LessonsContraposition: Classical Rules, Validity and the Later ConventionQuiz

«هو جعل نقيض الجزء الأول من القضية ثانيا، ونقيض الجزء الثاني أولا مع بقاء الصدق والكيف»
Make the complement of the first part the second, and the complement of the second part the first, while preserving truth and quality.

This is the earlier logicians' formulation. If the original subject is “human” and predicate “animal,” the resulting subject is “nonanimal” and predicate “nonhuman.”

Preserving truth means truth of the premise supports truth of the result. Preserving quality means that an affirmative stays affirmative and a negative stays negative.

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The earlier definition of contraposition

Contraposition: Classical Rules, Validity and the Later Convention

«هو جعل نقيض الجزء الأول من القضية ثانيا، ونقيض الجزء الثاني أولا مع بقاء الصدق والكيف»
Make the complement of the first part the second, and the complement of the second part the first, while preserving truth and quality.

This is the earlier logicians' formulation. If the original subject is “human” and predicate “animal,” the resulting subject is “nonanimal” and predicate “nonhuman.”

Preserving truth means truth of the premise supports truth of the result. Preserving quality means that an affirmative stays affirmative and a negative stays negative.