Okay but I still don't see how the law of the excluded middle says that "a and not a" is always valid.
Grandparent said that the law doesn't say that "a and not a" is always INvalid. (The law also doesn't say that "a and not a" is sometimes valid. It makes no comment at all, but only claims that "a or not a" is always valid. According to the grandparent. Now I need to lie down for a bit....)
Yes, this.
The point was that you can reject the law of the excluded middle without getting into the absurdity that would result from accepting "a and not a".
Unknown questions are A and not A.
There’s interesting alternative logic systems that try to tackle this.
We get into interesting territory when using English and then “is” as a statement. Most English is assumed to have a certain value because of to be.
English is almost inherently flawed with logic bugs and assumptions.
E-Prime may help with this.
1. https://en.wikipedia.org/wiki/Catu%E1%B9%A3ko%E1%B9%ADi
2. https://en.wikipedia.org/wiki/Jaina_seven-valued_logic
3. https://en.wikipedia.org/wiki/Infinite-valued_logic