Submitted by Richard Zach on Thu, 06/29/2006 - 6:28am
Submitted by Richard Zach on Fri, 06/23/2006 - 12:58pm
Friendster reminded me that today is Alan Turing's birthday.
Submitted by Richard Zach on Thu, 06/22/2006 - 12:59pm
If you've ever coauthored a paper, you know what a hassle it is to send versions back and forth, keep track of changes, avoid conflicts when you're simultaneously changing things, and so on. Now software engineers have the same problems when working on large development projects and have developed very sophisticated Revision Control Systems. I've used the most well-known of these, CVS, for collaborating on a couple of papers. But CVS is not exactly easy to use, and for a larger project with more people who all use different systems (Linux, Mac, Windows) and who aren't as geeky as I, CVS is not a good choice. So: I'm looking for an easy way to collaborate on editing text documents. It should work cross-platform, it should have version control (keeping track of changes, ways of telling what parts of a document were edited by whom and when, reverting to previous versions), it should be easy to use (graphical user interface), it should be easy to install (preferably it should be completely distributed with the client programs doing all the work). It doesn't have to have fancy security, support for branching and merging projects, include a build environment, and all the other stuff that's important to programmers. I also don't want to have to set up a server or persuade my university's IT people to give accounts to my collaborators. Anyone have any ideas?
Submitted by Richard Zach on Thu, 06/22/2006 - 12:50pm
On June 22, 1936, Moritz Schlick, influential philosopher and center of the Vienna Circle of logical empiricists, was gunned down on the steps of the University of Vienna. The Institute Vienna Circle is holding a small memorial event at the University of Vienna today, which will include the presentation of the first two volumes of Schlick's Collected Works.
Submitted by Richard Zach on Wed, 06/21/2006 - 2:05pm
Submitted by Richard Zach on Thu, 06/15/2006 - 5:13pm
I'm at HOPOS, which is loads of fun. All my history of analytic/history of logic buddies are here. But more to the point:
Paolo Mancosu just gave the most amazing talk about the debate within the Vienna Circle about Tarski's theory of truth, in particular, the opposition that Neurath had voiced against it from the mid 1930s onward. I had always thought that the Vienna Circle wholeheartedly accepted Tarski's theory, and that Tarski's paper made truth an "acceptable" notion (from a logical empiricist standpoint). What Paolo showed, using correspondence between Carnap, Neurath, Tarski and others from 1935 and later, was that there was a debate raging over it. Neurath was opposed not, as one might suppose, because of the set theoretic metalanguage in which Tarski's theory was couched, but because he feared that people would use Tarski's theory in areas where it wasn't applicable, i.e., in non-formalized languages, and that it would lead people to return to "metaphysics". (I guess, that has actually happened decades later in the whole thing about deflationary conceptions of truth!) Moreover, we now know why no-one is aware about the tensions within the Vienna Circle around the theory of truth: at the Congrès Descartes in Paris in 1937, there was a private meeting with Carnap, Tarski, Neurath, Naess, Lutman-Kokoszynska, Hempel, and others where the proponents and opponents of Tarski's theory put forward their arguments. It was agreed (or, decreed by Carnap) that noone was to bring up the differences within the Circle regarding this issue in print.
Paolo's talk was followed by Johannes Hafner on the origins of model theory in Hilbert and Tarski. Johannes' main point was that whereas Tarski's notion of interpretation of an axiom system was a lot clearer about the syntax of the language (precise recursive definition of syntax in meta-language), Hilbert's notion of interpretation was a lot closer to the modern one--Tarski's notion of truth in the 1935 paper did not allow for varying domains. It wasn't until the 1950s in Tarski's and Vaught's work on model theory that the modern notion of truth in a structure emerged.
Submitted by Richard Zach on Wed, 06/07/2006 - 7:53pm
SciBlog, a blog project of a bunch of science writers in Vienna, goes live tomorrow with an event at Depot. If you're in Vienna, come on by.
Submitted by Richard Zach on Wed, 06/07/2006 - 5:28pm
Peter has posted a new version of the first 22 chapters of his Gödel Book.
