They can indeed be used together and are interdépendant in practice at "high level mathematics" But set theory is made of a lower level primitive (first order l

They can indeed be used together and are interdépendant in practice at "high level mathematics" But set theory is made of a lower level primitive (first order logic) itself being an extension of zeroth order logic. I was saying that in the context of learning the foundation of mathematics where set theory is not the first place to begin.