[hist-analytic] Discussion of Aune's ETK, Chapter Two: Modus Ponens/Tollens

Danny Frederick danny.frederick at btinternet.com
Fri Oct 30 09:26:04 EDT 2009


Hi Steve,

 

My concern was simply to rebut the claim that the argument is a
counter-instance to modus tollens. For that claim to be true, the argument
would have to be invalid, since it evidently (to me) is of the modus tollens
form. But I showed that the argument is valid, and thus not a
counter-instance to modus tollens.

 

When I use predicate logic to exhibit the formal inconsistency of the
premises, I use a variable 'x' that ranges over events (hence the reference
to Davidson). Thus,

 

(Ex)(Rx & Hx & Yx)

 

means: there is an event which is a raining, a hard raining and happened
yesterday.

 

I am making no comment on the success or otherwise of Davidson's analysis of
event-statements as a semantic analysis of English. I utilise it simply as a
way of putting the puzzling argument into logical form. For what it is
worth, I do not believe that the structure of English is exhibited by
first-order predicate logic.

 

I don't deny that it is possible to interpret the 'if' in the first premise
in other ways. Plainly, that seems natural to you; for what it is worth (not
much) it seems unnatural to me. Perhaps this is just a slight difference
between our idiolects or, perhaps more likely, a difference in assumptions
about the context of utterance.

 

Do note that I am saying that the argument is VALID. That is why it is not a
counter-instance to modus tollens (which it exemplifies).

 

I think Bruce's question about modus ponens is about the meaning of 'if' and
the logician's hook.

 

Cheers.

 

Danny

 



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