Section DerivableRulesFromSequentCalculus.
Context {L: Language}
{Gamma: Derivable L}
{bSC: BasicSequentCalculus L Gamma}.

Lemma contextual_derivable_finite_witnessed {fwSC: FiniteWitnessedSequentCalculus L Gamma}: forall (Phi Psi: context) (y: expr), Union _ Phi Psi |-- y -> exists xs, Forall Psi xs /\ Union _ Phi (fun x => In x xs) |-- y.