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Re: Erroneous conclusions from applying material conditionals?

Newsgroups sci.logic
Date 2023-06-01 23:26 -0700
References (19 earlier) <a521e98c-6f4f-4748-8e27-1b76497b7aebn@googlegroups.com> <50b495b4-da9e-4959-b231-659493454ce0n@googlegroups.com> <1f26da1c-66ca-4271-9397-4a993a4ebc96n@googlegroups.com> <053bbc26-42f1-4efa-bb55-6b322c1ffa70n@googlegroups.com> <0301de03-a2b1-4e10-9652-a98acc1e98e6n@googlegroups.com>
Message-ID <035d1bf8-edfe-49fe-845f-9bda7146e3f2n@googlegroups.com> (permalink)
Subject Re: Erroneous conclusions from applying material conditionals?
From Dan Christensen <Dan_Christensen@sympatico.ca>

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On Friday, June 2, 2023 at 1:02:45 AM UTC-4, Ross Finlayson wrote:

[snip]

> Now, I can understand that's very widespread, but also that most people 
> have never gone into the derivations, where what would be the "completion", 
> brings in the necessity of an ontological commitment _in the derivation_ what 
> must be _in the logic_, to universal quantification and such. I.e. it breaks 
> there, like I said above. 
> 

The truth table of logical (material) implication:

A B A=>B
T T T
T F F
F T T
F F T

In daily discourse about the present state of the world, the first two lines are routinely used. The last two are rarely if ever use. We don't usually give any consideration about implications with false antecedents (A). The last two lines are typically only used in very technical arguments, e.g. in mathematical proofs. They are, however, easily derivable from first principles (see my proof here).

> Also, I can understand that's very widespread, but most people do not use 
> it at all, because to them it says "a lie implies my truth" which is not reasonable 
> to these people, and instead they use "really: classical propositional calculus". 
> 

Again, if the antecedent A is false, then the implication A=>B (but not necessarily the consequent B) must be true.

> 
> Then, about the order of your premises, and their discharge, 
> why can't you re-order your premises? 

[snip]

You could reorder your premises, but you will likely not obtain the same result. If you interchange the first two premises in my proof, you would get A=>[~A=>B] instead of ~A=>[A=>B].

> Because, that's just stipulating "this is logical, now forget it", 
> really, I think best you can do is make "material implication" 
> a premise and then separate out the parts for direct implication 
> contra "vacuous placeholder". 
> 
> So, I definitely point at "showing a contradiction in terms 
> negates an unrelated term" as _false_.

No errors or inconsistencies here. Try again.

Dan

Download my DC Proof 2.0 freeware at http://www.dcproof.com
Visit my Math Blog at http://www.dcproof.wordpress.com

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Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-27 12:04 -0700
  Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-27 13:25 -0700
    Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-27 19:42 -0700
  Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 08:39 -0700
    Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 11:50 -0700
    Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 12:01 -0700
      Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 13:47 -0700
        Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 13:57 -0700
          Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 14:02 -0700
          Re: Erroneous conclusions from applying material conditionals? olcott <polcott2@gmail.com> - 2023-05-28 16:12 -0500
          Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 15:39 -0700
            Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 15:56 -0700
              Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 16:04 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 16:14 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 16:24 -0700
              Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 16:49 -0700
              Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 16:52 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <janburse@fastmail.fm> - 2023-05-29 02:25 +0200
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <janburse@fastmail.fm> - 2023-05-29 02:31 +0200
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <janburse@fastmail.fm> - 2023-05-29 02:45 +0200
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 17:59 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 17:46 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 17:51 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 18:01 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 18:07 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 18:12 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 18:15 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 18:17 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 18:23 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-28 18:28 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 18:46 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-28 21:51 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-28 22:14 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 22:33 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 22:36 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-29 09:01 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 09:27 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 09:32 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 09:35 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 10:03 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <janburse@fastmail.fm> - 2023-05-29 19:45 +0200
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-30 05:52 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-30 15:16 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-29 11:14 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-29 22:53 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-30 17:45 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-05-31 08:23 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-31 13:22 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-31 13:31 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-31 13:38 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-31 13:51 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-06-01 19:56 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-06-01 21:35 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 21:44 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 18:54 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-06-01 19:55 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 21:13 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 21:19 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 21:23 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 21:30 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-06-01 22:02 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 22:28 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 22:31 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 22:34 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 22:39 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 23:29 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-03 14:14 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-03 14:23 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 23:26 -0700
                Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-06-02 09:42 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 20:41 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 20:58 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 21:24 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 21:28 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 21:31 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-01 21:34 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-06-01 22:49 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-03 04:49 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-03 04:51 -0700
        Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-28 15:33 -0700
    Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 02:52 -0700
      Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 02:58 -0700
        Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 03:03 -0700
          Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 07:35 -0700
            Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 08:23 -0700
              Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 08:30 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 08:33 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 09:56 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <janburse@fastmail.fm> - 2023-05-29 19:56 +0200
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 11:40 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 11:43 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 13:32 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 13:38 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 13:59 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 15:19 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 15:21 -0700
                Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-05-29 17:37 -0700
                Re: Erroneous conclusions from applying material conditionals? Dan Christensen <Dan_Christensen@sympatico.ca> - 2023-05-29 19:00 -0700
  Re: Erroneous conclusions from applying material conditionals? Mild Shock <janburse@fastmail.fm> - 2023-06-02 09:41 +0200
    Re: Erroneous conclusions from applying material conditionals? Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-06-02 09:42 -0700
      Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-02 11:00 -0700
        Re: Erroneous conclusions from applying material conditionals? Mild Shock <bursejan@gmail.com> - 2023-06-02 11:14 -0700

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