Providing free online linguistics, logic and foreign language lessons since 1998.

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    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's the pattern here? - thinking with abstractions | How do we go from concrete objects to general ideas? Why is this useful? Learn about identifying patterns, comparing common features and abstracting a new idea.
  • What else fits the pattern? - thinking with analogies | How does taking abstractions one step further let us learn and gain knowledge? Learn how we use analogies to extend patterns to new objects and new situations in language, logic, and creative and critical thinking.
  • What if the pattern's wrong? - thinking with errors | Abstracting patterns and applying them in new situations help us learn, but what happens when the pattern just doesn't work? How can errors help us learn?
  • 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.