Date: Jun 12, 2013 3:24 PM
Subject: at the background of logic

I think that all logical connectives, quantifiers and identity are
derivable from a simple semi-formal inference rule denoted by "|" to
represent "infers" and this is not to be confused with the Sheffer
stroke nor any known logical connective.

A| C can be taken to mean the "negation of A"

A,B| A can be taken to mean the "conjunction of A and B"

x| phi(x) can be taken to mean: for all x. phi(x)

x, phi(y)| phi(x) can be taken to mean: x=y

The idea is that with the first case we an arbitrary proposition C is
inferred from A, this can only be always true if A was False,
otherwise we cannot infer an "arbitrary" proposition from it.

Similarly with the second case A to be inferred from A,B then both of
those must be true.

Also with the third condition to infer that for some constant
predicate phi it is true that given x we infer phi(x) only happens if
phi(x) is true for All x.

With the fourth case for an 'arbitrary' predicate phi if phi(y) is
true and given x we infer that phi(x) is true, then x must be
identical to y.

Anyhow the above kind of inference is somewhat vague really, it needs
to be further scrutinized.