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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