Full Idea
Some moods of the syllogism are fallacious, e.g. 'Darapti': 'All M is S, all M is P, therefore some S is P', which fails if there is no M.
Gist of Idea
The Darapti syllogism is fallacious: All M is S, all M is P, so some S is P' - but if there is no M?
Source
Bertrand Russell (Introduction to Mathematical Philosophy [1919], XV)
Book Reference
Russell,Bertrand: 'Introduction to Mathematical Philosophy' [George Allen and Unwin 1975], p.164
A Reaction
This critique rests on the fact that the existential quantifier entails some existence, but the universal quantifier does not.
Related Idea
Idea 13819 Aristotle's said some Fs are G or some Fs are not G, forgetting that there might be no Fs [Bostock on Aristotle]