Let x0 of type ι → ι → ο be given.
Apply unknownprop_e890bcc7203f5eafb26afacae8b51624f0e9604ffee0ae1d4821f4551ac34a63 with
λ x1 x2 : (ι → ι → ο) → ο . (∀ x3 x4 x5 . x0 x3 x4 ⟶ x0 x4 x5 ⟶ x0 x3 x5) ⟶ x2 x0.
Assume H0: ∀ x1 x2 x3 . x0 x1 x2 ⟶ x0 x2 x3 ⟶ x0 x1 x3.
The subproof is completed by applying H0.