Let x0 of type ι be given.
Let x1 of type ι → ι be given.
Let x2 of type ι be given.
Assume H0:
In x2 (Repl x0 (λ x3 . x1 x3)).
Apply unknownprop_89e422bb3b8a01dd209d7f2f210df650a435fc3e6005e0f59c57a5e7a59a6d0e with
x0,
x1,
x2,
False.
The subproof is completed by applying H0.