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

Lemma DeductionWeaken_ContextualDerivableFiniteWitnessed_DeductionSubst1_2_DeductionSubst:
DeductionWeaken L Gamma ->
ContextualDerivableFiniteWitnessed L Gamma ->
DeductionSubst1 L Gamma ->
DeductionSubst L Gamma.