Re: MV Keys
Date: 8 Mar 2006 10:03:52 -0800
Message-ID: <1141841032.284945.207650_at_v46g2000cwv.googlegroups.com>
vc wrote:
> jason.glumidge_at_gmail.com wrote:
> > vc wrote:
> > > Brian Selzer wrote:
> > > [...]
> > > > "x is 2" is a sentence; "y is 3" is a sentence.
> > > > "x is 2 and y is 3" is also a sentence.
> > >
> > > You are confused. "x is 2" is not a sentence in the contex of FOL.
> > > It's a predicate with a free variable which will become a sentence if
> > > you substitute a constant for x.
> >
> > I am a bit confused too then :(
> >
> > "There is a person whose age is 45" is a valid sentence, and that looks
> > identical to "x is 2" to me.
>
> How come ? The former is a sentence where the free variable is bound
> by the existential quantifier:
the latter you mean, no?
>
> E (x in X)(x = 2)
>
> whose truth depends on whether the set/domain X contains 2.
Anyhow reading the full paragraph of the OP does he not mean x=2 as x(2)? I did not read his shorthand to mean x was a variable. Otherwise yes it would not make sense as a 'closed' sentence. But given the flow of his arguemnt I'd give it the benefit of this interpretation before jumping on it.
> Of course, one is free to use one's private language but
> it's hardly productive.
Ok, agreed. Received on Wed Mar 08 2006 - 19:03:52 CET