Re: A question about ackermann's set theory.

On Tue, 30 Oct 2007 14:43:56 -0700, Zaljohar@xxxxxxxxx wrote:


Ackermann's set theory is present at

http://en.wikipedia.org/wiki/Ackermann_set_theory

One thing I don't understand is the reflection axiom schema

Concerning the comprehension schema they mentioned the following
restriction:

"[...] Let F(y, z_1, ..., z_n) be any formula which does not contain the
constant symbol V or the variable x free."

Maybe they forgot the mention a comparable restriction for the
reflection axiom schema (if so)?


My objection is the following:

Let F(y)<->(y e V & y is an ordinal)

This would violate the mentioned restriction (if so), since F(y) would
contain the symbol "V".


F.

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