Apply SNoLev_ind with
λ x0 . ∀ x1 x2 . SNoCutP x1 x2 ⟶ x0 = SNoCut x1 x2 ⟶ minus_SNo x0 = SNoCut {minus_SNo x3|x3 ∈ x2} {minus_SNo x3|x3 ∈ x1}.
Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι be given.
Apply H2 with
x0 = SNoCut x1 x2 ⟶ minus_SNo x0 = SNoCut {minus_SNo x3|x3 ∈ x2} {minus_SNo x3|x3 ∈ x1}.
Assume H3:
and (∀ x3 . x3 ∈ x1 ⟶ SNo x3) (∀ x3 . x3 ∈ x2 ⟶ SNo x3).
Apply H3 with
(∀ x3 . x3 ∈ x1 ⟶ ∀ x4 . x4 ∈ x2 ⟶ SNoLt x3 x4) ⟶ x0 = SNoCut x1 x2 ⟶ minus_SNo x0 = SNoCut {minus_SNo x3|x3 ∈ x2} {minus_SNo x3|x3 ∈ x1}.
Assume H4:
∀ x3 . x3 ∈ x1 ⟶ SNo x3.
Assume H5:
∀ x3 . x3 ∈ x2 ⟶ SNo x3.
Assume H6:
∀ x3 . x3 ∈ x1 ⟶ ∀ x4 . x4 ∈ x2 ⟶ SNoLt x3 x4.