Re: Need help with a simple logic proof.

On Mar 9, 11:03 pm, G. Frege <nomail@invalid> wrote:
On Fri, 09 Mar 2007 23:56:05 +0100, G. Frege <nomail@invalid> wrote:

Problem is, that the OP seems to have to use one of Copi's ugly systems of
"natural deduction" (or a descendant of one of his systems). So it's hard
to say which rules are allowed and which are not. Actually, I simply don't
remember all those rules, not even of ONE of his (various) systems. :-(

The OP wrote:

"[Allowed rules are:] modus ponens, modus tollens, hypothetical syllogism,
disjunctive syllogism, constructive dilemma, conjunction, simplification,
addition, transposition, material implication, material equivalence,
exportation, tautology, De Morgan's theorem, computation, association,
distribution, and double negation."

!!! sigh !!!

Copi's systems really should be banned ... imho! :-(((

F.


I agree with this,
Only Suppes/ Lemmon style proofs should be prefered.
For the diehards, Gentzen (tree) style is also OK

But Copy and Quinne style proofs ban them.
And EI is not a valid rule.

.