Submitted by Richard Zach on Thu, 06/01/2006 - 9:39pm
The new issue of Philosophia Mathematica is devoted to Gödel. There are essays by Sol Feferman, Peter Koellner, Wilfried Sieg, Bill Tait, Rick Tieszen, and Mark van Atten, as well as a review of Torkel Franzén's Gödel's Theorem: An Incomplete Guide to its Use and Abuse.
Submitted by Richard Zach on Thu, 06/01/2006 - 5:11pm
After a week in Singapore and a week in Melbourne, I'm back in cold and rainy Vienna, nursing a cold and trying to finish two papers. Thanks to John and Belle, who I got to hang out with in Singapore, and to Allen, Conrad, Graham, Greg, Kate, Maren, Tama, and Zach for making it a thoroughly enjoyable visit to Melbourne.
Submitted by Richard Zach on Tue, 05/16/2006 - 11:34am
I'm in Singapore this week, giving a talk at ISMVL, and then visiting Greg in Melbourne next week. Regularly scheduled programming--such as it's been--will resume June 1.
Submitted by Richard Zach on Sat, 05/13/2006 - 3:04pm
A few more upcoming conferences marking Gödel's 100th birthday:
- The Annual Meeting of the ASL in Montreal next week will include a Special Gödel Symposium featuring Jeremy Avigad, Steve Awodey, Bill Tait, John Burgess, Akihiro Kanamori, and Sy Friedman.
- The Dutch Graduate School in Logic is putting on a Gödel Centenary Celebration in Utrecht, on May 26. The speakers are Mark van Atten, Dennis Dieks, Dick de Jongh, Juliette Kennedy, Benedikt Löwe, and Albert Visser.
- The Logic Colloquium in Nijmegen will include a 2-hour plenary discussion on the legacy of Kurt Gödel on August 2.
Submitted by Richard Zach on Fri, 05/12/2006 - 5:43pm
Submitted by Richard Zach on Fri, 05/05/2006 - 3:45pm
On Saturday, I unfortunately missed Ulrich Kohlenbach's talk, since the banquet the night before went a little long and I overslept. That was a pity, since I really like and admire his work. The second talk was by Harvey Friedman, "My 40 Years on His Shoulders". He as the title suggests, he gave a survey of his work on finding mathematically "natural" or "interesting" statements which are independent of strong theories. The three areas he focussed on was the theory of well quasi-orders (Kruskal's theorem, the graph minor theorem), Borel selection theory, and Boolean relation theory. If you've followed Harvey's posts on FOM, this was familiar territory. It was too bad that there wasn't more of a Friedman-MacIntyre discussion at the end. Then came the session on set theory: first, Paul Cohen reminisced about how he proved the independence of CH and his relationship to Gödel. He related how his interest in number theory as a graduate student at Chicago led him to think about developing a decision procedure for Diophantine equations. His colleagues there mentioned that what he tried to do onflicted with results of a certain Gödel--and this was confirmed by Kleene, when he gave a talk at Chicago during that time. This led Cohen to read Gödel's paper. He mentioned the story that circulates about how he [Cohen] allegedly asked Hartley Rogers in Princeton around 1958 what the hardest open problem in logic was, and that Rogers said it was the independence of CH--which Cohen then set to prove. Cohen said it rings a dim bell, but even if it hadn't happend the way it's been told, it would still continue to be told that way, because it's a good story. In any case, he attempted to read the Princeton monograph on the consistency of CH, but said he didn't understand it. He also said that he once asked Gödel if he had proved the independence of AC, and that Gödel had said, yes. Asked by what method, Gödel replied, "Well, it was somewhat similar to yours." At that time, Cohen reported, Gödel already seemed quite exhausted, and never wanted to talk about details of proofs. Cohen did want to debunk one claim made about him: that he at one point attempted to show that arithmetic was inconsistent (claimed, e.g., by Anil Nerode here)--he tried to find a decision procedure for Diophantine equations, which there isn't (see above). Dana Scott was up next. He gave an explanation for why Gödel's Princeton monograph is so hard to read: According to Kreisel, Gödel began the lectures upon which the monograph was based with a longish introduction where he explained the idea of the proof--but the notetaker though it was just chit chat and didn't write it down! Scott's talk was technical, on parametric sets and geometry, and I didn't quite follow it, I must admit. The third talk in the set theory session was Hugh Woodin on the large cardinal program. That was exciting and interesting, but I don't trust my notes enough to confidently report what he said. I think I've heard him give something like it at Berkeley already, so maybe there's a written version of it somewhere? In any case, here's a way to get a job in the Berkeley math department: Hugh bet that in the next 10,000 years no-one will prove ZFC + "there are infinitely many Woodin cardinals" inconsistent. If he loses, he will resign his job and insist that whever finds the contradiction be appointed in his place. In the afternoon, Avi Wigderson gave a talk on complexity, randomness, and game theory. It's up at his website. The last event of the meeting was Roger Penrose's public lecture at City Hall. The place was packed--probably 600 people or more. Since it was aimed at a general audience, there wasn't much detail. As far as I could tell, there wasn't that much new, either. Funnily enough, he seemed not to remember his own argument against strong AI using Gödel's theorems. Penrose's talk was followed by a screening of Jimmy Schimanovich and Peter Weibel's movie about Gödel's life and work, "Kurt Gödel--Ein mathematischer Mythos." The End.
