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 a proof you wrote by hand. You confirm the reading before it is checked.
Blank template
A printable sheet to write proofs on. PDF.
Sentences and models
Truth tables
Every valuation of a propositional sentence, and its value under each.
DNF converter
Rewrite a propositional 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? The instructions cover how to write formulas and which proof rules are available.