Let x0 of type ι be given.
Let x1 of type ι be given.
Apply unknownprop_8e16f01d3d7d4384aa400042b25bdc3506a8a79b3eeebecda1fd47269dd59112 with
e4431.. x0,
e4431.. x1,
λ x2 . prim1 x2 x0,
λ x2 . prim1 x2 x1.
The subproof is completed by applying H0.