This belief that human life is valuable for its own sense and not as a means for something else is a stance advocated by hugely influential philosopher Immanuel Kant, who argues that people and foetuses have intrinsic value and not instrumental value - they cannot be disposed of for the benefit of others.
Philosophical claims to sanctity of life tend to base themselves upon the Natural Law argument put forward by the theologian Thomas Aquinas. He claimed that God as a Creator has devised a series of natural and observable moral principles. There is a fixed order and pattern in the universe, as fits with God's intention. Those who are rational and faithful would find five primary precepts; basic moral commands which God has embedded in nature: to preserve life, reproduce, educate, live in society, and worship God. The first of these to protect and preserve human life, is widely used to argue that killing is intrinsically wrong, and therefore, considering the foetus is regarded as a person, so is abortion intrinsically immoral.
Although the sanctity of life position almost invariably prohibits abortion in denominations such as Roman Catholicism, the doctrine of double effect could be used to justify abortion. If it is a secondary consequence of a primary intention, abortion can be justified. For example, the removal of the mother's womb in cancer treatment has the primary intention to save her life, but the secondary consequence of terminating the pregnancy. This is an attractive idea but the principle of double effect does not really permit abortion per se, but rather actions where the by-product may be an abortion if the action is seen as absolutely necessary.
One of the major theoreticians of preference utilitarianism for many decades, academic Jonathan Glover, has examined and subsequently critiqued the sanctity of life theory. In his book 'Causing Death and Saving Lives.' he describes the ethic as 'It is always morally evil to act intentionally and directly kill and innocent human being.' From that major premise it follows the traditional religious response, that since human embryos and foetuses are innocent human beings, to intentionally and directly kill them would be morally evil actions, regardless of any 'personhood' status, circumstances or intentions. Glover however doesn't hold these actions to be morally evil, he explains the major premise of the sanctity of life view as follows: 'It is always intrinsically wrong to destroy a life that is worth living.' Such a life would not be mere biological life, but rather as Glover describes it, the quality of life of one who consciously possesses preferences, plans, projects, desires, feelings, memories, a sense of identity etc. Since unborn children, as well as many mentally disabled or comatose adult human beings do not have this quality of life, they do not have a 'life that is worth living.' Therefore, they are 'non-persons', and their direct and intentional killing would not necessarily be a morally evil act. Many would disagree with this however like the philosopher Wittgenstein who argued that it implies the comparison of being alive to being dead: 'Death is not an event in life: we do not live to experience death.' Glover's views may seem extremely controversial, but it is reasonable to question what it is about life which is regarded as valuable, rather than singularly regarding all human life as sacred, as the religious treatment of the principle does.
Although the religious response of the sanctity of life principle prohibits abortion as the foetus is presumed to be a person, in the secular world a major issue lies in whether ethical status and moral worth can be extended to a premature being such as a foetus. Even if we accept the sanctity of life principle, should the sanctity of life of the foetus and the mother be considered with equal value? Thus the debate becomes one of personhood, one of the most predominant and difficult within the issue of abortion, which attempts to identify when a foetus becomes a fully fledges person, and thus when it is entitles to the religious concept of the sanctity of life.
A Christian response to the personhood debate is the idea of ensoulment, which states that personhood is achieved upon the implantation of a soul, which many religious believers maintain that the soul is implanted by God. In the 17th century, the Catholic church affirmed that ensoulment took place from the moment of conception. This is significant as if a soul is introduced at fertilisation, then a fertilised egg or at least an embryo, must be a human person. St Augustine believed that an early abortion was not murder because the soul of a foetus at an early stage is not present. Thomas Aquinas, Pope Innocent III and Pope Gregory XIV also believed that a foetus does not have a soul until 'quickening' and therefore early abortion was not murder, though was at a later stage. Aquinas, the main developer of Natural law, held that abortion was still wrong, even when it wasn't 'murder', regardless of when the soul entered the body.
A non-religious assessment of personhood is based on biological development and viability, of which, for instance, formation of the main organs or movement can be seen at the dividing line between potential and personhood. The problem with this approach of course is that every mother's experience of pregnancy is different, which is why Mary Ann Warren says 'birth, rather than some earlier point, marks the beginning of true moral status.' She rejects the idea that a foetus is a potential person: 'If a foetus is a potential person, then so is an unfertilised human ovum with enough viable spermatozoa to achieve fertilisation; yet few would seriously suggest that these living human entities should have full and equal moral status.' This is clearly as odds with the Roman Catholic position, which seems to suggest that a fertilised egg qualifies as a person. However, Warren's argument is vulnerable; surely a foetus that is capable of surviving outside of the womb is entitled to moral rights? A prematurely born baby is invariably less developed than a full-term baby still in the womb, yet there would be no question that the premature baby is a fully-fledged person. A different approach is taken by John Gallagher, who in 'Is the human embryo a person?' asks us to recognise that change is gradual, and there is no single point where we can confidently say 'now there is a person.' Similarly, there is a continuous development of an acorn into an oak tree, but an acorn is by no means an oak tree. Is it therefore possible to distinguish degrees of personhood? When Aristotle, who heavily influenced Aquinas, discusses what constitutes a person, he concluded with the proverb 'one swallow does not make a summer.' In his view, there is not one time or any individual characteristic which defines personhood, rather a person comprises a series of diverse experiences over a period of time. Personhood in this respect develops over time. We cannot therefore point to a moment when someone becomes a person. This may act as a support for those who deny the foetus personhood, yet a strict application of personhood to human beings is only applicable as an evaluation of their whole lives.
