ZFC invalid due to axiom of seperation- russell paradox still stands
the australian philospher colin leslie dean points out poincare and russell argued that impredicative statements led to paradox in mathenmatics
zermelo ad hoc introduced the axiom of seperation to outlaw the russell paradox which showed naive set theory to be inconsistent
but this axiom is invalid as it is impredicative
thus it cant be used to outlaw russells paradox
thus russells paradox still stands
http://en.wikipedia.org/wiki/Zermelo...kel_set_theory
3. Axiom schema of specification (also called the axiom schema of
separation or of restricted comprehension): If z is a set, and \phi\! is
any property which may characterize the elements x of z, then there is a
subset y of z containing those x in z which satisfy the property. The
"restriction" to z is necessary to avoid Russell's paradox and its
variant
poincare and russell argued that impredicative statements led to paradox
in mathenmatics
now
the seperation axiom of ZFC is impredicative
solomon ferferman
http://math.stanford.edu/~feferman/p...dicativity.pdf
"in ZF the fundamental source of impredicativity is the seperation axiom
which asserts that for each well formed function p(x)of the language ZF
the existence of the set x : x } a ^ p(x) for any set a Since the formular
p may contain quantifiers ranging over the supposed "totality" of all the
sets this is impredicativity according to the VCP
this impredicativity is given teeth by the axiom of infinity "
thus by useing an invalid axiom ZFC becomes invalid