Let x0 of type ι → (ι → ι → ι) → ι → ι be given.
Let x1 of type ι be given.
Let x2 of type ι → ι → ι be given.
Let x3 of type ι be given.
Assume H0:
∀ x4 : ι → ι → ι . (∀ x5 . prim1 x5 x1 ⟶ ∀ x6 . prim1 x6 x1 ⟶ x2 x5 x6 = x4 x5 x6) ⟶ x0 x1 x4 x3 = x0 x1 x2 x3.