<philosophy of science, logic> the reciprocal relationship between two categorical propositions of the same form such that the subject term of each is the complement of the predicate term of the other. Contraposition is a valid immediate inference for both A and O propositions. Thus, for example: "All voters are citizens and All non-citizens are non-voters", "Some ants are not biters and Some non-biters are not non-ants" are legitimate cases of contraposition.
[A Dictionary of Philosophical Terms and Names]
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