[FOM] non-extensional models of set theory

[william tait]

Robbin Gandy had a paper on that in the 1950's in JSL. I think it is the result you have in mind.

Bill 

Sent from my iPad

> On Apr 1, 2015, at 10:18 AM, Paul B Levy <P.B.Levy at cs.bham.ac.uk> wrote:
> 
> 
> Dear all,
> 
> Is there a result in the literature along the following lines?
> 
> Given a model of ZF without Extensionality, its "extensional quotient" is a model of ZF including Extensionality.
> 
> Paul
> 
> 
> 
> -- 
> Paul Blain Levy
> School of Computer Science, University of Birmingham
> http://www.cs.bham.ac.uk/~pbl
> _______________________________________________
> FOM mailing list
> FOM at cs.nyu.edu
> http://www.cs.nyu.edu/mailman/listinfo/fom