LessonsThe Fourth Figure: Productive Conditions, Moods and ProofsQuiz

With two affirmative premises, the proof establishes a positive overlap: “Some teachers are reciters” together with “All reciters are human” gives a particular affirmative conclusion.

With one negative premise, the proof may instead establish exclusion: “No poet is a reciter” with “Some reciters are teachers” entails “Some teachers are not poets.”

This is a distinction of quality. Whether the result is universal or particular is a separate issue of quantity and must follow from what the premises cover.

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Why conclusion quality follows the exclusion

The Fourth Figure: Productive Conditions, Moods and Proofs

With two affirmative premises, the proof establishes a positive overlap: “Some teachers are reciters” together with “All reciters are human” gives a particular affirmative conclusion.

With one negative premise, the proof may instead establish exclusion: “No poet is a reciter” with “Some reciters are teachers” entails “Some teachers are not poets.”

This is a distinction of quality. Whether the result is universal or particular is a separate issue of quantity and must follow from what the premises cover.