Proofgold Proof

pf
Let x0 of type ι → ι be given. Let x1 of type ι → ο be given. Assume H0: ∀ x2 . x1 x2 ⟶ x1 (x0 x2). Let x2 of type ι be given. Assume H1: x1 x2. Apply H0 with x0 x2. Apply H0 with x2. The subproof is completed by applying H1. ■