Re: SUO: Web site on concept maps
>
> >BTW, John, is the 'one-step' Existential Graph proof shown here
> >correct? If so, why does the first consequent have only a single
> >enclosing bubble, but the second one have two?
>
>That is a correct inference. In algebraic notation:
>
> (a & b) -> c
>
>Can be translated to:
>
> ~( a & b & ~( c ) )
>
>Add a double negation:
>
> ~( a & ~( ~( b & ~( c ) ) ) )
>
>Which can be translated to:
>
> a -> (b -> c)
Ah, I see. One can think of the outer 'double bubble' as belonging to
the outer implication, and the inner as belonging to the inner one.
Neat!
>But I wouldn't consider this the best illustration of Peirce's
>rules of inference. For a better discussion of EGs, I would
>recommend my commentary on Peirce's manuscript, MS 514:
>
> http://www.bestweb.net/~sowa/peirce/ms514.htm
Yes, so would I. Should be compulsory reading for logic students, this.
Pat
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