 A model of NFU can be constructed as follows. Well-known results of model theory allow the construction of a nonstandard model of ZFC (actually, a model of Mac Lane set theory suffices) with an external automorphism \(j\) which moves a rank \(V_{\alpha}\). We stipulate without loss of generality that \(j(\alpha) \lt \alpha\). The universe of our model of NFU will be \(V_{\alpha}\) and the membership relation will be defined as