The moral status of the human embryo is central to contemporary debates on the ethics of cloning, embryo research, stem cell research, genetic engineering, assisted reproduction, preimplantation diagnosis, genetic screening, post-coital contraception and the production of chimaeras and 'non-organismal entities'.
Although the language predominantly used in the media is that which denigrates the embryo's moral status  the issue is still vigorously debated in both medical  and Christian literature.[3,4] Christians have disagreed on the issue throughout history, and because of its practical implications for medical practice the debate amongst Christian doctors continues.[6,7,8]
A CMF abortion survey published in 1996 revealed a variety of views among the 2,580 doctors and 348 student members who responded. 36% of doctors and 68% of students believed human life had 'full value' from the time of fertilisation (by eight weeks' gestation these figures had risen to 85% and 92% respectively). However, the way these views were expressed in practice seemed inconsistent; only 20% of doctors and 50% of students said they would refuse to use methods of contraception that might act by preventing implantation. It is essential for medical students to decide where they stand on the issue as it will have a huge bearing on their later medical practice.
Several prominent commentators have justified infanticide on the grounds that handicapped neonates are not fully human; amongst them eugenicist Margaret Sanger, bioethicist Michael Tooley, and Nobel laureates for the discovery of DNA, James Watson and Francis Crick. Most would regard such views as extreme, although the view that the fetus has a lower moral status has become increasingly mainstream since the legalisation of abortion by the 1973 Roe vs Wade judgment in the US and the 1967 Abortion Act in the UK. The lowered status of the human embryo was given statutory force in the 1990 Human Fertilisation and Embryology Act, which allows embryo freezing, experimentation and disposal up until 14 days after fertilisation.
A philosophical defence
Biologically the human embryo is undoubtedly human; it has human chromosomes derived from human gametes. It is also undoubtedly alive – a new active individual human organism from the moment of fertilisation exhibiting respiration, growth, reproduction, excretion and nutrition. Human development is a continuous process beginning with fertilisation; essentially the only differences between zygote and full term baby being nutrition and time.
Rather than speaking of it as 'a potential human being' it therefore makes more sense to speak of it as 'a human being with potential', 'a human being in an early stage of development' or 'a potential baby or adult'.
A philosophical defence of the human embryo is based on the principle that every human being has a right to life and human beings must not be discriminated against on the basis of age, sex, race, disability or any other biological characteristic. This right to life is upheld in historical secular ethical declarations. The UN Declaration of Human Rights (1948) asserts that 'everyone has the right to life', the UN Declaration of the Rights of the Child (1959) states that the child deserves 'legal protection before as well as after birth' and the European Convention on Human Rights, now embodied in UK law as the 1998 Human Rights Act  defends the 'right to life'. The right to life includes the right not to be killed.
The right is also enshrined in medical ethical declarations historically adopted by the World Medical Association, which enshrined the provisions of the Hippocratic Oath in a secular context. The Declaration of Geneva (1948) states 'I will maintain the utmost respect for human life from the time of conception even against threat', whilst the International Code of Medical Ethics (1949) affirms that 'a doctor must always bear in mind the obligation of preserving human life from conception'.
To argue that embryos can be killed in circumstances where older human beings cannot be is therefore to employ a type of ageism, what one author has called natalism (the superiority of the born over the unborn), 'the chief atrocity of our time'.
A biblical defence
A biblical defence of the human embryo is based on the idea that human beings are made in the image of God  and belong to God  and therefore should not be killed  except in very special circumstances. God's image is endowed by grace; conferred from outside, and therefore not contingent on any intrinsic properties the embryo may or may not possess. The sixth commandment, 'you shall not murder' specifically proscribes 'the intentional killing of an innocent human being'  a point argued by the author in more detail elsewhere.
In other words the Bible authorises only the killing of the guilty. The shedding of 'innocent' blood is uniformly condemned throughout Scripture. We must not become confused here with legal, psychological or social definitions of murder. The Bible does not support the conclusions of others that murder is 'the killing of a human being unlawfully with malice aforethought', killing with 'a feeling of ill-will' [29,30] or 'illegal killing inimical to the community'. It is rather 'the intentional killing of an innocent human being'.
That human beings include embryos is affirmed by many specific biblical references to life before birth. Psalm 139:13-16 affirms God's creation of, and communion with, the embryo-fetus in the womb as well as implying continuity between life before and after birth. God calls Isaiah and Jeremiah before birth  and forms Job 'in the womb' as well as bringing him out of it. Many other references to life before birth in the Bible reinforce these principles  and there are over 60 references that make reference to 'conception' explicitly, implying that this is when a new life begins. Most fundamentally, human nature is identical to the human nature of Christ who 'became flesh' at a moment of time, at conception, and who 'was made like us in every way'. In other words, if Christ's human life began as an embryo then so did ours.
Also fundamental to the Bible's teaching on the status of human life is the principle that God himself is completely just and impartial. This is consistent with New Testament warnings about not discriminating on the basis of wealth, sex, race, social standing, and age  and Old Testament respect and protection for easily exploited groups such as the poor, widows and orphans, aliens, the handicapped, slaves and the elderly.
