Section TheoryOfSequentCalculus.
Context {L: Language}
{Gamma: Derivable L}.

Lemma DeductionWeaken_ContextualDerivableFiniteWitnessed_2_DerivableFiniteWitnessed:
DeductionWeaken L Gamma ->
ContextualDerivableFiniteWitnessed L Gamma ->
DerivableFiniteWitnessed L Gamma.