Consider the following premises. forall x: S(x). forall z: T(z) -> S(z). forall z: S(z) -> T(z). Can we infer T(f) from them?
 From forall z: S(z) -> T(z), forall z: T(z) -> S(z) we can infer forall z: S(z) <-> T(z). From forall x: S(x) we can infer S(f). From forall z: S(z) <-> T(z) we can infer S(f) <-> T(f). From S(f) <-> T(f) we can infer S(f) -> T(f). Finally, from S(f) -> T(f), S(f) we can infer T(f). Therefore, the answer is yes.