Re: In need of the all-out revision of symbolic logic

On Apr 29, 4:59 am, Eukie_M_SHIRAISHI <ms.eu...@xxxxxxxxx> wrote:
In the Fregean Theory of Logic (the standard theory of logic in the
20th century),
“p implies q” has had been defined to mean “not-p or q”.

Here let P be “A lion is a mammal” and Q be “A lion and a whale are
both mammals”
It is clear that Q implies P but P does not imply Q.
Hence “P implies Q” is a falsity.
On the other hand, “not-P or Q” is a truth.
Therefore, it is a mistake to define “p implies q” to mean “not-p or
q”.

Sorry, but I don't see why is “not-P or Q” true. I mean, what if a
lion and a whale are both not mammals?

It is not the situation in real world, but when you compare logic
statements, only the possible truth vlues of p and q metter. In our
case, they both aree true, so the truth values of both “p implies q”
and “not-p or q” are T.

I'm not a logician, so I'd be dilighted to see an explanation on the
subject...
.

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