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