Let x0 of type ι be given.
Apply Empty_eq with
setminus x0 x0.
Let x1 of type ι be given.
Apply setminusE2 with
x0,
x0,
x1 leaving 2 subgoals.
The subproof is completed by applying H0.
Apply setminusE1 with
x0,
x0,
x1.
The subproof is completed by applying H0.