[lit-ideas] Re: The Educational Value of Slips of the Whatever
- From: Robert Paul <rpaul@xxxxxxxx>
- To: lit-ideas@xxxxxxxxxxxxx
- Date: Mon, 28 Sep 2009 19:40:27 -0700
Richard wrote
I pray, and I think we should all so pray that Donal is indeed
"mistaken" that "any assertion, including those as to the validity
of deductive inferences, is possibly or potentially mistaken." This
is an extremely radical position, fit, metaphorically speaking, to
put quicksand under the basis of all our mutual understanding,
unless Donal is saying, in effect, "not to worry--even if a given
assertion as to the validity of deductive inferences is mistaken,
that would not preclude the validity of deductive inferences so
asserted." I'm afraid it is significant, that is, it is
"educational" that Donal is having semantic issues with the word
"validity." A sound argument is not a valid argument. The avoidance
of contradictions in one's arguments is one step in the direction of
a sound argument, but no guarantee of its validity.
This last point seems right. In 'Roses are red, violets are blue;
therefore, Alexander was Aristotle's pupil,' there are no
contradictions, but the argument is invalid, for the conclusion can be
false even if the 'premises' are true. It doesn't contradict the
premises but neither does it follow from them.
I'm dubious about Richard's earlier point, viz., that a sound argument
is not a valid argument, for, if 'sound,' and 'valid' are used as
logicians usually do--that is, as technical terms--every sound
argument is valid by definition, even though the converse isn't true.
A valid argument is so in virtue of its form alone; a sound argument
is a valid argument whose premises are all true.
'Valid,' and 'sound,' may have all sorts of other uses in ordinary
speech, but these are the ones of interest to philosophers, even
'ordinary language philosophers,' if any still exist.
Robert Paul
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