Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι → ι be given.
Let x3 of type ι → ι be given.
Let x4 of type ι be given.
Apply Unj_Inj0_eq with
x4,
λ x5 x6 . If_i (Inj0 x4 = Inj0 x6) (x2 x6) (x3 x6) = x2 x4.
Apply If_i_1 with
Inj0 x4 = Inj0 x4,
x2 x4,
x3 x4.
Let x5 of type ι → ι → ο be given.
The subproof is completed by applying H0.