Section Sound_Kripke.
Context {L: Language}
{minL: MinimumLanguage L}
{pL: PropositionalLanguage L}
{mL: ModalLanguage L}
{MD: Model}
{kMD: KripkeModel MD}
{M: Kmodel}
{R: Relation (Kworlds M)}
{SM: Semantics L MD}
{tminSM: TrivialMinimumSemantics L MD SM}
{tpSM: TrivialPropositionalSemantics L MD SM}
{kmSM: KripkeModalSemantics L MD M SM}.

Lemma sound_rule_N:
forall x,
(forall (m: Kworlds M), KRIPKE: M, m |= x) ->
(forall (m: Kworlds M), KRIPKE: M, m |= boxp x).