A strengthening of Scott's ${\rm ZF}^{ ot=}$ result.
Stephen B Pollard · Notre Dame Journal of Formal Logic · 1990
Scott's proof that ZF is not interpretable in ZF-minusextensionality can be transformed into a proof that a theory much weaker than ZF is not interpretable in ZF-minus-extensionality.In [6], Scott established that ZF is not interpretable in ZF* (ZF-minus-Extensionality). 1 In particular, he showed: