Experimentation on embryos, they thought, should be impermissible after the fourteenth day. The reasons were well summarized in the House of Commons by Kenneth Clarke when Secretary of State for Health:
A cell that will become a human being -an embryo or conceptus -will do so within fourteen days. If it is not implanted within fourteen days it will never have a birth . . . . The basis for the fourteen-day limit was that it related to the stage of implementation which I have just described, and to the stage at which it is still uncertain whether an embryo will divide into one or more individuals, and thus up to the stage before true individual development has begun. Up to fourteen days that embryo could become one person, two people, or even more.
Jones disagrees with this ethical reasoning. He defends the view, currently the dominant Catholic one, that individual human life begins at conception. An embryo, from the first moment of its existence, has the potential to become a rational human being, and therefore should be allotted full human rights. To be sure, an embryo cannot think or reason or exhibit any of the other activities that define rationality; but nor can a newborn baby. The protection that we afford to infants shows that we accept that it is potentiality, rather than actuality, that determines the conferment of human rights.
In adopting this stance Jones is taking issue with some of his fellow Catholics, such as Elizabeth Anscombe and Norman N. Ford, who argue, on the same basis as Warnock and Clarke, that individual life cannot begin at a stage when an embryo may well split into a pair of twins. Jones's response to this is that an embryo is an individual human being which has a certain power -that of twinning -that is lost in later life. But to count embryos is not the same as to count human beings; and in the case of twinning there will be two different human individuals, each of whom will be able to trace their life story back to the same embryo, but neither of whom will be the same individual as that embryo.
In arguing for conception as the moment of origin, Jones rightly stresses that before fertilization we have two entities (two different gametes) and after it we have a single one (one zygote). A moment at which one entity (a single embryo) splits into two entities (two identical twins) is surely equally entitled to be regarded as a defining moment. If Jones defends his position by urging that in the vast majority of cases twinning does not actually take place, he is surely forgetting his own correct emphasis on the ethical importance of potentiality. It is the potentiality of twinning, not its actuality, that gives reason for doubting that an early embryo is an individual human being.
David Albert Jones is a skilled and fair-minded advocate for the position that individual life begins at conception. However, in my view, his arguments fail to weaken the case for placing the origin of personhood somewhere around the fourteenth day of pregnancy. But there are two sides to the reasoning that leads to that conclusion. If the course of development of the embryo gives good reason to believe that before the fourteenth day it is not an individual human being, it gives equally good reason to believe that after that time it is an individual human being. If so, then late abortion is indeed homicide -and abortion becomes "late" at an earlier date than was ever dreamt of by Aquinas.
Aiming To Kill: The ethics of suicide and euthanasia is concerned not with the moment at which human life begins, but the moment at which it ends, and with the ethical and legal problems that surround the hastening of that moment. The book defends the legal prohibition of euthanasia and assisted suicide, and argues that there should be no relaxation of traditional attitudes. Nigel Biggar begins by maintaining that the special value of a human life derives from a call of God to each individual to play an inimitable part in promoting the world's welfare. From this explicitly religious starting point the argument is developed in ways which are of interest also to those who take a more secular view of the value of life.
The major part of the book is devoted to distinguishing cases where it is, and where it is not, permissible to cause the death of oneself or of another.
