FOM: well-founded extensional relations

Kanovei kanovei at
Fri Jun 16 11:30:21 EDT 2000

>From: holmes at
>Date: Wed, 14 Jun 2000 12:22:28 -0600

>I agree with Thomas that Roland Hinnion is responsible for introducing
>the well-founded relation interpretation of Zermelo-style set theory
>in NF.  I would be surprised to find that he was the first person to
>consider interpreting Zermelo-style set theory using well-founded
>extensional relations in a general context; I would be interested to
>hear if anyone knows about the history of this idea.
>                                  --Randall Holmes

Maybe the biggest element of this history is the following: 
interpretation of different fragments of ZF in different 
versions of 2nd order PA, that goes back to 70s if not to 60s. 


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