When premises are true but the conclusion does not follow, the defect is in logical form.
Example:
Every human is an animal.
Every horse is an animal.
Therefore every horse is a human.
The premises are true. Yet animal is the predicate in both; sharing that wider genus does not make horses human. The argument violates the second figure's requirement that the premises differ in quality.
The rigorous diagnosis is not merely that the conclusion is false, but why entailment fails.
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Sophistical Syllogism: Illusory Premises, Deceptive Resemblances and Fallacies
When premises are true but the conclusion does not follow, the defect is in logical form.
Example:
Every human is an animal.
Every horse is an animal.
Therefore every horse is a human.
The premises are true. Yet animal is the predicate in both; sharing that wider genus does not make horses human. The argument violates the second figure's requirement that the premises differ in quality.
The rigorous diagnosis is not merely that the conclusion is false, but why entailment fails.