Second of Grice's two goals in setting his natural deduction system

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

We see that the first goal (or 'objective') that Grice cares to list in a special section of Vacuous Names (section II: objectives) concerns one reading where ~ would not have maximal scope as Principia Mathematica advises it should have. Grice notes the caveat that his goal should also apply for formulae "which do not explicitly involve any negation-device").

The second goal is trickier. It amounts to allowing

'the unqualified validity ... of a step from'

'Pegasus does not fly'

'to the assertion (suitably interpreted) of'

'Something (viz. Pegasus) does not fly'.

This Grice calls S2, to oppose it to the two readings of S1 ('Pegasus does not fly').

----

S1
----
-.
.. S2


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