Interested in completely free, browser-based, instructional logic software?

Brian Rabern spent a decade at the University of Edinburgh working in logic, formal semantics, and other areas of philosophy before moving into the tech world.

Unable to find logic software that met his needs, he and a former student created Elogic. Initially developed for his courses, it has since been used at several universities.

He is now making the software freely available to anyone who wants to use it. He describes it below.

Elogic: Free Web-Based Logic Software
by Brian Rabern

I taught introductory logic to large classes (400-500 students) for over a decade. The desktop software I inherited worked, but supporting it was a headache: install conflicts, only supported on certain devices, students fighting IT on shared machines. In 2014 a student in my class and I started building a web-based replacement. That became Elogic.

It’s a browser-based environment for logic exercises with immediate, automated feedback. There’s nothing to install, and it works on anything with a browser. The guiding design idea was to make something genuinely intuitive for first-year philosophy students, the students who are there for epistemology or ethics or Nietzsche and encountering formal notation for the first time. The interface should get out of the way, not add a learning curve on top of the logic itself.

1. What it does

Four core exercise types:

• Symbolizations. Translate English into propositional or first-order logic. Answers are checked for logical equivalence (using an SMT solver), not exact match to one official answer. Feedback distinguishes syntax errors from meaning errors.
• Derivations. Natural deduction proofs in a Fitch-style layout. Guided feedback on rule use, scope, and variable capture. Supports rule-locking: derived rules are withheld until prerequisite theorems are proved.
• Truth tables. Row-by-row feedback on missing or wrong values.
• Countermodels. Build an interpretation that makes the premises true and the conclusion false. Checked automatically via SMT solver.

2. Scope and limitations

Elogic is opinionated. The natural deduction system is Kalish-Montague style in Fitch format, aligned specifically with Parsons’s An Exposition of Symbolic Logic. The notation, rule names, and proof conventions match that presentation. This is designed for courses using that text or something close to it, not as a general-purpose tool configurable for arbitrary proof systems or notations. (This mostly applies to the derivation exercises, not so much the symbolizations, truth tables, etc.)

If you need something more flexible, various notations, various proof systems, Carnap.io is the project to look at. Elogic does one thing and tries to do it well.

3. It’s free

Elogic used to be behind course join codes with licensing fees, to cover cloud hosting. That’s over. It’s now free educational software, no sign-up required. Three ways in:

• Try immediately: click “Try without an account.” No sign-up, nothing. Progress saves in your browser.
• Sign up free: create an account and your work syncs across devices.
• Run a course: instructors get an admin dashboard with student join codes, a roster, per-assignment progress stats, grade exports, and the ability to view any student’s work. Also free.

4. Getting started

Go to elogic.land, click “Try without an account,” pick a problem, work it, hit Check. See the help guide for how to use it: elogic.land/help

If you’re an instructor interested in using it for a class, email me and I’ll set you up with a course.

This was built because I needed it and couldn’t find it. The intention is for Elogic to stay free permanently. There is no secret upsell, no premium tier. I just have a thing that I and others have found useful for teaching logic, and it seemed wrong not to share it. So I’ve opened it up. Feedback (to [email protected]) is always welcome: what works, what doesn’t, what’s confusing.