[FOM] mathematics as formal
Alex Blum
blumal at mail.biu.ac.il
Mon Mar 31 02:46:36 EDT 2008
Steven Ericsson-Zenith wrote:
>On Mar 25, 2008, at 1:27 PM, rgheck wrote:
>
>
>>I thought logic was the study of such things as validity. It's no
>>convention that, if it's true that p and also true that q, then it's
>>true that p and q. It may be due to convention that the word "if"
>>means
>>if, etc. (Then again, it may not be.) But that's an entirely different
>>matter, and it is of no concern to logic.
>>
>>
>
>In my view the notion of validity applies only to convention. That is,
>the subject of validity is convention, and the question of whether the
>convention is absolute, true and complete is of interest but it is a
>separate matter.
>
>
It is clearly a matter of convenion what 'true' , 'and', and 'valid'
mean but surely given what they do mean, it is necessarily true that if
p and q are both true then p is true. Or, that if p and q have both been
proved then p has been proved. Just imagine the contrary in either
case. And if validity is a matter of convention what of inconsistency?
For if p is valid not-p is inconsistent.
Alex Blum
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