The folloing is an Edit of the previous question. By stratified [acyclic ZF][1], it is meant acylic ZF but with restricting Separation and Replacement to stratified instances of them and forbid the use of symbol $\mathcal R$ them. >Is Stratified acyclic ZF consistent with having an *internal* non-trivial automorphism $j$ from $V$ to $V$? That is we add a new primitive one place function symbol $j$ to the language of ZF, and add the axioms of $j$ being an automorphism over the whole universe of discourse, that is: **Bijectivity:** $\forall x \exists y : j(x)=y \\\forall y \exists x: j(x)=y$ **Isomorphism:** $\forall x \forall y :x \in y \iff j(x) \in j(y)$ **Collapse:** $\exists \alpha: V_\alpha \subsetneq V_{j(\alpha)}$ Where $``j"$ is allowed to appear in instances of the stratified separation and replacement. > If this is allowed what would be the consistency strength of such addition? [1]: https://mathoverflow.net/questions/383773/is-acyclic-zf-consistent