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Wednesday, April 11, 2012


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Man is a species (logical supposition)
Socrates is a man (real supposition)
Therefore, Socrates is a species.

Iirc & fwiw, medieval logicians would say the major is in logical supposition (has only mental existence) because the predicate cannot be passed on from the universal to the singular. The minor is in real supposition (has real existence) since the predicate can accept singulars. Hence, the syllogism is invalid because even though the middle-term ‘man’ is the same term it’s meaning (mode of existence, i.e. mental v. real) is different in the major and minor, resulting in the syllogism becoming a logical quadruped.


Perhaps we could construe species as a second-order property of man rather than as a concept included in the concept *man*.

Another possibility is to think of 'species' as an undetachable modifier predicate of the predicate 'man'. For instance, in 'x is a short basketball player', the predicate 'short' modifies 'basketball player' and therefore one cannot infer from the sentence 'x is a short basketball player' the sentence 'x is short'.

Both methods might avoid David's problem and preserve your intuition that the species inference is invalid.

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