Let x0 of type ι be given.
Let x1 of type ο be given.
Assume H1:
∀ x2 . x2 ∈ omega ⟶ x0 = ordsucc x2 ⟶ x1.
Apply setminusE with
omega,
1,
x0,
x1 leaving 2 subgoals.
The subproof is completed by applying H0.
Assume H2:
x0 ∈ omega.
Apply omega_nat_p with
x0.
The subproof is completed by applying H2.
Apply nat_inv with
x0,
x1 leaving 3 subgoals.
The subproof is completed by applying L4.
Assume H5: x0 = 0.
Apply FalseE with
x1.
Apply H3.
Apply H5 with
λ x2 x3 . x3 ∈ 1.
The subproof is completed by applying In_0_1.
Apply H5 with
x1.
Let x2 of type ι be given.
Apply H6 with
x1.
Apply H1 with
x2 leaving 2 subgoals.
Apply nat_p_omega with
x2.
The subproof is completed by applying H7.
The subproof is completed by applying H8.