PHIL-1003 Lecture Notes - Lecture 12: Obversion, Contraposition, Immediate Inference
23 Aug 2018
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Opposition: the logical relations that exist between any two categorical propositions that defers in quantity, quality, or in other respects. Cannot both be true, cannot both be false. Same s and p term but defers in both quantity and quality. Cannot both be true, but can both be false. Universal propositions having the same s and p terms but differing in quality (one affirming, the other denying) Can be both true, cannot be both false. Particular propositions having the same subject and predicate terms but differing in quality (one affirming, the other denying) Corresponding propositions: same s and p, agree in quality, but differs in quantity. Subalternation: the opposition between a universal proposition and a corresponding particular proposition. The superaltern implies the truth of the subaltern. An inference that is drawn directly from one premise without the mediation of any other premise. Various kinds of immediate inferences may be distinguished, traditionally including conversion, obversion , and contraposition .
