The source example:
«كل حيوان إنسان»
Every animal is human.
Its correct contradictory:
«بعض الحيوان ليس بإنسان»
Some animal is not human.
If all animals are human, there can be no counterexample, so the particular negative is false. If the universal is false, at least one counterexample exists, making the particular negative true.
“No human is an animal” is not its exact contradictory; it is a universal negative, a stronger claim than what is required for denial of “every”.
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Contradiction: Definition, Conditions and Application to Propositions
The source example:
«كل حيوان إنسان»
Every animal is human.
Its correct contradictory:
«بعض الحيوان ليس بإنسان»
Some animal is not human.
If all animals are human, there can be no counterexample, so the particular negative is false. If the universal is false, at least one counterexample exists, making the particular negative true.
“No human is an animal” is not its exact contradictory; it is a universal negative, a stronger claim than what is required for denial of “every”.