Re: Help with a problem

On Wed, 23 Nov 2005, Robert Zimmerman wrote:
> Chris Menzel <cmenzel@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> > On Wed, 23 Nov 2005 04:49:35 GMT, Robert Zimmerman <rfz1@xxxxxxxxxxxx> said:
> > > I'm am learning logic from Copi's book (as a hobby). There is an
> > > advanced problem:
> > >
> > > With the rules of inference, prove the validity of:
> > >
> > > A
> > > therefore B v ~B
> > >
> > > I am horribly stuck. Any help would be appreciated. I'm losing sleep.
> >
> > What rules of inference do you have available?
>
> The "19 rules of inference" from Copi's book "Intro to Logic" (that's
> the short answer). i.e. mp, mt, hs, ds, cd, etc etc.
>
Huh? mp is MP, modus ponens? Don't recoginze any other of the jargon
you're using tho I suppose with a hand waving or two etc's, all
wonderfuls and all blunderfulls could be.

Here's natural deduction proof with classical negation
leaving reasons, rules and references for the reader.

assume ~(p v ~p)
(p v ~p) -> f
assume p
p v ~p
f
p -> f
~p
p v ~p
f
~(p v ~p) -> f
p v ~p
.