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Topic: Ping David C Ullrich
Replies: 94   Last Post: Jun 26, 2013 5:55 PM

 Messages: [ Previous | Next ]
 Peter Percival Posts: 2,623 Registered: 10/25/10
Re: Ping David C Ullrich
Posted: Jun 22, 2013 12:43 PM

William Elliot wrote:
> On Sat, 22 Jun 2013, Peter Percival wrote:
>

>> Did you ever express the opinion that the continuum hypothesis was neither
>> true nor false? I seem to recall that you did but I might be mistaken. If
>> you did, why so?

>
> CH is undecidable, that is neither CH nor not-CH can be proved with ZFC.
> As for being true or false, that's a philosophical problem of no concern.

May I ask you, what does the "not" in "not-CH" mean? CH is not
especially relevant to what I'm asking, so what does "not" in "not-P"
mean, where "P" is any statement? This seems at least a partial
explanation to me:

not-P is false if P is true
not-P is true if P is false

_If_ all statements are true or false, then that seems a pretty good
explanation of the meaning of "not", *so long as* the notions of truth
and falsity are clear.

If, on the other hand, truth and falsity are to be dismissed as of no
concern, then it seems "not" (and thus "not-CH") must be dismissed as
well. It may be that you don't wish to dismiss truth and falsity as of
no concern in general, but just in the CH and similar cases. My worry:
how extensive are the similar cases?

Another account might be:

not-P is just P with (say) "~" stuck in front of it;
furthermore, if P is a statement the so is not-P;
further furthermore that "~" may be manipulated according
to certain, otherwise meaningless, rules

which leaves me unsatisfied.

[None of the above is well expressed, sorry.]

--
I think I am an Elephant,
Behind another Elephant
Behind /another/ Elephant who isn't really there....
A.A. Milne

Date Subject Author
6/21/13 Peter Percival
6/21/13 William Elliot
6/21/13 Peter Percival
6/22/13 Peter Percival
6/22/13 fom
6/25/13 Shmuel (Seymour J.) Metz
6/25/13 Peter Percival
6/25/13 Shmuel (Seymour J.) Metz
6/26/13 fom
6/26/13 fom
6/26/13 FredJeffries@gmail.com
6/26/13 fom
6/25/13 fom
6/22/13 David C. Ullrich
6/22/13 Peter Percival
6/23/13 David C. Ullrich
6/23/13 Peter Percival
6/23/13 namducnguyen
6/23/13 Peter Percival
6/23/13 namducnguyen
6/23/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 David C. Ullrich
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 fom
6/24/13 namducnguyen
6/24/13 fom
6/24/13 namducnguyen
6/25/13 Peter Percival
6/25/13 Peter Percival
6/25/13 namducnguyen
6/25/13 Peter Percival
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 namducnguyen
6/25/13 Peter Percival
6/25/13 Shmuel (Seymour J.) Metz
6/23/13 Paul
6/23/13 Peter Percival
6/23/13 Paul
6/24/13 Peter Percival
6/24/13 mueckenh@rz.fh-augsburg.de
6/24/13 Virgil
6/24/13 mueckenh@rz.fh-augsburg.de
6/24/13 Tucsondrew@me.com
6/24/13 mueckenh@rz.fh-augsburg.de
6/24/13 Virgil
6/24/13 Virgil
6/24/13 mueckenh@rz.fh-augsburg.de
6/24/13 Virgil
6/24/13 David C. Ullrich
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 namducnguyen
6/24/13 Peter Percival
6/24/13 fom
6/22/13 Paul
6/22/13 fom
6/22/13 Paul
6/23/13 Peter Percival
6/23/13 Peter Percival
6/23/13 FredJeffries@gmail.com
6/23/13 Peter Percival
6/24/13 David C. Ullrich