Class ModalStable (L: Language) {minL: MinimunLanguage L} {mL: ModalLanguage L} (Gamma: ProofTheory L) (stable: expr -> Prop) := {
  boxp_stable: forall x, stable x -> stable (boxp x)
}.Class ModalStable (L: Language) {minL: MinimunLanguage L} {mL: ModalLanguage L} (Gamma: ProofTheory L) (stable: expr -> Prop) := {
  boxp_stable: forall x, stable x -> stable (boxp x)
}.

Lemma truep_stable {L: Language} {minL: MinimunLanguage L} {pL: PropositionalLanguage L} {Gamma: ProofTheory L} {stable: expr -> Prop} {pstable: PropositionalStable L Gamma stable}: stable TT.