Re: Answer "how to prove ~(P <--> Q) |- ~P <-->Q "



Frederick Williams wrote:
herbzet wrote:

Just btw, I don't recall my first book on logic, but one of
the first was A.N. Prior's "Formal Logic" which was strictly
Hilbert-style, and in Polish notation. Loved it.

Oh yes, a fabulous book. My maths tutor didn't like it because it's got
more words than symbols. I liked it because it introduced me to
Le\'sniewski's systems, Tarski's definition of and in terms of iff and
this wonderful axiom from which (with the appropriate rules) follows PC
with functor variables and quantifiers: C delta delta 0 p. Not the kind
of stuff you'll find in most logic texts.

Yeah, baby! _Lots_ of good stuff!

There is also a brief reference to natural deduction in the style of
Ja\'skowski.

In an appendix, I think.

My remarks apply to the corrected printing of the second edition.

Right.

--
hz
.