∃x4~2F1x3 vs ∃x4~3F1x2>

by J. L. Speranza
for the Grice Club.

Similarly, later on that page 122, Grice opposes these two formulae:

∃x₄~₂F₁x₃


∃x₄~₃F₁x₂


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The difference:


The former will, in System [G] be "derivable from

~₂F₁a₃, but not from

~₃F₁a₃; [the latter]

will be derivable directly (by E[xistential

G[eneralisation]) only from ~₃F₁a₂."


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