Section DerivableRulesFromAxiomatization2.
Context {L: Language}
{minL: MinimumLanguage L}
{pL: PropositionalLanguage L}
{Gamma: Provable L}
{minAX: MinimumAxiomatization L Gamma}
{ipAX: IntuitionisticPropositionalLogic L Gamma}
{cpAX: ClassicalPropositionalLogic L Gamma}.

Lemma impp2orp: forall (x y: expr),
|-- (x --> y) <--> (~~ x || y).