Simple conversion exchanges subject and predicate under rules that preserve truth and quality. The first two second-figure moods can be related to first-figure reasoning by this method.
Reductio temporarily assumes the contradictory of the conclusion and shows that it cannot coexist with the premises. This need not proceed by directly rearranging the premises.
Both establish the same point—necessary consequence—but the inferential routes differ.
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The Second Figure: Conditions of Validity and Four Productive Moods
Simple conversion exchanges subject and predicate under rules that preserve truth and quality. The first two second-figure moods can be related to first-figure reasoning by this method.
Reductio temporarily assumes the contradictory of the conclusion and shows that it cannot coexist with the premises. This need not proceed by directly rearranging the premises.
Both establish the same point—necessary consequence—but the inferential routes differ.