It follows that devaluing any human life, let alone vulnerable human life, is inconsistent with God's justice. The heart of Christian ethical teaching is that we must love as Christ himself loved, that the strong should lay down their lives for the weak. To suggest that the weak may be sacrificed in the interests of the strong is not biblical morality.
Secular philosophers and biologists have employed a variety of arguments to support the view that embryos are not 'fully human'.
1. The embryo lacks rationality or capacity for relationship
This position argues that embryos are therefore not 'persons' to whom we owe responsibility.[42,43] This has been popularised by Singer, Edwards  and Lockwood  and was the thinking behind the Warnock Committee's recommendation of no embryo research beyond 14 days, on the basis that the neural crests first form ten days after fertilisation. Others have suggested that organogenesis (eight weeks) breathing movements (twelve weeks), 'quickening' (20 weeks), or even the first breath of air should be the end point. This view, in presupposing that human worth is contingent on the degree of neurological development, simply introduces another form of discrimination - neuralism - where some human beings are discriminated against on the basis of the amount of higher neural function they exhibit. It further assumes that a clear line can be drawn, whereas in fact the development of the nervous system is a continuous rather than a step-wise process, making any chosen division between human and non-human purely arbitrary. Furthermore it assumes that human worth can be reduced to an evaluation of functional attributes. The value of human beings does not consist in their capacities or attributes but in the fact that they are human. Singer argues that to respect all human beings simply because they are human is speciesist. We don't employ the same criteria with animals. But this simply brings us back to the question of whether human value is achieved or endowed. The former option places us on a dangerous slippery slope, where everyone will draw the line at a different place depending on his or her own arbitrary criteria. It is far less dangerous, and more humane, to respect all human life equally.
2. Many embryos die anyway
A second approach is to lower the value of embryos on the basis of their high mortality. By some estimates 40-70% don't reach maturity. But does this indicate that they can be regarded as more expendable? Is the value of human beings contingent on their survival rates? We don't say that Sudanese refugees or people living in regions prone to flooding have less value simply because they have a high mortality. If survival rates at any stage of development are low this does not justify us actively ending a human life in other contexts. The general strategy of medicine is rather to save and preserve human life. The claimed figure of 40-70% may well be an overestimate anyway. No-one really knows how many early embryos die as there is no widely-used biochemical marker for fertilisation, as opposed to implantation.
3. Many embryos are abnormal
Embryos that do spontaneously abort have a high incidence of genetic (particularly chromosomal) abnormality. But to lower their status for this reason assumes that human worth is contingent on degree of disability. We would not argue in other contexts that the value of human life was contingent on its level of normality; far less that abnormality justified killing. To do so moves us onto the same ground occupied by the intellectual progenitors of the Holocaust, Binding and Hoche, who coined the term 'life unworthy of life' - ballastexistenzen (literally 'human ballast'), to describe people suffering from various forms of disability. Human embryos with disability are just very young human beings with special needs.
4. Sperm and ova are just as human
Why should we deeply respect embryos when we don't treat sperm and ova, which are equally both human and alive, in the same way? This view was the theme of the satirical song 'Every sperm is sacred' that parodied the Catholic view of live before birth in the Monty Python film The Meaning of Life. But in fact an embryo is a genetically distinct living human organism in itself, already with a unique genotype and the inherent ability to grow into an adult. Sperm and ova are not. They are simply haploid cells, part of the body of another human being, but with no inherent capacity, in themselves, to grow and divide.
5. Implantation is the key
If we regard conception as a process, which is not complete until implantation, why is it wrong to interrupt this process before its completion? The embryo up until this time is simply free floating. But we could equally argue that organogenesis, or the development of the nervous system, or indeed life itself equally a process. And yet we wouldn't use the same argument to justify ending them before their completion. The point is that an individual human life begins at fertilisation. It is better not to intervene in any new life process that has already commenced; and to argue that a free-floating embryo is not worthy of respect is to say that human worth is contingent upon its place of residence, a non-morally relevant characteristic.
6. Other products of conception are not human
In order to establish a case for some embryo destruction extreme cases are often cited; most typically the hydatidiform mole or the choriocarcinoma, neoplastic and life threatening products of conception. However we now know that a hydatidiform mole results not from the union of male and female gametes but rather from two male gametes. It is not technically a 'product of conception' at all.
7. Much of the embryo is redundant
Not all tissue derived from the fertilised egg ends up in the embryo (ie some becomes yolk sac etc). Does this not therefore imply that the embryo is something different from a human being? It is true that the early embryo contains tissue that does not become part of the fetus but this makes the embryo something more than a human being rather than something less. The cells that are destined to produce the adult are contained within it. Interfering with an embryo thus risks damage to the embryo itself, or alternatively to part of its support mechanism.
