‘Tis the Season of Giving!

Do you have well-worked out teaching materials related to logic? We take donations of material that can be incorporated into the Open Logic Text.  Currently we’re interested in particular in material on modal logic and related areas (conditionals, intuitionistic logic), including history and applications. Other material on logic of interest to philosophers is of course also welcome. It can be anything from a one-off handout (which we’ll save until there’s a chapter it fits into) to a complete set of lecture notes. Remember that the audience is non-mathematicians, so very technical material may not find a place or might be substantially revised before being included. Of course, you must be willing to provide it under a Creative Commons Attribution license. If you have something that might be useful, just contact us.

[Photo by Howard Lake CC BY-SA]

Walter Dean (Warwick) Joins Editorial Board

We’re happy to announce that Walter Dean, Associate Professor of Philosophy at the University of Warwick, has joined the Open Logic Project’s editorial board.  Walter regularly teaches courses on the material currently covered in the text, as well as modal logic (inclusion of which is planned for next year) and provability logic and computational complexity theory.  He is planning to contribute to these topics in particular.

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.

Paid Undergraduate Internships with the Open Logic Project in Calgary, Summer 2016

We have openings, through a Canadian agency called MITACS, for advanced undergraduate students with a background in logic, philosophy, or computer science from Australia, Brazil, France, China, India, Mexico, Saudi Arabia, Tunisia, or Vietnam to come to Calgary for 12 weeks over the northern summer of 2016 (i.e. May-Aug). There are two openings, one to develop additional content for the Open Logic Text, and one for a programming-savvy student to add to and improve the open source collaborative authoring tools the OLP (and other projects) use. The internships are fully funded (travel, accommodation, living expenses); an information brochure is available on the site. The deadline to apply is September 24.

Unfortunately the way the site is set up we can’t link directly to the projects, but if interested folk go to the MITACS internship site and (somewhat counter-intuitively) choose “Start your application” they will be sent to an interface where they can choose the “projects” tab and search them (select “University of Calgary” as the university to narrow the search, and use “Logic ” (with trailing space) and “Open Source”, respectively, in the keyword field).  The two project descriptions follow.

Applications of Logic in Philosophy

The internship is located in the area of formal logic, especially as applied in philosophy and computer science. Propositional and predicate logic form a basis of theories of deduction, and formal models of various structures. Metalogic concerns the mathematical investigation of systems of logic, the relation between semantics and proof theory, and the theory of logical structures. Important limitative results delineate the expressive power of logical systems. These systems and their extensions (modal logic, intuitionistic logic) play an important role in some philosophical debates, especially in the philosophy of science and mathematics. Formal logic has many important applications in computer science and analytic philosophy, especially in philosophy of language, of mathematics, and of science. The Open Logic Project aims to develop and make available a textbook of topics in intermediate logic aimed at advanced undergraduate and graduate students in philosophy and computer science which develops these applications. They include background theory of use in philosophical applications such as modal logic, second-order logic, non-classical logic, model theory, and proof theory, as well as specific applications of these topics in philosophy. Examples of the latter are modal logics as models of knowledge, belief, or metaphysicsal reasoning; proof-theoretic semantics and Montague semantics in the philosophy of language; Craig’s axiomatization theorem or the Ramseyfication of a theory in the philosophy of science, Putnam’s model theoretic argument and Skolem’s theorem in meta-semantics; applications of many-valued logic in vagueness; intuitionism; interpretations of Gödel’s theorems in the philosophy of language. These are example topics; the intern will select a specific topic in consultation with the faculty supervisor.

The student will conduct independent research on one or more applications of logic to philosophy. This includes collecting primary research literature as well as other sources (lecture notes, presentations). The main result of the internship will be a contribution to the Open Logic Project in the form of a chapter or two on this application. This will require synthesizing the collected research and presenting it in a uniform, systematic format. The contribution will be prepared under supervision and will be reviewed and edited by other Open Logic Project collaborators.

The student should have a solid background in formal logic past a first course, e.g., know Gödel’s completeness theorem, the compactness and Löwenheim-Skolem theorem, or a background in non-classical logic. Interest and background in at least one of the potential areas of application is an asset (philosophy of mathematics, philosophy of science, philosophical logic). Knowledge of the LaTeX text preparation system is desirable but can be acquired during the internship.

