PeteOlcott wrote: ↑Sun Mar 24, 2019 4:02 pm
My last reply seems to have gotten lost. I also agree that the principle of explosion is semantically unsound.
I do not want to digress into talking about this until all of my current points are fully addressed.
Relevance logic seems to address the principle of explosion quite well.
My main point is that it impossible for truth and provability to ever diverge because truth
is ONLY verified as a formal proof to theorem consequences:
∀F ∈ Formal_Systems ∀x ∈ WFF(F) (True(F, x) ↔ (F ⊢ x))
When this above formula is accepted as the correct formalization of Truth,
then Tarski and Gödel are both refuted.
OK, that may be something we could disagree about. I understand truth to be essentially another name for whatever it is we believe. We believe it's night, then we say it's true it's night. Logic then is merely the syntactic relation between our beliefs. We can't verify our beliefs anyway, but it's clearly a good idea to have "coherent" beliefs so our brain evolved to make sure we do, up to a point. Truth still as a value for each of us. There are things you can say that are true, just because there are things you know, like how you feel and whether you're hungry or pissed off. But that's not enough to discuss with each other and that's not enough even to think the world around you. So you need logic to think up the world around you, and also, secondarily, to exchange with other people "linguistically", something which has only become very important since perhaps 10,000 to 40,000 years ago. The point here is that logic is first a mental process evolved by natural selection over more than 525 million years and an intuitive capability we all have, and only secondarily a formal system, which as such is a part of nearly all human languages. As I understand it, the formal system we use is only a partial expression of the mental capability we have. Logic comes first, formalisation comes second, and then maybe not quite the thing. Still, this gives us a number of "logical truths" we all think are true, although we can choose not to, just because logical truths are formal logic, ergo part of language, and that we can invent and say pretty much anything. Our intuitive brain couldn't, though. This explains for example how mathematicians could choose, after Russell, to move away from their own logical intuition. Basically, mathematical logic is mathematics, not logic.
So, I agree with your definition of truth here, but only insofar as it is conceived as "formal truth", which of course goes without saying given the way it is defined. My point, though, is that we may want to keep in mind that this "formal truth" isn't quite truth as our brain intuit it.
In effect, your definition makes truth dependent on the formal system. There's no other way for formal truth but, again, that ain't really truth either.
PeteOlcott wrote: ↑Sun Mar 24, 2019 4:02 pm
then Tarski and Gödel are both refuted.
My brain says he feels good about that.
EB