Groups | Search | Server Info | Login | Register

Groups > comp.theory > #21912

Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR)

Cross-posted to 4 groups.

Show all headers | View raw

On 7/24/2020 5:47 PM, Keith Thompson wrote:
> olcott <NoOne@NoWhere.com> writes:
>> Logical implication
>>      p  q  p ⇒ q
>> (a) T  T    T
>> (b) T  F    F
>> (c) F  T    T
>> (d) F  F    T
>>
>> p = "I will go to the store"
>> q = "I will buy eggs at the store"
>>
>> (a) I will go to the store and buy eggs while I am there is true
>> (b) I will go to the store and not buy eggs while I am there is false
>> (c) I will not go to the store and buy eggs while I am there is true
>> (d) I will not go to the store and not buy eggs while I am there is true
>>
>> (c) I will not go to the store and buy eggs while I am there is true
>> Proves that Logical implication derives incorrect consequences
> 
> No, it doesn't.  (c) just means if it were the case that you don't go to
> the the store *and* you buy eggs at the store, p ⇒ q is still true.  The
> fact that that's not possible 

You can't buy egqs AT THE STORE remotely

(unless you buy eggs remotely? or maybe
> you were born at the store?) doesn't make the conclusion invalid,
> because that's what "p ⇒ q" *means*.
> 

Then "p ⇒ q" is a fricking God damned liar thus proving that symbolic 
logic is broken.

> The impossibility of buying eggs without going to the store is outside
> the scope of the original statement, and "p ⇒ q" doesn't say either than
> you can do that or that you can't.  Choosing an example that has
> implications beyond the meaning of "p ⇒ q" doesn't make "p ⇒ q" invalid.
> 
> Let p be "it rains" and q be "I will carry an umbrella", so p ⇒ q is "If
> it rains, then I will carry an umbrella".  (Note that "⇒" doesn't carry
> the same implication of causation that the English if/then construct
> sometimes does.)  If it *doesn't* rain tomorrow but I carry an umbrella
> anyway (which is of course quite possible), that doesn't falsify the
> statement that "If it rains, then I will carry an umbrella".
> 
> In other words, the statement
>      If it rains, then I will carry an umbrella
> is consistent with:
>      It rains and I carry an umbrella.
>      It doesn't rain and I carry an umbrella.
>      It doesn't rain and I don't carry an umbrella.
> but inconsistent with
>      It rains and I don't carry an umbrella.
> Only that last set of circumstances falsifies "p ⇒ q".
> 
> Yet again, you try to refute a statement in mathematical logic because
> you dislike the way it's expressed in informal English words.
> 


-- 
Copyright 2020 Pete Olcott

Back to comp.theory | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-24 17:26 -0500
  Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) David Kleinecke <dkleinecke@gmail.com> - 2020-07-24 15:45 -0700
    Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-24 17:53 -0500
      Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) Kaz Kylheku <793-849-0957@kylheku.com> - 2020-07-24 23:55 +0000
  Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-07-24 15:47 -0700
    Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-24 17:57 -0500
      Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-07-24 16:19 -0700
        Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-24 19:20 -0500
          Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-07-24 18:29 -0700
            Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-25 23:14 -0500
              Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) André G. Isaak <agisaak@gm.invalid> - 2020-07-25 23:13 -0600
      Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-07-25 00:34 +0100
        Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-24 19:51 -0500
          Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) André G. Isaak <agisaak@gm.invalid> - 2020-07-24 19:29 -0600
            Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) olcott <NoOne@NoWhere.com> - 2020-07-25 23:04 -0500
              Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) André G. Isaak <agisaak@gm.invalid> - 2020-07-25 23:05 -0600
          Re: Simply defining Gödel Incompleteness and Tarski Undefinability away V34 (Logical implication ERROR) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-07-25 02:39 +0100

csiph-web