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Topic:
Hereditary size notion proving consistency of ZF
Replies:
1
Last Post:
Jan 20, 2013 9:34 AM




Re: Hereditary size notion proving consistency of ZF
Posted:
Jan 20, 2013 9:34 AM


On Jan 19, 9:20 pm, Zuhair <zaljo...@gmail.com> wrote: > I think that ZF can be proved consistent relative to consistency of > the following theory defined in the same language of ZF with the > following axioms: > > Define: Set(x) iff Exist y. x in y > > [1] Extensionality: as in Z > > [2] Comprehension: If phi is a formula in which x is not free, then > (Exist x. for all y. y in x iff Set(y) & phi) is an axiom. > > [3] Pairing: (for all y. y in x > y=a or y=b) > Set(x) > > [4] Size: [Set(x) & y < x & for all m in z (m << Uy)] > Set(z) >
If we remove the condition y < x and replace Uy with x then this would be sufficient to prove the consistency of Z.
> Definitions: > > y < x is defined as: Exist s,f: s subset_of x & f:s > y & f is > surjective. > > y << x is defined as: y < x & (for all z in TC(y). z < x) > > TC(y)=x iff [for all z. z in x iff (for all s. y subset_of s & s is > transitive > z in s)] > > Uy=x iff [for all z. z in x iff Exist k. k in y & z in k] > > /



