Subject: Re: Lewis Carroll
From: "William J. Rapaport" <rapaport@buffalo.edu>
Date: Sun, 31 Jan 2010 16:19:11 -0500 (EST)

Re: The paper by Wisdom that Prof. Scott recommended
(see
www.cse.buffalo.edu/~rapaport/584/S10/EMAIL/20100122-LewisCarroll-Validity.txt):

This is, indeed, an interesting paper. Wisdom agrees in part with my
interpretation of Carroll, namely, that rules of inference cannot be
premises, but he also thinks that Carroll's regress shows that a rule
of inference like Modus Ponens (From P and from P->Q, you may infer Q)
cannot be justified "syntactically" (i.e., by appeal to further
arguments) but must be justified "semantically" (i.e., in terms of
truth tables: A rule of inference is a valid argument pattern iff it is
truth-preserving).