Logic / Unit 6 Logic 263 short lesson, about 20 seconds
The Pairing Rule
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The idea
Universal quantifiers take ⊃; existential quantifiers take ·.
In practice
(x)(Sx · Px) says everything is both S and P — far too strong. (∃x)(Sx ⊃ Px) is true if anything at all fails to be S — far too weak.
Where people slip
Both mispairings produce well-formed nonsense: grammatical, meaningful, and never what you meant.
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