Symbolic Logic Tools

Companion tools for How Logic Works. Check a natural-deduction proof, evaluate a sentence in a finite structure, or build a truth table.

Proofs

Proof checker — type a proof and have every line checked against the rules

Check a photo of a proof — photograph one you wrote by hand; you confirm the reading before it is checked

Blank template — a printable sheet to write proofs on

Sentences and models

Truth tables — every valuation of a propositional sentence, and its value under each

DNF converter — rewrite a sentence in disjunctive normal form

Model checker — build a finite structure and evaluate a closed sentence in it

Graphical model builder — draw a structure and read off what holds in it

New here?

Instructions — how to write formulas, and which proof rules are available

For instructors

Dependency and Scope — on translating between Lemmon and Fitch proofs: why one direction is easy, why the other is not, and what the difference says about the two notations. PDF, draft

Source — Haskell, open, with the regression corpus the paper reports on