Abstract
Protocols are investigating whether human stem cells can be coaxed into replacing tissue lost to disease or injury. What has been ethically controversial is if those stem cells are obtained by destroying human embryos. One recent proposal has been to alter a nucleus before transfer to a human oocyte (ANT) so that any resulting entity would not be able to develop into a fetus. The intent is that lacking a full complement of genes and potential, the resulting entity would not warrant protection as a fellow human being and so could be taken apart as a ready supply of embryo-type stem cells. The success of the proposal depends on the specific reasoning followed to establish the moral status of human embryos. This article describes how the Christian tradition thought about developing human life in the past and then traces more recent responses to the new challenge of technologies such as ANT that intervene in the earliest days of human development. Which arguments are persuasive for embryo status will largely determine whether ANT is morally acceptable.