Peter Cross talks to clergyman John Polkinghorne about ethics

How do you deal with the provision of medical care in the context of limited resources? How do you calculate the cost of a heart transplant against the value of hip replacements? St Paul's Cathedral in London may seem an unlikely setting for a medical ethics lecture that purports to address these and other questions.

The lecture, "The Person, The Soul and Genetic Engineering" pulled together the wisdom and experience that John Polkinghorne gained in science and religion. Knowledge and expertise accumulated as a theoretical physicist, Cambridge professor, clergyman, past chairman of both the Human Genetics Commission and, for almost a decade, the BMA's Medical Ethics Committee.

The studentBMJ caught up with Polkinghorne just before his lecture, on his return from the Aztecs exhibition at the Royal Academy. The winner of the $1m (£600 000; a900 000) 2002 Templeton Religious Prize is uniquely placed to discuss some of the issues facing doctors, scientists, and indeed the lay public at the beginning of the 21st century.

"Science is a young person's game," Polkinghorne believes, "Particularly the sort of science I worked in, mathematical physics, where you need to be young and have mental flexibility. I enjoyed being a physicist. I regarded it as a Christian vocation, but it didn't seem to me a fruitful career forever. In middle age I decided to do something else." He became the dean and chaplain at one of the Cambridge colleges.

In this post he was phoned by the chief medical officer asking him to chair a committee revising the use of fetal material. The committee's report was adopted as government policy. He served on the Human Genetics Advisory Commission, then the Human Genetics Commission that replaced it: "As a clergyman I'm used to thinking about moral issues, and although I'm not a geneticist or a medical scientist in any conceivable sense, I know how scientists think, which enables me to play a bridging role."

"My main interests for the past 20 years has been how the scientific view of the world, which I take very seriously, and the religious view of the world, which I take with even greater seriousness, relate to each other. They're different perspectives on one reality. They are both concerned with a search for the truth but different aspects, so they have to fit in with each other but they can't tell each other what to think in their own domain."

Sir John believes that the principle of medical ethics is "you don't intervene on human beings except for their benefit and with their informed consent." He accepts, "There are problems with exactly how you apply that rule--for example, with children and in relation to the very early embryo. The first thing you have to decide is what stage is an embryo a human being. If it is then you can't kill it to take out its stem cells." The official position of the Roman Catholic Church is that an embryo is a full human being from the moment of conception. "I take a more developmental view of the human being," explains Sir John, "We grow into being human," he continues, "We acquire ourselves by development, and it seems to me that the fourteen day rule before the onset of structure within the embryo is a very cautious estimate of where to draw a line." He supports stem cell research where there are no alternatives but also agrees with laws which outlaw reproductive cloning.

Sir John finds genetics challenging in a number of ways. "The whole question of genetic engineering for cystic fibrosis doesn't raise any new problems for the public. If you could certainly engineer out a single mutation which, in Huntington's chorea would be a pretty worthwhile thing to do. But things like designer babies raises more serious issues--the great danger of codifying children."

He explains how genetic engineering law varies between countries. "We have quite strict legalisation: The Human Fertilisation Embryonic Act," he says, "In the States they have a very libertarian view. They have very weak sanctions and don't have public funding, but there is plenty of private funding for these things. In Germany, for example, the memories of the Nazi doctors are still heavily present, and they are very sensitive of any genetic modification."

He hopes to encourage public discussion and debate: "These things can't simply be left to the experts. They can't be judges in their own causes, carried away with the excitement of these developments. You can't have the discussion without the advice and assistance of these experts because only they know what can be done and the likely consequences of doing it. So there has to be a sort of public debate which involves the experts but doesn't simply delegate the responsibility to them. We need more of that in this country."

Although Sir John poses questions that he feels doctors are loath to discuss, he doesn't claim to have easy answers. "My general feeling about it is that you have to think about ethical dilemmas in a fairly general context but look at them in relation to particular issues. I suppose a way of approaching some sort of policy is if you improve somebody's life for 20 years or you keep somebody alive for three weeks before they get into a more advanced stage you should choose the first rather than the second. In extreme cases the choices are easy, but when the grey areas merge into each other it is more difficult to decide what to do."