case impI ih => apply impI; solve_by_elim [insert_subset_insert]
H : Type ?u.33194
inst✝ : HeytingAlgebra H
v : Variable → H
A B : Formula
Γ Γ✝ : Set Formula
A✝ B✝ : Formula
a✝ : insert A✝ Γ✝ ⊢ B✝
ih : ∀ {Δ : Set Formula}, insert A✝ Γ✝ ⊆ Δ → Δ ⊢ B✝
Δ : Set Formula
h2 : Γ✝ ⊆ Δ
⊢ Δ ⊢ A✝ ⇒ B✝
no goals