Includes bibliographical references (p. 321-325) and index.

Review of classical propositional logic -- Review of classical first-order logic -- Alternative semantics for truth-values and truth-functions : numeric truth-values and abstract algebras -- Three-valued propositional logics : semantics -- Derivation systems for three-valued propositional logic -- Three-valued first-order logics : semantics -- Derivation systems for three-valued first-order logics -- Alternative semantics for three-valued logic -- The principle of charity reconsidered and a new problem of the fringe -- Fuzzy propositional logics : semantics -- Fuzzy algebras -- Derivation systems for fuzzy propositional logics -- Fuzzy first-order logics : semantics -- Derivation systems for fuzzy first-order logics -- Extensions of fuzziness -- Fuzzy membership functions.