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Note: the 3rd edition site is still in "beta" with exercises being added daily. Please bear with us as we fill out the problem sets and make sure that all the links are working.
The Logic Machine, originally developed and hosted at Texas A&M University, provides interactive logic software used for teaching introductory formal logic. The Daemon Proof Checker checks proofs and can provide hints for students attempting to construct proofs in a natural deduction system for sentential (propositional) and first-order predicate (quantifier) logic. The Quizmaster provides a variety of exercises, from questions about basic concepts such as validity, to wff construction and translation, to proofs, truth tables, and countermodels. The system and exercises are based on Logic Primer (MIT Press, 2000) but the exercises are also suitable for use with other texts, such as E.J. Lemmon's Beginning Logic.