There lies a question within the personhood debate; are all human beings persons? Clearly within Christianity the answer would be yes, as all humans have received a soul at conception, which subsequently renders them a 'person.' However some moral theologians would question this, for instance a baby born without a brain mat be human as it is made of human tissue, but perhaps would not necessarily be regarded as a 'person.' Michael Tooley in his article 'Abortion and Infanticide' concludes that if a being lacks consciousness of self and has no rational feelings about its own future existence it is not a person at all. The obvious problem with this view is that such factors cannot be applied to babies immediately after birth, yet few would deny that full-term babies are clearly 'persons.'
Modern day Utilitarian Peter Singer maintains that whether or not a foetus is actually a person or not is irrelevant to the morality of abortion, and thus while a human foetus may possess sanctity of life or a soul this does not make abortion immoral. In his contribution to the person debate, Singer acknowledges that the foetus may be defined as 'an innocent human being' but denies the subsequent premise, that 'it is wrong to kill and innocent human being.' Essentially, the foetus is innocent and human, but is not a person of value or status. Not every human life can be seen as a person, since a person is defined as 'rational and self-conscious.' Humans who suffer from brain trauma may therefore cease to be a persons. The reverse is the case for the foetus, which is yet to become 'rational and self-conscious.' It is thus a less valuable form of life. Singer's theory can be seen as a helpful contribution as it offers clear criteria for defining as valuable life (personhood). Having said that, Singer has perhaps caused as many problems as he has solved, because his criteria for personhood are slow to develop and cannot easily be measured. As a society, we value the lives of those with limited mental faculties (the very young, the disabled, etc.) and yet these are the terms to which Singer limits the value of life.
Situation Ethics, considered by many to be a genuine attempt at modelling an ethic based on Jesus' teachings, offers a teleological way of approaching morality, while still upholding some of the fundamental Christian values i.e. 'love thy neighbour as thy self.' Situation Ethics views abortion as an evil act. Joseph Fletcher, its founder, stated that we should not get rid of rules as they are a useful guide in most situations. However, the only thing which is intrinsically good is love and so we may be required to 'push our principles aside and do the right thing.' The Church of England's position, that abortion is evil but may be the 'lesser of two evils.' is consistent with a situationist approach. If a woman has been raped, abortion may be an act of love and compassion. Fletcher's situation ethics maintains that you should act in the best interests of those affected, yet the real question is what counts as being in someone's best interests. This is where Christian ethics will include the idea that God created us, instructed us to reproduce and so on, and so seen in this light, Situation Ethics will originate from the belief that is generally in our best interests to create families, nurturing and educating our children. However, in exceptional circumstances, the situation might demand a different, loving response. Abortion would be an exception in extreme circumstances, as opposed to a method of birth control. For instance, in the case from 2009 of a 9 year old Brazilian girl who was raped and subsequently fell pregnant with twins, undoubtedly the compassionate and loving response would be to allow an abortion, as it is in the best interests for the girl, endangered by the pregnancy (sadly, following the choice to undergo an abortion, the girl, her entire family and the doctor who performed the abortion were excommunicated from their church in Brazil).
As with the case above then, abortion cannot be discussed in isolation from the psychological and social position of women. The woman has to go through the pain of labour and deal with the responsibility and care of the child, and so her decision should be paramount. Allowing abortion is seen by many feminists as a way of emancipating women from a form of slavery to their bodies, used by men to 'keep them in their place.' Thus feminist Beverly Harrison states 'the well being of the women and the value of her life plan should be recognised as of intrinsic value,' and goes on to say 'a good society is one that assures the existence of basic conditions needed to pursue an individual's own life plan,' the latter being a utilitarian argument. She does not, however, clearly state why one should not take the happiness of the embryo/foetus into the equation, as many may argue that no rights can over-ride those of another person (the foetus being a person). Conflicts can also arise with the happiness of the father, which along with the rights of the father, which along with the rest of society must be taken into account. It can also be noted that there are alternative ways of 'freeing' the woman, such as child care services to help her return to work.
In conclusion, the debate surrounding abortion is influenced heavily by both religious and ethical principles. This makes it hard to ever come to a definite conclusion about whether abortion is morally right or wrong. Since abortion affects the emotions as well as the mind, and as it involves considerations of the life and death, many people find that purely intellectual arguments about it are ultimately unfulfilling, and so perhaps the discussion of possible religious responses and the ethics that contradict or support then are necessary. As theologian Stanley Hauerwas articulates 'It may be that issues such as abortion are finally not susceptible to intellectual solution.'