Meta stuff

General, easy-to-follow perspectives on logic.

What is logic? | Get a taste of the basics of logic with Socrates' questioning and Aristotle's syllogisms. Explore the difference between form and content, variables and operators, valid vs. true conclusions, and reasoning vs. reasoning well as you think about thinking.
What is Meaning? Semantics, Semiotics, Logic & the Meaning of Words. | How do words and other signs mean something? How is meaning studied? Get a brief idea of the various approaches to meaning in language.

Core lessons

These free online lessons include videos, text & activities.

Logic & Language | Learn to translate ordinary language into precise logical statements. Use logic as a tool for analyzing human language. Covers constants, variables, subjects, predicates, quantifiers, connectives/operators and sets.
Logic of Arguments | Learn to evaluate arguments using logic. Covers form & content, premises & conclusions, truth & validity, deduction versus induction, and formal & informal logical fallacies.
Truth Tables | Expand your understanding of truth values in logic through truth tables. Compare binary (true/false) truth values of propositions and operators, including the negation NOT, conjunction AND, disjunction OR, implication/conditional IF...THEN and the biconditional IF AND ONLY IF. The analogy of a lightbulb and lightswitch are used to illustrate each operator.
Inverse, Converse & Contrapositive | See how to switch around statements in propositional logic. Use the example 'if it's a bike, it has 2 wheels' to explore inverses, converses and contrapositives. Abstract your understanding to any propositions A and B, where A implies B.