Submitted by Richard Zach on Tue, 05/02/2006 - 6:20pm
Four interesting papers by Phillip Wadler:
- The unreasonable effectiveness of logic
- As Natural as 0,1,2
- From Frege to Gosling: 19'th century logic and 21'st century programming languages
- Proofs are Programs: 19th Century Logic and 21st Century Computing
available on his history of logic and programming languages page. (Hat tip: Lambda the Ultimate)
Submitted by Richard Zach on Sun, 04/30/2006 - 10:58pm
The first two people to email me their address get a postcard with a special Gödel Centennial stamp.
Submitted by Richard Zach on Sun, 04/30/2006 - 2:57pm
Day 2, Friday, was Gödel's birthday. I showed up for the panel discussion on unknowability, which wasn't particularly enlightening. Then Piergiorgio Odifreddi gave a very entertaining talk, in which he speculated on what philosophical writings may have served as inspiration for Gödel's results. He focussed on three figures: Aristotle, Kant, and Leibniz and drew some vague analogies between things Aristotle wrote in the Metaphysics and intuitionistic logic, between the antinomies of reason in Kant's first Critique and incompleteness, and Leibniz's calculus universalis and Gödel numbering. The latter was the most specific and interesting, I thought. Odifreddi reported that Sacks once told him that he heard Gödel say that he got the idea of arithmetization from Leibniz. Odifreddi went back to Leibniz' papers to see what was in there and said that the coding Leibniz used doesn't work -- the code of a string is just the product of the codes of the symbols in it. So this is an answer to the question prompted by Coffa I mentioned a while back, but at some point I should really figure out to what extent exactly Gödel coding was anticipated by Leibniz. Then Petr Hájek gave a survey of Gödel's ontological proof for the existence of God and the literature surrounding it. Hilary Putnam's talk was a follow-up to his paper "Reflexive Reflections" (Erkenntnis 22, 1985, 143-154). In that paper, he gave an argument that, if human language and scientific competence can be represented by a Turing machine, we can never know that this is so. It required an assumption, viz., that no mathematical falsehood can be justified by empirical evidence, and in this talk he attempted to get rid of that assumption.
I skipped the second panel discussion to get ready for the gala dinner that night in the Belvedere's Marble Hall. It was a very opulent affair. Here's a picture of the place setting, so you can see just how opulent:
The galleries were open, cocktails were served, Gary Kasparov spoke, we ate, then the Young Investigator Awards were presented:
After dessert, the string quartet performed the Barcarole from Offenbach's Tales of Hoffman, which was Gödel's favorite piece of music, and Paul Cohen gave an emotional closing speech which ended with everyone singing Happy Birthday.
Submitted by Richard Zach on Sat, 04/29/2006 - 12:23am
Submitted by Richard Zach on Fri, 04/28/2006 - 3:55pm
Here's where I channel Brian Leiter:
Distinguished logician and computer scientist Georg Gottlob, former chair of the Department of Information Systems at the University of Technology, Vienna, moves to Oxford University. This is a great loss for the TU Wien and the Viennese logic community. It is to be hoped that Gottlob will continue to be affiliated with the TU in some form or another.
(Georg was one of my teachers as an undergraduate -- why don't I hear about this sooner, I ask? Hello? Is noone in Vienna reading my blog?)
Submitted by Richard Zach on Fri, 04/28/2006 - 3:46pm