Abstract

A central debate in bioethics is the nature of the early human embryo and its use in experimental or therapeutic research. Arguments proposed for the various biological marker events of "personhood" include: fertilization, implantation, formation of the primitive streak, the nervous system, the cerebral cortex, the brain--or several years after birth. ;This dissertation will analyze these arguments in depth by applying three criteria: the adequacy of the logic, the philosophical presuppositions in the definitions of a "human person", and the scientific data used to support these definitions as well as the distinctions between "non-persons" and "persons". ;I demonstrate that the conclusions of these arguments do not follow from their premises. Furthermore, within those premises are contained philosophical presuppositions in the definitions of a "human person". If a "person" is defined only in terms of a part of the whole human composite or subsistens , delayed hominization is argued for and supported by claims of various biological marker events during embryological development. If a "person" is defined as the whole human composite or subsistens, immediate hominization is argued for, rejecting such markers. Finally, most scientific data used to support these definitions of "human person" are inaccurate or irrelevant to the physiological or philosophical claims. ;I conclude that the arguments for the various biological "marker events" or personhood cannot be sustained logically, philosophically or scientifically, and result in various conceptual mind/body splits. I offer an argument for immediate hominization based on a revised Aristotelean-Thomistic definition of a "human person" and the correct science. This is the argument from potency in human actuality. My conclusion is that the original human zygote formed at syngamy is a living, individual, rational human being