Consider: 'No reptiles are warm-blooded. Some snakes are reptiles. Therefore, no snakes are warm-blooded.' Which is the BEST assessment?
AThe argument is valid because the conclusion follows from the premises
BThe argument is INVALID — from 'some' in P2 we cannot deduce 'no' (a universal negative) about snakes; the conclusion overreaches
CThe argument is sound
DThe argument is a valid modus ponens
Answer & Solution
Correct answer: B. The argument is INVALID — from 'some' in P2 we cannot deduce 'no' (a universal negative) about snakes; the conclusion overreaches
Categorical logic: P1 'No R are W' + P2 'Some S are R' yields only 'Some S are not W' (those S that are R are not W). Concluding 'NO snakes are warm-blooded' is an illicit move from particular to universal.
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