Abstract

A main thesis of Fred Sommers' type theory, is that an isomorphism exists between any natural language and the categories discriminated by that language. Here the author gives an explanation of what this claim comes to. And then it is argued that, so understood, the claim is incompatible with Zermelo-Fraenkel set theory. Finally, it is argued against trying to salvage the isomorphism thesis by appealing to some other set theory.