Despite the neo-positivistic efforts to eliminate metaphysics, the relation between science and metaphysics remains one of the great themes of philosophical discussion. Still, logical neo-positivism, even in its decline, continues to have influence. The recent publication of E. Agazzi's Filosofia della natura offers an opportunity to reflect on this topic. The aim of the present article is to show, first of all, that science itself has its own metaphysics: the image of the scientist who investigates without having metaphysical hypotheses in mind is a myth. Moreover, if we understand metaphysics as the explication of the general conditions of the intelligibility of the real, it is easy to perceive that science is based upon certain presuppositions that have a transcendental character. From this it follows that there is a minimal sense of the term "metaphysics" which proves impossible to renounce. Since no one can exempt himself from having certain fundamental ideas about the real, neither are scientists exempt from this rule; at most, one may acknowledge that the metaphysical framework which some of them adopt is merely implicit.