Open Source Tools for Collaborative Authoring

Collaborative authoring of complex texts, such as entire books, in mathematics-heavy fields are a challenge. They require the use of de-facto standard scientific typesetting languages such as LaTeX. Complex collaborations are facilitated in software engineering projects using revision control systems such as Git. Using git for LaTeX project is a flexible, efficient, and cost-effective way to facilitate collaborative authoring of complex scientific texts such, and has been used for a number of large-scale projects such as the Open Logic Project or the Homotopy Type Theory project. During the internship, the student will work on software solutions to improve the effectiveness of this approach. Challenges faced include the lack of good tools to convert LaTeX code to semantic markup, to automatically provide text in multiple formats; contribution metrics for Git’s revision control system (e.g., compute contributor statistics based on words written instead of lines of code); and adapting software engineering tools for continuous integration to the collaborative authoring model.

The student intern will develop collaborative authoring tools on the basis of LaTeX and Git. This may include new package bindings for the LaTeXML conversion system; development of scripts to automate publication of LaTeX projects using Continuous Integration (CI) tools; and development of tools to facilitate using Git for text-based projects, such as a tool to generate contributor statistics based not on lines of code but on number of words.

Experience in using LaTeX, and elementary LaTeX programming, are required. To adapt conversion tools, coding experience in relevant programming languages is required, e.g., LaTeXML requires knowledge of Perl, and pandoc requires knowledge of Haskell. For adapting open source revision control systems, knowledge of Unix shell scripting, Git, CI tools, Make, and scripting languages are useful.

Open Logic Quick Start Guide

[Chad and Samara have documented the steps required to download and compile the Open Logic Text, and written a “quick start” guide for people who aren’t experienced with Git or may not even have LaTeX.  The most up-to-date version of this document can be found on the OLP wiki here.]

This page describes all the steps required to install and compile the Open Logic Text on your computer, including installation of LaTeX (the typesetting program OLT uses) and Git. Please see the pages on LaTeX and Git for more information on what those are if you don’t know already. You can avoid using Git by downloading OLT directly, but it makes it harder for you to keep up-to-date with changes to the text, and us to incorporate any contributions you make.

Installing LaTeX and Git

A LaTeX environment is necessary for both building a version of the Open Logic Book and contributing to the project. While it is possible to build the book without [Git], the project is currently hosted on Github, and you will need Git to contribute to the project.


The easiest way to get a working LaTeX environment on the majority of Linux systems is to install TeX Live through the package manager. The name of the package varies (texlive for Debian and Ubuntu with aptitude, texlive-most for Arch Linux with pacman, texlive and texlive-latex for OpenSUSE with libzypp). If TeX Live is not available through your distribution’s package manager or your distribution does not use a package manager (Gentoo), follow the instructions on the website to download and install TeX Live. To compile a .tex file into a .pdf file, use the pdflatex command at the command prompt.

Similarly, install git through your package manager. For an introduction to git specific to the Open Logic Project, see below.


Download the TeX Live installer for windows and run the executable. The installer will guide you through the installation process. Do not be alarmed if it takes a long time for the installer to download all the required packages. After installation is complete, you should be able to double click on latex source files to open them in the editor, from where you can click the green “play” button in the upper left hand corner of the interface to compile the document.

If you only want to build a custom version of the book, you don’t need to install Git on your system, it is enough to click the “Download ZIP” button on the right hand side of the Github interface on the project page, and extract the contents to a convenient location. If you want to contribute to the project, the easiest way is probably to install Github for Windows.


Install MacTeX to obtain a LaTeX environment. If you’re comfortable with the command line, install Git. If you choose the command line most of the instructions and advice for Linux systems will apply to you also. If you prefer a GUI, install Github for Mac. Ideally you will install both, allowing you to try typing the git commands as they appear for Linux users, with the GUI as a fallback if something isn’t working for you.

Git Primer: “Fork” and Other Verbs

Git is the distributed version control system used by the Open Logic Project. It allows multiple people to work on the project at the same time, and makes creating your own version of the project and incorporating your changes into the main project easy. A collection of files managed with Git is called a repository. The Open Logic Project repository is hosted on Github, a hosting service for Git repositories with a nice web browser interface. Git is a somewhat complicated system, and can be intimidating for new users. The aim of this section is to help you become comfortable with what Git is and get you started using it.

