We could start by asking certain questions: Are embryonic stem cells stable enough for safe transplantation? Isn’t it wiser for investors to prefer adult stem cell research? Etc. There is, however, a more fundamental question to be answered first – what is the moral status of the human embryo?
Some would argue that human embryos aren’t persons and are therefore of a lower moral status, one which doesn’t confer the right to life. Surely this is just playing with words: those to be protected are given a certain designation (‘person’), which is then denied to some members of the group on the grounds that they don’t seem to be worth protecting or can’t defend themselves. We have to look beyond words to what makes us special. The main thing which distinguishes human beings is our rationality. That rationality is inherent in everyone, even though, like any faculty, it is not exercised by all people, all the time. Human embryos share our human nature, and have the capacity for rationality, even if they are, for a time, unable to exercise that capacity. Embryos are just as human whether their physical origin is through ordinary fertilisation, spontaneous twinning, or, as experience has shown, artificial processes.
Attempts to relegate certain human beings (often on racial or ethnic lines) to a status of non-personhood have led to some of the most heinous abuses and extensive massacres in modern history. All human beings are equal in nature, and therefore it is not for one group of human beings to decide that another group of human beings are of lower moral status i.e. are not persons. One might argue that there is even less excuse in this case, since each of us is directly connected with the class of human beings concerned - we were all embryos once.
The person we are now is the same being as the embryo we once were. This cannot be said of the sperm or the egg, because alone they couldn't have developed into a human being. A sperm and an egg remain a ‘potential person’ (loosely speaking), a purely conjectural non-existence, until fertilisation, but then become a person with great potential. Personhood is in the embryo’s nature - if the embryo wasn’t already a person, it couldn’t become a person. Otherwise personhood would be a faculty, like consciousness, that can come and go. Anyone under general anaesthesia isn’t a person, and then becomes a person again when they come to!
These arguments don’t require religious beliefs. Immanuel Kant, for example, believed the existence of rational beings (i.e. humans) has an absolute worth. Humans are therefore ends in themselves and should therefore never be used as a means to an end. Still, almost all religions hold that ‘man is made in the image and likeness of God’ and/or that ‘human life is sacred’. These religious or metaphysical beliefs remain widely held today and are probably the majority opinion of human society throughout history. The international community has recognised ‘the sanctity of human life’ in secular form: the 1948 Universal Declaration of Human Rights not only states that “everyone has the right to life” (article 3) but that “everyone has the right to recognition everywhere as a person before the law” (article 6).
Have decades of embryo experimentation discovered much more than new ways of destroying embryos? Isn’t the government’s draft Human Tissue and Embryos Bill another step along the road to a eugenic society, in which those with serious medical conditions are deemed unworthy of life? The fundamental question remains unanswered (indeed, unaddressed) – what is the moral status of the embryo?