8. Some embryos twin
Monozygotic twins make up three to four of every 1,000 births and usually divide at the embryo stage between three and 14 days after fertilisation. It is argued that each twinned individual therefore has its origin at the stage of division rather than fertilisation and that therefore by implication all individuals have their origins after fertilisation. Admittedly it is difficult to conceive of two individuals inhabiting one body; but it does not follow that what we find difficult to conceive of cannot therefore be the case. We would maintain that Siamese twins (although one body) are two persons. The two embryos that result from twinning had their origin in the same embryo. We have already conceded that the embryo is more, not less, than a single human life. The fact that we do not fully understand the mystery of twinning does not mean that we should not show respect to the embryo prior to twinning taking place. Killing an embryo at that stage undoubtedly kills a living organism and prevents the development of two individuals.
9. We already treat embryos as less than human
Finally it is submitted that we do not recognise embryos as human because we have already accepted technology like post-coital contraception, which we know endangers their survival. But the implication here is that our beliefs somehow determine the way things actually are. The laws about embryo research in Britain are among the most liberal in the world and run counter to traditionally accepted ethical codes. Rather than letting our practice determine our principles, should not we be letting our principles determine our practice?
Rather than making reality subject to our prior beliefs, it is surely better to let reality shape our beliefs. The value of a human being does not depend on how others may value it or miss it when it is gone. It has value simply by virtue of being human.
Some Christians employ the above 'secular' arguments to justify embryo experimentation or post-coital contraception,[53,54] but also have biblical arguments of their own.
1. The Bible devalues embryos
First it is argued that the Bible itself teaches by implication that embryos are less valuable than children or adults on the basis of an interpretation of Exodus 21:22-25. The author has argued this more fully than space permits here elsewhere.
In short, the verses have been misinterpreted in two ways. First, the Authorised Version and Revised Standard Version translations of the original Hebrew imply different punishments for the accidental killing of a mother (death penalty) and her unborn child (a fine). Some authors have concluded from this that God himself apportions different values to mother and fetus. The New International Version translation, by contrast, implies that the death penalty was for fetal or maternal death, and the fine was for injury without fetal or maternal death. This latter interpretation is now accepted as the correct one by most contemporary scholars.[56,57,58,59] Even had the former interpretation been correct, the fact is that the text deals with accidental, not intentional, killing. It's also noteworthy that killing slaves was not a capital offence in the Old Testament despite the fact that slaves were as important to God as anyone else! We cannot therefore infer from this text that the early fetus or embryo is worth less in the eyes of God; or that it can be justifiably killed.
Second, the medieval church based their interpretation of Exodus 21 on the Septuagint (Greek Old Testament) rather than the original Hebrew. The Septuagint translation states that the fine or death penalty was determined by whether or not the (dead) fetus was 'formed' or 'unformed'. The Hebrew says nothing of the sort, but the error led astray even Augustine and Aquinas before it was later recognised.
Despite these misinterpretations, there has been 'a tradition of concern and respect for the human embryo throughout church history', with its expulsion from the womb, other than to save the mother's life, never being sanctioned, until the adoption of more liberal views in the late 20th century. There is nothing else in Scripture that even remotely suggests that the unborn child or embryo is anything other than a human person deserving of the utmost respect from the moment of conception.
2. The image of God was lost at the fall
This view was taken by Athanasius and accepted in part by Luther and Calvin. This has led some authors to suggest that human beings have lost the right to protection along with the image, although Luther and Calvin never suggested this and Scripture itself teaches that the death penalty for murder (killing an innocent human being) was instituted after the Fall and was based on the fact that man was made in God's image. Even if we were to accept that the image of God was damaged in the Fall, this still gives us no basis for killing innocent human beings in any circumstance at all, and even if it did it would apply equally to all human beings and could not be used to argue for a relative diminution of the embryo's moral status.
3. Embryos don't have souls
A third line of argument is to justify embryo disposal on the grounds that embryos don't have souls, but rather that the soul enters the body at a later point. This has been argued from Exodus 21 (refuted above) and also from Hebrews 10:5, which speaks prophetically of Christ in saying 'a body you prepared for me'. However the danger in generalising from the specific case of Christ is that whilst he was 'pre-existent', ordinary human beings are not. It is one thing to say that believers were 'chosen in (Christ) before the world was made', but this does not mean that they existed before the time of their conceptions. Regardless, as argued previously, the natural reading of the biblical account of Christ's incarnation is that this occurred at conception, and surely in the case of any doubt about when a new human being comes into existence, the benefit of that doubt should be given to the embryo. The idea that human beings can be divided into body and soul is based on the ancient Greek idea of body and soul being separate entities; a notion which finds no support in Scripture. While it is true that all human beings survive death and face judgment, and that there is some debate about the nature of the 'intermediate state', the destiny of redeemed human beings is to be clothed in a 'resurrection body', like that of Christ after his resurrection. Redeemed human beings are not disembodied spirits, either before conception  or in eternity. This issue has been dealt with in more detail elsewhere. The biblical word 'soul', rather than referring to a disembodied spirit, actually includes the body. We have bodies and are souls, rather than the other way round.
I have argued on the basis of both a rights-based philosophical argument, and on the basis of a biblical view of anthropology and morality that human life begins at fertilisation and should be accorded the utmost respect from that point in time. I have also examined and refuted the major philosophical and Christian objections to this view. This has profound implications for the way we should treat human embryos both in research and in clinical medicine.