. apply membership_iff.mpr;
  exact disj₂'! (membership_iff.mp hq);
case mpr.inr
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : Inhabited α
L : DeductionParameter α
inst✝ : L.Normal
Ω Ω₁ Ω₂ : MCT L
p q : Formula α
hq : q ∈ Ω.theory
⊢ p ⋎ q ∈ Ω.theory
no goals