Third feature of scope-procedence in Grice's natural deduction system

-- by J. L. Speranza
for the Grice Club

This is stated on p. 123 of his "Vacuous Names". It relies on Mates's Elementary Logic that Grice is consulting (the first edition, 1965, since Grice is writing this in 1968 -- published in 1969).

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As Grice states this, this caveat for scope-procedence ensures that

"free variables [will] not occur in derivations."

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Also, that

"U. I. [will] involve, always, the replacement

of one or more subscripted occurrence of a bound variable

by one or more correspondingly subscripted

occurrences of an individual constant."

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