leaving 2 subgoals.
Let x0 of type ι be given.
Assume H1:
∀ x1 . x1 ∈ x0 ⟶ nat_p x1.
Let x1 of type ι be given.
Apply ordsuccE with
x0,
x1,
nat_p x1 leaving 3 subgoals.
The subproof is completed by applying H2.
Assume H3: x1 ∈ x0.
Apply H1 with
x1.
The subproof is completed by applying H3.
Assume H3: x1 = x0.
Apply H3 with
λ x2 x3 . nat_p x3.
The subproof is completed by applying H0.