rw [not_not] at canApplyRule
LR : TNode
canApplyRule : ¬¬∃ Lcond Rcond C, Nonempty (LocalRule (Lcond, Rcond) C) ∧ Lcond ⊆ LR.1 ∧ Rcond ⊆ LR.2
⊢ Nonempty (LocalTableau LR)
LR : TNode
canApplyRule : ∃ Lcond Rcond C, Nonempty (LocalRule (Lcond, Rcond) C) ∧ Lcond ⊆ LR.1 ∧ Rcond ⊆ LR.2
⊢ Nonempty (LocalTableau LR)