Contraposition (traditional logic)

In traditional logic, contraposition is a form of immediate inference in which from a given proposition another is inferred having for its subject the contradictory of the original predicate, and in some cases involving a change of quality (affirmation or negation).Brody, Bobuch A. "Glossary of Logical Terms". Encyclopedia of Philosophy. Vol. 5-6, p. 61. Macmillan, 1973. Also, Stebbing, L. Susan. A Modern Introduction to Logic. Seventh edition, p.65-66. Harper, 1961, and Irving Copi's Introduction to Logic, p. 141, Macmillan, 1953. All sources give virtually identical definitions. For its symbolic expression in modern logic see the rule of transposition. Contraposition also has distinctive applications in its philosophical application distinct from the other traditional inference processes of conversion and obversion where equivocation varies with different proposition types.

Traditional logic

In traditional logic the process of contraposition is a schema composed of several steps of inference involving categorical propositions and classes.Irving Copi's Introduction to Logic, pp. 123-157, Macmillan, 1953. A categorical proposition contains a subject and predicate where the existential impact of the copula implies the proposition as referring to a class with at least one member, in contrast to the conditional form of hypothetical or materially implicative propositions, which are compounds of other propositions,...
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