⊦ compl(f)(S)(x) ↔ ¬ f(λ x0. ¬ S(x0))(x)
S(x0), ¬ f(λ x0. ¬ ¬ S(x0))(x0), S ⊆ f(S), S(x) ⊦
Used terms: x0, λ x0. ¬ S(x0), f