## Guess the Logician!

We’ve been working with Calgary graphic designer and illustrator Matt Leadbeater on a series of stylized portraits of logicians. They will be licensed under a Creative Commons Attribution-NonCommercial license (free to use for teaching, but you can’t sell coffee mugs with them on it), and they will be included in the Open Logic Text repository.

Before we make them all available, we’re playing a little game. They’ll be posted without names on Facebook, Twitter, and Google+, and we’ll let you guess who they are!

Props to the Alberta OER initiative for making this happen by providing funding. Making open textbooks visually attractive is an important but overlooked aspect of the OER production process.

## Logicians’ Biographies

Thanks mainly to Samara‘s efforts, the Open Logic Project has begun to include short biographies of logicians in a new History part (Source on GitHhub, PDF).  So far we have Cantor, Church, Gentzen, Gödel, Noether, Russell, Tarski, Turing, and Zermelo.  We’ve made an effort to appeal to our target audience — undergrad students from a variety of backgrounds — and kept them short and as non-boring as possible.  References are included not just to academic biographies, but also to YouTube videos and podcasts.  As always, feedback is more than welcome, and we take requests for additions!

In order to enable these biographies to contain references, all driver LaTeX files now automatically generate and include a bibliography.  The bibliographies so far are the only texts that contain references (in Natbib author-year format), but they can now be included in other texts as well. Two environments, ‘history’ and ‘reading’ for Historical Remarks and Further Reading sections are now available (defined in open-logic-envs.sty) and material using these will be added to the main text as time goes on. We’re also very close to including portraits!  To keep the main repository to a reasonable size, these will be provided in a separate GitHub repository.

[Photo credits: Alan Turing / National Portrait Gallery CC-BY-NC-ND; Georg Cantor / University of Halle Archives; Kurt Gödel / Institute for Advanced Study Archives; Emmy Noether / Göttingen University Library]

## New in the Open Logic Project: Turing Machines

We’ve had a very rudimentary chapter on Turing machines in the OLP for a while.  Samara and I have been working on expanding this over the last few months, using Nicole’s notes and writing some stuff from scratch. It is now is mature enough, I think, that it can be included. So I have merged the turing-machines branch into master.

A decisions of which variant of Turing machines to use had to be made. We opted for a version that allows the machine to write and move at the same time, since most of the online emulators work that way. We also decided to let the tape be infinite in one direction only. This makes the proof of undecidability of logic, which requires describing Turing machine configurations, a lot simpler.

It still needs work, of course, like everything else. More examples, more problems, a more in-depth discussion of the Church-Turing thesis, proofs of equivalence of different Turing machine variants, for instance. To tie it to the other computability material, I’d like to show that recursive functions are Turing computable. It would also be great to have some discussion of computational complexity and non-deterministic computation; Dean indicated that he might work in that direction.

In the meantime, enjoy, and please give feedback!