks to Pierre for putting on this exciting conference!

Robert K. Meyer, 1932-2009

Submitted by Richard Zach on Sat, 05/09/2009 - 12:47pm

Bob Meyer, emeritus professor of logic and philosophy at ANU, died last Thursday at the age of 77. He worked mainly on relevant logics and entailment, and is remembered not just for his work in logic, but also his wit and humor.

Dave Chalmers and Greg Restall remind us of the paper "God exists!", in which Bob proved that the existence of God is equivalent to the Axiom of Choice, and the Manifesto of the Logician's Liberation League.

UPDATE: Obit from the ASL Newsletter:

Robert Kenneth (Bob) Meyer, a major contributor in the field of non-classical logics, and a central figure on the Australasian logical scene, died in Canberra on May 6, 2009 at the age of 76, after a long struggle with cancer. Before his retirement as Professor in 1998, Meyer spent more than twenty years at the Australian National University, first in Philosophy at the Research School of Social Sciences, and subsequently in the Automated Reasoning Project, of which he was a founder. Meyer was born on May 27, 1932 in Philadelphia. He received a Bachelor of Divinity at Princeton Theological Seminary in 1956. After studying Japanese in Kyoto, he served as a missionary at the Christian Institute of Industrial Relations in Osaka from 1959 to 1962. Impelled by questions about the foundations of his religious beliefs, he enrolled as a graduate student in Philosophy at the University of Pittsburgh, receiving a Ph.D. in 1966 under the supervision of Nuel Belnap. From 1965 to 1974, he taught in Philosophy departments at West Virginia University, Rice University, Bryn Mawr College, Indiana University, and the Universities of Toronto and Pittsburgh. From 1974 until his retirement in 1998, he was at the Australian National University. Meyer served as the President of the Australasian Association for Logic in 1982 and was elected as a Fellow of the Australian Academy of the Humanities in the same year. Meyer was famous for his work in relevant logic and entailment. An early major contribution in the area was his proof (with J.M. Dunn) of the admissibility of the rule $\gamma$ in the logics $R$ and $E$. His best known work in the area is his series of papers with Richard Routley, expounding the relational semantics for relevant logics, and proving completeness theorems and many other results with its aid. Bob Meyer's brilliance as a logician and his infectious enthusiasm stimulated the growth of the Australian school of logic. In the 1980s, the research group surrounding him pioneered the use of computers in investigating logical problems. This group formed the nucleus of the Automated Reasoning Project, that later morphed into the Logic and Computation Group (both at ANU). Bob was noted not only for his enormous and unquenchable enthusiasm for logic, but also for his wit and humour. From 1969 onwards, he was the Maximum Leader of the Logicians Liberation League; for the manifesto of the LLL see Remarkable also is his contribution to rational theology, "God Exists!'' (published in Noûs 21: 345-61, 1987), in which he proves that God's existence (under a certain interpretation) is equivalent to the Axiom of Choice. Bob is remembered fondly by his family and his many friends and colleagues as a remarkable logician, and a wonderful human being.

Submitted by Richard Zach on Fri, 05/08/2009 - 6:55am

Vienna Waits For Me

Submitted by Richard Zach on Tue, 05/05/2009 - 3:50am

At least I hope it does. I'll see in a couple of days, when I get there. Scheduled to give a talk on proof interpretations at the Institute Vienna Circle on Thursday (5 pm, Institut für Zeitgeschichte, Uni Wien Campus, Hof 1, 2. Stock, links). Friday, I start teaching a short course on the epsilon calculus at the TU Wien Logic Group. It'll be 10-2 in the seminar room of the department, 185/2, Favoritenstrasse 9, 3rd floor, yellow zone. Both of those will be in English, contrary to what you might think from the content of the linked pages.

Women in Philosophy Employment Study Online

Submitted by Richard Zach on Wed, 04/29/2009 - 11:15pm

The May 2009 issue of the Proceedings and Addresses of the APA contain an interesting study conducted by the Committee on the Status of Women. It's online on the APA website:

CSW Jobs for Philosophers Employment Study