To contribute to the Open Logic Book, you will probably want to register an account with Github. While this is not necessary if you are looking only to use the text, and not strictly necessary if you would like to contribute to the project, it will make both of these things far easier. During the account creation process you may be asked to choose a payment plan. The free one will suffice.

Once you have a Github account, the first thing you should do is create a copy of the the OpenLogic repository tied to your account. To do this, log in to your Github account, and click the “Fork” button on the page for the repository (In the upper right hand corner of the web interface). A copy of the repository should now be displayed on your Github profile page at https://github.com/<yourusername>. Any changes you make to this repository will not be reflected in the main OpenLogic repository. You can request that your changes be added to the main repository by issuing a “pull request”, covered here.

Now that you have your own copy of the project files on Github, the next step is to get those files on your computer. If you’re using git from the command line, navigate to the directory you want the files to be in and enter

git clone https://github.com/<yourusername>/OpenLogic

at the command prompt.

If you’re using the Github GUI interface for Windows (or the similar application for OSX), you need to link your Github account to the instance of the software on your computer. If you are not prompted to do this when you first start it up, you can do it by clicking the gear icon in the upper right corner of the main window of the application. Once you have linked your account, you will be able to clone your fork of the OpenLogic repository by clicking the plus sign icon in the upper left corner of the main window, and selecting “clone”, and finally selecting your fork of the repository. You will be prompted to enter a save location, and it doesn’t matter what this is as long as you remember it. Once you have done this, the copy of the files on your computer will behave much the same as for Linux and OSX users, with the difference that you will have to use the Github for Windows application instead of the command line to do the things described below. The Github for Windows application comes with a low-powered “shell” that will act a bit like a Unix command prompt, and makes it easier to perform more complex operations should the need arise. Please consult the documentation for more information on the Github for Windows application.

There are three sorts of basic changes you can make to the repository, adding new files, changing old files, and removing old files. To add a new file called file.ext to the repository, move the file to the OpenLogic directory on your computer and type git add file.ext. This tells git to keep track of file.ext. To make changes to a file that git is already keeping track of (such as the files that were in the repository when you cloned it), simply edit the file. To remove a file called file.ext from the repository, type git rm file.ext at the command prompt. This not only tells git to stop tracking the file, but deletes it. To record changes you have made, type git commit -m "summary of changes" at the command prompt. If you don’t want to record your changes, you can type git reset to restore the repository to the state it was in immediately after the last commit. Finally, to synchronize the changes you have made with the version of the repository on Github, type git push at the command prompt (after committing your changes).

If you are using Github for Windows it easy to commit and push changes. Once you have edited a document that Git is currently tracking, or added a new document to the OpenLogic directory on your computer, it will pop up in Github for Windows as an uncommitted change. You can select/deselect files to commit at this point. You must write a summary of the commit, and are given the option to add a short description. Once you have done so, hit the commit button. At this point, the changes you have made will not be reflected in the version of the repository on Github. You should see that the sync button at the top of the application now has a number beside it, reflecting the commits that have yet to be pushed to Github. When you are ready to push your changes, click the sync button.

To request that your changes be reflected in the main Open Logic Project repository, submit a pull request.

The pull request can be done directly from Github for Windows, but the application does not have a compare and review feature. If you’d like to do a comparison of the changes you’ve made before submitting a pull request, follow the instructions linked to above. If you’d like to do the pull request directly from Github for windows, you can do so by clicking the pull request button to the left of the sync button. The program will show you which branch the changes are being taken from, and where you are sending the updates to. The default options for the pull request should be correct, but you may want to double check that the pull request is being sent to the correct place (in most cases, this should be from your master branch into OpenLogicProject/master). You’ll have to enter a title, and if you’d like, a description. Then click “Send pull request”, and you’re done!

If you want to update your copy of the repository to include changes in the main repository that have happened since you made the copy, read this. Alternatively, and if the “upstream” changes can be synced into your fork without manual intervention, you can use the Github web interface to sync changes from the main repository into your fork. To do this, proceed as if you were sending a pull request, but switch the “base fork” and “head fork”. (The base for should be “yourid/OpenLogic”, the head fork “OpenLogicProject/OpenLogic”; and in each case the branch should be “master”). Github will tell you if an automatic merge is possible. If it is, you will have sent yourself a pull request that you can merge.

