[FRIAM] talking to bots is fun for everyone

[Frank Wimberly]

A implies B is false iff A is true and B is false.

---
Frank C. Wimberly
140 Calle Ojo Feliz,
Santa Fe, NM 87505

505 670-9918
Santa Fe, NM

On Tue, Dec 27, 2022, 10:15 AM David Eric Smith <desmith at santafe.edu> wrote:

> Are you sure Frank?
>
> The sentence from gtp that I highlight said:
>
> "⊃" is the logical symbol for "implies." It is used to form conditional
>> statements in which the formula on the right is true only if the formula on
>> the left is true.
>
>
> As I understand “implies” (or just the conditional if A then B), it means
> that the formula on the right is true _if_ the formula on the left is
> true.  Not “only if” as gtp is quoted to say above.  Correct would be “the
> formula on the right is _false_ _only if_ the formula on the left is
> _false_.  Conditional doesn’t say anything about whether B is true or false
> if A is not true.
>
> Eric
>
>
>
> On Dec 27, 2022, at 11:46 AM, Frank Wimberly <wimberly3 at gmail.com> wrote:
>
> I've taken courses in formal logic at multiple levels.  All that notation
> is familiar and the explanation seems correct if vacuous.
>
> ---
> Frank C. Wimberly
> 140 Calle Ojo Feliz,
> Santa Fe, NM 87505
>
> 505 670-9918
> Santa Fe, NM
>
> On Tue, Dec 27, 2022, 3:19 AM David Eric Smith <desmith at santafe.edu>
> wrote:
>
>> Interesting.  Lack of global awareness duly noted.
>>
>> But also, can you check me on this?:
>>
>> > On Dec 26, 2022, at 7:21 PM, glen <gepropella at gmail.com> wrote:
>> >
>> > This exchange was interesting. I've never seen ⊃° used.
>> >
>> > ⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄⋄
>> > me: What is the difference between ⊃ and ⊢.
>> >
>> > gpt: The symbol "⊃" is the logical symbol for "implies." It is used to
>> form conditional statements in which the formula on the right is true only
>> if the formula on the left is true. For example, the formula "A ⊃ B" can be
>> read as "A implies B," and it means that if A is true, then B must also be
>> true.
>>
>> Am I somehow blanking on ordinary sign-flips, or mistaking left and right?
>>
>> Seems B Is true _if_ A is true.  B is false _only if_ A is false == If A
>> is true, then B must also be true.
>>
>> Given that English is not ensured to have any global internal logical
>> consistency, one can see making sentences that don’t close internally.  But
>> in areas where English is capable of being used with internal consistency,
>> I am surprised to see an “only if” transposed with an “if” everywhere.  Did
>> I completely misunderstand what “implies” means?
>>
>>
>> On all this I feel completely exposed: I thought I remembered from
>> Quine’s little book on propositional calculus that “implies” isn’t even an
>> elementary operator; only enters in a context like modus ponens for
>> proofs.  In first-order logic one was supposed to write expressions such as
>> “B or not(A)” to mean “if A then B”.  And there was some other symbol (even
>> simpler than the entails) for that conditional.
>>
>> Eric
>>
>>
>>
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