LessonsQiyās al-Khalf: Compound Reductio, Impossibility and Proof of the ClaimQuiz

Qiyās al-khalf is a compound proof: assume the contradictory of a claim, demonstrate that it entails an impossibility, reject the contradictory, and establish the claim.

For soundness, the opposing assumption must be the actual contradictory, the entailment must be valid, the consequent genuinely impossible, and the second inference must correctly deny the consequent.

The source uses “Every human is an animal” and rejects the corresponding particular negative. The following section begins a new discussion of the form and matter of syllogism.

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Qiyās al-Khalf: Compound Reductio, Impossibility and Proof of the Claim

Qiyās al-khalf is a compound proof: assume the contradictory of a claim, demonstrate that it entails an impossibility, reject the contradictory, and establish the claim.

For soundness, the opposing assumption must be the actual contradictory, the entailment must be valid, the consequent genuinely impossible, and the second inference must correctly deny the consequent.

The source uses “Every human is an animal” and rejects the corresponding particular negative. The following section begins a new discussion of the form and matter of syllogism.