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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: sci.logic
Subject: Re: Undecidability based on epistemological antinomies V2 --Tarski Proof--
Date: Mon, 22 Apr 2024 12:35:16 +0300
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On 2024-04-21 14:44:37 +0000, olcott said:

> On 4/21/2024 2:57 AM, Mikko wrote:
>> On 2024-04-20 15:20:05 +0000, olcott said:
>> 
>>> On 4/20/2024 2:54 AM, Mikko wrote:
>>>> On 2024-04-19 18:04:48 +0000, olcott said:
>>>> 
>>>>> When we create a three-valued logic system that has these
>>>>> three values: {True, False, Nonsense}
>>>>> https://en.wikipedia.org/wiki/Three-valued_logic
>>>> 
>>>> Such three valued logic has the problem that a tautology of the
>>>> ordinary propositional logic cannot be trusted to be true. For
>>>> example, in ordinary logic A ∨ ¬A is always true. This means that
>>>> some ordinary proofs of ordinary theorems are no longer valid and
>>>> you need to accept the possibility that a theory that is complete
>>>> in ordinary logic is incomplete in your logic.
>>>> 
>>> 
>>> I only used three-valued logic as a teaching device. Whenever an
>>> expression of language has the value of {Nonsense} then it is
>>> rejected and not allowed to be used in any logical operations. It
>>> is basically invalid input.
>> 
>> You cannot teach because you lack necessary skills. Therefore you
>> don't need any teaching device.
>> 
> 
> That is too close to ad homimen.
> If you think my reasoning is incorrect then point to the error
> in my reasoning. Saying that in your opinion I am a bad teacher
> is too close to ad hominem because it refers to your opinion of
> me and utterly bypasses any of my reasoning.

No, it isn't. You introduced youtself as a topic of discussion so
you are a legitimate topic of discussion.

I didn't claim that there be any reasoning, incorrect or otherwise.

>> As you make the syntax of your language dependent on semantics
>> you lose one of the greatest advantage of formal languages:
>> the simplicity of determination whether a string is a well formed
>> formula.
>> 
> 
> Not at all. By combining them together we can simultaneously determine
> syntactic and semantic correctness. By keeping them separate we have
> misconstrued expressions that are not even propositions as propositions
> that prove incompleteness and undecidability.

You have not shown that you can determine either semantic or syntactic
correctness.

> A proposition is a central concept in the philosophy of language,
> semantics, logic, and related fields, often characterized as the primary
> bearer of truth or falsity. Propositions are also often characterized as
> being the kind of thing that declarative sentences denote.
> https://en.wikipedia.org/wiki/Proposition

Therefore it were easier if you could easily check whether a particular
string is a proposition or a sequence or propositions.

-- 
Mikko