Debate: Should doctors separate the Siamese twins?

Yes: Stephen Law

Yes: Stephen Law

You have been sent into space on a rescue mission. Two astronauts are trapped in different sections of a spaceship, their air running out. You reach the ship with minutes to spare, but the oxygen supplies to the two parts of the ship are connected in such a way that it is only possible to rescue one of the astronauts by shutting off the air supply to - thereby killing - the other. Do you allow both astronauts to die? Or do you save one astronaut by killing the other? Surely the right thing to do is to save one of the two astronauts.

We face a similar dilemma in the case of the Siamese twins, Jodie and Mary. We can save one of these two lives, but only by ending the other. Most people's moral intuitions supply the same verdict as in the astronaut case: the right thing to do is to save one of the two individuals, even if this does require that we kill the other.

A Christian might say "Thou shall not kill" is an absolute commandment. But there are exceptions, such as killing in self-defence. It would be extremely rigid to believe that God must want us to allow both Jodie and Mary to die - that their joint death is, in this sense, "God's will". Unfortunately, this is the view of the girls' parents. Yet it can surely be no more right to allow these parents to determine their children's fate than it would be to allow Jehovah's Witnesses to deny their child a life-saving blood transfusion.

Perhaps a more serious worry is that, by accepting that it is right to kill Mary to save Jodie, we open the door to disturbing medical decisions. Suppose a patient with terminal cancer possesses a healthy heart, a heart that, if transplanted into another, would save his life. If we do nothing, both will die within a few days. But we can save one by killing the other and transplanting his heart. But this kind of calculation seems morally abhorrent. That, one might argue, is why we should forbid the killing of Mary to save Jodie.

But there are times when it is clearly wrong not to kill to save a life. Our fears should not over-ride our strong moral intuition.

* Dr Stephen Law is author of 'The Philosophy Files' and lectures in philosophy at Heythrop College, University of London.

No: Richard Nicholson

The choice for the Court of Appeal in deciding the fate of the Siamese twins, Jodie and Mary, is stark. Order the twins' surgical separation and Mary, according to the evidence so far, will die at once, while Jodie is likely to survive but possibly with major handicaps. Do not order separation, respecting the parents' refusal of consent to it because it is not God's will, and both twins die within weeks or a few months.

The issue of what rights accrue to each part of Siamese twins has never been addressed in law. Given the existence of two recognisably human beings, one cannot argue coherently that they do not both have rights. If both have rights, the two most fundamental rights - to life and to justice - must be respected. So both Jodie and Mary have a right to life and a right to justice, or in other words, to be treated equitably. Surgical separation would deny Mary both rights.

What has so far held sway among the professionals, however, is a crude utilitarian approach. Any life is better than no life, goes the argument, so separation must be the right answer. But a sophisticated utilitarian calculus would require many more factors to be taken into account, not least the danger to future infants if it is established that you may kill one baby to save another. It would also examine what quality of life Jodie might have, and the effect of an adverse decision on the parents, their marriage, their family and their community.

There is a curious irony in the Manchester doctors, and indeed Mr Justice Johnson in the High Court, being unable to respect the parents' decision, based as it is on a firm belief in the commandment "'Thou shalt not kill". First we have scientists proclaiming that there is no God as if they could prove it, whereas their disbelief is as much an article of faith as Christian belief in God. This case shows clearly how, in the absence of a belief in God, respect for physical existence is diminished. One opts for whatever course of action will give the most physical existence, even if one has to destroy another human being in the process.

* Dr Richard Nicholson is editor of the 'Bulletin of Medical Ethics'