In this paper, we argue that issues in bioethics (e.g., abortion, fetal status, embryonic stem cell, reproductive technology, the human person at the end of life) necessarily raise fundamental metaphysical questions regarding the ontology of human personhood. By examining some of the representative views of contemporary philosophers (e.g., Daniel Dennett, Peter Singer), we will show in what way metaphysics has been ignored in contemporary bioethical discussions. We think that such indifference towards the centrality of metaphysics for bioethics is a serious mistake. We argue that sustained progress in dealing with complex and multi-faceted bioethical issues cannot be achieved without taking metaphysics as a proper starting point. The conception of metaphysics we want to defend in this paper is Aristotelian as opposed to Lockean and Humean. We will give some compelling reasons why metaphysics understood in its traditional, Aristotelian sense provides us with unique advantages to grapple with vexing bioethical issues. We will end our paper by considering three strong objections against the metaphysical view of human personhood we defend in this paper. The first objection comes from the domain of neuroscience; the second objection comes from the domain of artificial intelligence; and the third objection comes from the domain of human-machine interface. None of the objections we consider here would pose any serious threat to our claim regarding the centrality of metaphysics for bioethics on the one hand and the view of human personhood we defend on the basis of it on the other hand.