Lemma ctx_wff_mutual : (forall G0 a A, Typing G0 a A -> Ctx G0) /\ (forall G0 phi, PropWff G0 phi -> Ctx G0) /\ (forall G0 D p1 p2, Iso G0 D p1 p2 -> Ctx G0) /\ (forall G0 D A B T, DefEq G0 D A B T -> Ctx G0) /\ (forall G0, Ctx G0 -> True).