In this paper, we will present a detailed systematic historical survey that shows the marginalization of metaphysics in current bioethical discussions. The marginalization we have in mind takes three forms. First, we will show that in some instances, metaphysical assumptions are entirely ignored in bioethical discussions. Second, we will show that in some instances, metaphysical assumptions are assumed but not recognized. Third, we will show that in some instances, metaphysical assumptions are smuggled into bioethical discussions without giving due credit. We will argue that the three instances pointed out here collectively establish the central claim we want to defend in this paper which is that metaphysics has not been given its proper place in contemporary bioethics. We will show why each one of these omissions poses a serious problems for a proper grasp of the ontology of personhood. We will argue why the arguments we put forth in this paper warrant our call why in bioethical discussions, philosophers and bioethicists must make a concerted effort to take metaphysics seriously. We will also show the way in which the marginalization of metaphysics is to blame for the superficial treatments of some of the central issues in bioethics such as abortion, infanticide, fetal status, embryonic status, embryonic stem cell and reproductive technology.