The comforting certainties of what is natural are constantly being eroded. But we must keep our heads, argues Mary Warnock, and remember that as the brightest animal humans have a duty to modify nature if good will come and to use restraint if not

The word interference is, on the whole, pejorative: those who argue that the new biotechnology and its possible applications constitute an interference with nature certainly understand it to be so.

But when Prince Charles, in his 2000 Reith Lecture, besought biologists to learn more about nature, if they wanted, but not to seek to change it, his father and sister were quick to point out that men had been changing nature - interfering with it - since human history began. And it is true that had they not interfered, we would be living a wilderness life, none of our sophisticated pleasures and pursuits even conceivable.

Although this is well understood (and certainly, in fact, by Prince Charles, who was really pleading not for non-intervention, but for the use of "tried and tested" techniques of agriculture), there is a persistent appeal in the cry that biological science has now gone too far, and that we ought to stop interfering and let nature take its course.

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Our idea of what counts as natural is complex and has changed through the centuries. At present, it has at least two crucial components, the romantic and the Darwinian.

French philosopher Jean-Jacques Rousseau began his novel Emile with the statement that everything is good as it comes from the hands of the author of nature, and everything degenerates in the hands of man. He was talking specifically about children, but the proposition was also meant to be general. From then on, nature began to be thought of as an intrinsic value, opposed to the values of society, thus forming a crucial part of the romantic ideal.

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In the 18th century, until Rousseau, it was thought that nature existed to be improved upon. Wild, untamed nature was simply less agreeable than nature cultivated. The new spirit of Romanticism, on the contrary, in Britain and all over Europe, demanded that the natural world of wilderness be regarded as awe-inspiring, a source from which men could draw understanding of their own being, and from which they would receive the most sublime aesthetic intuitions. The immutability and grandeur of nature, as well as its freedom from corruption, had the power to return men to their true identity, allowing them to see where they really belonged.

But alongside this new sensibility the thought that nature was the proper object of scientific study was already developing. Carolus Linnaeus, the Swedish botanist who died in 1778, had already established the binomial system of biological nomenclature that is the basis of modern classification. And besides professionals, there were innumerable amateur diarists and watchers of nature, among them Gilbert White, whose Natural History of Selborne was read with delight by Charles Darwin as a boy. The idea was gradually taking root that, just as Newtonian physics provided laws governing the behaviour of all matter, so there were historical laws of development equally ineluctable in the biological world. The publication, in 1859, of Charles Darwin's On The Origin of Species provided an explanation of how species evolved, by competition for life in a world of scarcity and the survival of the fittest. When Darwin published The Descent of Man 12 years later the foundation was laid for a concept of human nature that, more or less, is with us still.

However, Darwin's theory of evolution was still less than explanatory because it was not clear to him how the variations within a species that led some to survive, others to fail, came about. For this, we had to wait for the birth of genetics in the 20th century. So now we are Darwinians, but instead of concentrating on the macro scene - the development and behaviour of different species - our attention is fixed on the micro - the gene within, which determines the mechanism for this development.

Human nature is now tied up with nature as a whole, not simply by the bonds of romantic sensibility, nor by the human desire to observe and understand the natural world, but by the laws of biological science. Human beings are thought to be determined by their genes. But genes may be shared across the natural world, bringing all creatures, plants, fruit flies, men and women into a kind of universal cousinhood. So one may ask whether those who object to interfering with nature - especially those who object to genetic intervention in human subjects - are simply expressing their outrage at the diminution of the status of man, his now unspecial place in the universe. This would bring the objectors into line with the church in the battles that raged in the 20th century between T. H. Huxley, "Darwin's Bulldog", and the theologians over the theory of evolution.

I do not think this is the explanation. That argument was primarily theological, and although Prince Charles expressed his view that biologists, in manipulating genes, were trespassing on areas "which belonged to God and God alone", this did not mean that he was talking about theology. His argument could have been couched in terms of nature and nature alone without making any substantial difference. His words were metaphorical. The argument has moved on; for those who believe that interference with nature is wrong accept most of Darwin's premises. They are not, therefore, re-enacting the passionate disputes of earlier times. Why, then, the emotive word "interference"?

Those who use such terms feel both aspects of our idea of nature to be under threat. On the one hand, the romantic or aesthetic idea of nature is undermined by the threat of genetic manipulation. Nature in the Rousseauesque or Wordsworthian sense is untouched by human hand. It is wild in the sense that it is partly random, beyond total control. If crops are to be genetically engineered, animals caused to produce milk at all times, fruit made to last throughout the seasons, babies programmed to have the features their parents desire, then the element of astonishment (or disappointment) that is part of our reaction to nature will be eliminated. Our lives will themselves become unnatural.

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Equally, our Darwinian ideas seem themselves under threat. Jonathan Porritt, former director of Friends of the Earth, in Playing Safe wrote:

"The hard lines between different organisms and species are beginning to melt away. We can now pick and choose individual genes from one organism to introduce into a totally different and unrelated organism, crossing all biological boundaries in combinations that nature never could and never would bring together."

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The laws of biological nature themselves, which we have accepted since Darwin, seem to be eroded. In a world where, we are constantly told, there are no universal laws of morality, how much the more terrible to be deprived of the certainties of natural law.

However, it is important to keep our heads, and not be swept away by the rhetoric of "the natural". We are indeed part of the natural world, though being brighter and more far-seeing than other animals, we have particular duties towards it, and towards our fellow humans. We should not lump things together in damaging dichotomies - the genetically modified or the organic, babies born incurably sick or designer babies. We must allow research to go on so that the techniques of genetic modification can be applied where good will come, while keeping our eyes open for unforeseen damaging consequences, including the enrichment of quacks or exploitative companies.

If, for instance, it can be shown that the genetic modification of rice to make it more tolerant of adverse weather conditions would make a great difference to the level of nutrition in countries where rice is the basis of the diet, then common humanity demands that such rice should be made available.

If it can be shown that stem-cell transplant can effectively restore someone's damaged brain, then the common humanitarian concerns always at the heart of medicine should allow such treatment to be carried out. Genetic modification will not be all good or all bad, just as surgery or the breeding of specialist dogs and horses is not all good or all bad.

For my own part, I can think of only one development that I would consider certainly wrong. Suppose that one day someone argued that if specific cells in the body could be renewed, then perhaps all cells could be, so that death itself could be eliminated or indefinitely postponed. I would regard this as unimaginably wrong. All art, all religion and all morality is built against the background of the fragility of life. Life is essentially ephemeral. But perhaps this is only an ultimate appeal to the rhetoric of Nature.

Mary Warnock is a moral philosopher, former mistress of Girton College, Cambridge, and was chair of the Committee of Inquiry into Human Fertilisation and Embryology from 1982-1984.

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