Are embryonic stem cells potential babies?
If the human embryo has the potential to become a person and is supposedly morally important in virtue of that potential, then every other cell or organism with the same or a very similar potential must be assigned equal moral importance. This argument has sometimes been referred to as ‘the (absurd) extension argument’. The extension argument has been adduced to show that since oocytes and sperm put together in a petri dish also have the potential to develop into a person, they should be accorded a significant moral status too. Since the possibility of SCNT in mammals, some have also argued that each mammalian body cell has the potential to become a person. If these extension arguments are correct, then this has absurd implications for the potentiality argument. Our body would consist of millions of potential persons, and we would have to protect each one of them!
In what follows, I apply the extension argument to embryonic stem cells.    I argue that scientific experiments suggest that embryonic stem cells may have a potential that is similar enough to that of the embryo to cast doubt on the claim that embryonic stem cells have no significant moral status (assuming the potentiality argument is correct). The debate on the potentiality argument is a wide-ranging one. I restrict myself here to briefly discussing the most important arguments that have been adduced in the embryonic stem cell debate.
-  David B. Annis, ‘Abortion and the Potentiality Principle’, Southern Journal ofPhiloso-phy, 22 (1984), 155-63. Marco Stier and Bettina Schoene-Seifert, ‘The Argument fromPotentiality in the Embryo Protection Debate: Finally “Depotentialized”?’, American Journal of Bioethics, 13 (2013), 19-27.
-  L. W. Sumner, Abortion and Moral Theory (Princeton: Princeton University Press,1981). Helga Kuhse and Peter Singer, ‘The Moral Status of the Embryo’, in William A. W. Walters and Peter Singer (eds), Test-Tube Babies: A Guide to Moral Questions,Present Techniques, and Future Possibilities (Melbourne: Oxford University Press, 1982),57-63. Peter Singer and Karen Dawson, ‘IVF Technology and the Argument from Potential’, Philosophy and Public Affairs, 17 (1988), 90.
-  See e.g. Julian Savulescu, ‘Should we Clone Human Beings? Cloning as a Source ofTissue for Transplantation’, Journal of Medical Ethics, 25 (1999), 87-95. Alta R. Charo,‘Every Cell is Sacred’, in Paul Lauritzen (ed.), Cloning and the Future of Human EmbryoResearch (Oxford: Oxford University Press, 2001), 82-9. Gerard Magill and William B. Neaves, ‘Ontological and Ethical Implications of Direct Nuclear Reprogramming’,Kennedy Institute of Ethics Journal, 19 (2009), 23-32.
-  This section is partly based on Katrien Devolder and Christopher M. Ward, ‘Rescuing
-  Human Embryonic Stem Cell Research: The Possibility of Embryo Reconstitution’, Meta
-  philosophy, 28 (2007), 245-63, and Katrien Devolder, ‘To Be, or Not to Be?’, EMBO Reports,
-  (2009), 1285-7.