Building the Open Logic Book

Once you have a working LaTeX installation and a copy of the Github repository on your computer, you can compile a custom edition of the Open Logic Book. To build the complete book (all chapters included), compile the open-logic-complete.tex file. The open-logic-debug.tex file also produces a complete PDF, but with extra debugging information that helps to keep track of labels of theorems and the like, and which files which parts of the final PDF come from.

The files in the main directory should not be changed. To make a customized version of the book, instead go to the courses directory, and copy the sample subdirectory. Your copy should contain two files, open-logic-sample.tex and open-logic-sample-config.sty. You may rename these files, e.g., to myversion.tex, myversion-config.sty (where “myversion” can be any string). You can make any changes to the layout, fonts, page style, etc., in myversion.tex you like. You can also rearrange the order of the parts and chapters or leave out parts you do not want included. For instance, to exclude the part on computability theory, change the line




in myversion.tex.

To change the OLT-specific configurations, e.g., how formulas are printed or whether formulas are called “formulas”, “formulae”, or “wffs”, open myversion-config.sty in a text editor. The configuration options are explained in open-logic-config.sty in the main directory. Copy any configuration option you would like to change to myversion-config.sty and make your changes.

Finally, generate a PDF of your custom textbook by compiling the myversion.tex file with pdflatex.

You can keep different versions of the text in different directories by following the same steps as before.

Open Logic Project Special LaTeX Syntax

The Open Logic Book is configurable, you can choose which word you want the book to use for a number of technical terms, and more! To achieve this we preface configurable elements with a special syntax in the .tex files of book chapters. This makes writing chapters for the text a bit more complicated that it would have otherwise been, but not by too much. In addition to this section, you will have to read the open-logic-config.tex file in the top level of the OpenLogic repository, which contains a complete listing and explanation of the syntax.

The pattern common to all of the special syntax is that instead of using the standard LaTeX macros for a particular symbol, you use a specific Open Logic Project macro, e.g., \lif for a conditional symbol instead of \rightarrow. When the document is compiled, the special macro is replaced with text according to the configuration of that instance of the book. Sometimes the OLP uses the standard macro, e.g., \land. For example, one of the configuration options allows you to choose between the Greek and Latin alphabets for the symbols used to represent formula metavariables. For this to work, when you write material for the book you must use the syntax !A, !B, and so on for formula metavariables. Other configurable things include the symbols used for various sets of numbers (natural, real, integer, and so on), logical connectives (including quantifiers), and the syntax for relations like provability and entailment.

“Tokens” are slightly different than the rest of the configurable syntax. The idea is that in addition to using different symbols for the same thing across book instances, we might also want to use different words. This is done by treating some words, like “formula” and “variable” differently, as Tokens. When you use a tokenized word in material for the Open Logic book, instead of typing it, you have to enclose it in braces and place two exclamation points in front of it. That is, instead of typing




instead. To typeset the (configurable) plural form of a token word, type


and to typeset the token word with a (configurable) article, type


The complete list of tokenized words and instructions for customizing tokens can be found in the configuration file open-logic-config.tex

Free Logic Textbooks

The Open Logic Text may be one of only two open source logic texts, but there are other open, and even more non-open but still freely available textbooks of various levels.  We’re keeping track of them on the Open Logic wiki:

Other Logic Textbooks

The most popular intro level text is P. D. Magnusforall x, which deserves special mention since it is, like the OLT, open source. The LaTeX code is available, which means there’s not just a PDF you can give your students, but you can make a PDF to your own specifications, with your own additions or changes.  Other free texts are available only as PDFs or online in HTML format, and most of them are not provided under a license which allows you to distribute them, let alone make changes to them.

If you are the author of teaching resources — from handouts to complete textbooks — and you want others to be able to make use of them, please (a) provide the source code and (b) make them available under an open license, such as CC-BY.

Made the Daily Nous!

The Daily Nous covered the Open Logic Project today, suggested an alternative logo that might fit better with the anarchical open-source spirit: