## Repository Reorganization

As per issue #48, in order to keep the clutter in the main directory of the repository to a minimum, I’ve moved all the content directories containing texts to a subdirectory content/.  If you have a driver file that includes individual texts (part, chapter, or section) using \olimport, you will have to add “content/” to the optional directory argument.  If you use the starred version \olimport*, you shouldn’t have to do anything, as \olimport* now interprets paths relative to \olpath/content/. In other words, if your file contained the line

\olimport*[first-order-logic]{completeness}

you don’t have to do anything, but if you had, say,

\olimport[/home/zach/openlogic/first-order-logic]{completeness}

you’ll have to change that to

\olimport[/home/zach/openlogic/content/first-order-logic]{completeness}

If you have added your own files to the content directories or have started a new part (really? amazing! let us know!) then the first line of those new files will have to be changed by adding an extra ‘../‘ to the optional argument of the \documentclass command, e.g.,

\documentclass[../../../include/open-logic-section]{subfiles}

## Smith on the Open Logic Text

Peter Smith has written two blog posts (one, two) about the Open Logic Text.  He makes some very good points and raises some issues.  Since the OLP is under continuous development and still in the “alpha” stage, of course it won’t yet be a perfect replacement for a commercially published textbook without at least some work on behalf of an instructor who wants to use it.  The PDFs we produce so far, in particular, are not suitable for self-study.  Stay tuned for the “beta” release, when we hope to produce self-contained PDFs that can be used out-of-the-box.

Here are some of the specific criticisms, with links to the GitHub issues I’ve created for them. Feel free to comment on those or other issues or add your own!  And in the spirit of open source: feel free to propose some of these additional motivations and explanations!

• If you start with the part on “First-order Logic”, you will need to have previous experience with basic set theory for notation and mathematical background, and be familiar with proof methods such as induction.  The former is covered in the part on “Sets, Functions, and Relations”, the latter, a part on “Methods” is in the works (issue #60). The part on “First-order Logic” of course also needs an introduction (issue #69)!
• The sequent calculus material is sparse; we need more explanation of what proof systems do in general, how the proof systems relate to others a student might be familiar with from an intro course.  We now do have an alternate chapter on natural deduction, but that also needs to be related to the Fitch-style variants commonly used in intro textbooks (issue #61).
• We have a chapter on “Beyond First-order Logic”. As Smith says, it’s a “place-holder for later developments”, however, it can already serve the useful purpose of providing pointers to further topics in a course that can’t cover them in detail.  Of course, we do plan to cover them in detail eventually. I’ve added issues for modal, second-order, and intuitionistic logic as first priorities.  We already have some material for modal logic ready to be converted to OLP format.
• Smith describes Aldo’s treatment of interpolation and Lindström’s theorem as “crisply and clearly done.” However, the coverage of elementary model theory is spotty and much too fast (issue #65).
• The chapter on the lambda calculus has to be expanded to be useful (issue #66)
• Smith suggests to add “quite a lot more arm-waving motivation” to the arithmetization chapter (issue #67).

I do want to repeat here a comment I made in response to Smith’s summary remarks,

A general reflection on OLT. Having got to the end, it is clear that the different segments by different hands presuppose quite significantly different levels of sophistication from the reader. This makes me wonder a bit about the wisdom of presenting this resource as one long document rather than as a suite of separate modules. From the point of view of the rather daunted student, splitting things up would make it a lot clearer that you can and should  pick and choose various parts, depending on your background and interests. But also dividing things into modules might encourage the potential contributor.

## New Material on Natural Deduction

Thanks to Samara, the Open Logic Text now includes a chapter covering proofs in a natural deduction system.  The chapter, found in first-order-logic/natural-deduction, parallels the chapter on the sequent calculus closely.  Two new tags have been introduced, prfSC and prfND, both are on by default.  If on, the relevant chapter is included in the first-order logic part.  The completeness proof refers to both or either, depending on these tags.  I’ve also added a section in the incompleteness/arithmetization-syntax chapter which shows how to code and deal primitive recursively with natural deduction derivations.  The upshot is that you now have a choice of which proof system to use, simply by setting tags. Add \tagfalse{prfSC} to only have natural deduction, and \tagfalse{prfND} to only include the sequent calculus as before. Please file an issue on GitHub if anything got broken, or if you find mistakes in the new material.

## Aldo Antonelli, 1962-2015

We are shocked and saddened by the news that our friend, colleague, and collaborator Aldo Antonelli died this weekend.  He made significant contributions to philosophical logic, the philosophy of mathematics, and the history of analytic philosophy.  He was a gifted teacher, a mentor to many, and a wonderful person.  The Philosophy Department at UC Davis is setting up a scholarship in his memory.  We miss him.

## Alberta OER funding for the Open Logic Project

This spring, the Ministry of Advanced Education of Alberta launched a \$2m pilot project to encourage Alberta universities to develop, adapt, and use more open educational resources (OER). Of 15 funded projects, the Open Logic Project is one. AlbertaOER is running stories on their projects on their website, and one on the OLP is up already. Here it is in its entirety (Creative Commons licensing lets us do that!).

## Open Source: the Logical Choice for a Logic Textbook

#### The University of Calgary creates an open source logic textbook with international collaboration

Basic logic courses are an important part of several different programs spanning very different career paths, including computer science, linguistics, philosophy and mathematics. All of these subjects require that the learner have a grasp of the basic tenets of formal methods of logic, and the University of Calgary (U of C) offers three courses that can be applied to these varied backgrounds.

The commercial textbooks available for these courses are often very specific to certain backgrounds— some have more of a focus on mathematics, while others cater to those with a philosophical background. Richard Zach, Professor of Philosophy at the U of C, says that there are very few textbooks that serve a wide cross-section of audiences.

“Whenever you use one of those textbooks, the other people lose out—a math specific text might be full of theorems that make it difficult for someone with a philosophical background, for instance,” says Zach.

The solution is for several colleagues at international universities to pool course materials including lecture notes, handouts and other openly available content to create an Open Educational Resource (OER)—available free-of-charge to anyone online—that could be tailored to a specific audience. The U of C has been able to pursue the project thanks to funding from the U of C’s Faculty of Arts, and more recently through the Campus Alberta OER Initiative.

“That’s really what OERs are about. You provide teaching materials in such a way that the instructor or even the student can decide what material they want to cover, and in what order,” says Zach.

Developing the OER has been a collaborative project from the start though Zach is spearheading its organization—with several of Zach’s colleagues contributing, including Nicole Wyatt, the U of C’s head of the Department of Philosophy. Aldo Antonelli, a professor at the University of California, Davis, along with Andrew Arana of the University of Paris, Jeremy Avigad of Carnegie Mellon University, Gillian Russell from the University of North Carolina and Audrey Yap from the University of Victoria are also contributing. Three graduate students are also taking part in the project.

Zach hopes that the project will be ongoing. After the first draft’s completed at the end of December, he and his colleagues will continue adding and improving the book. Work on a project of such a scale with such a large number of people involved, and including complicated formulas, presents a challenge. Zach thinks LaTeX, a typesetting program that is often used to create scientific documents, is a good way to meet that challenge.

LaTeX allows users to insert whatever information is needed—whether it is mathematical or textual—in an easy manner, and produces PDF output that eventually can be printed as a professional-looking book or read on-screen.

Next, Zach had to determine what off-the-shelf software would be best for several people, located around the world, to use to collaborate on a textbook. He settled on the “revision control system” Git, which makes it easy for multiple users to make changes and collaborate on documents without any confusion.

Zach is excited to use a program that normally would be used for computer science, for the humanities. He even wrote a primer that explains how Git can be used by philosophers and other humanists. And he’s seen how well the program can work for other humanities projects since he has been collaborating on a large decade long project whereby the collective works of German-American philosopher, Rudolf Carnap, are being compiled and edited—this includes over 100 different texts and 14 volumes. The process has been very successful, and Zach believes other disciplines could benefit by using this program.

The website, openlogicproject.org, is already up and running with various documents available for download and information about the people behind the project. Zach is hoping the free resources will help ease the financial burden faced by some students while providing instructors with a logic textbook that can be customized to suit their classrooms.