Let x0 of type ι be given.
Let x1 of type ι be given.
Apply unknownprop_ebc21f8cd65d757359d6a863b7db31d49a5e6720ea3dbcfcae6a70fd683799e3 with
x0,
x1.
Let x2 of type ι → ι → ο be given.
The subproof is completed by applying H0 with λ x3 x4 . x2 x4 x3.