Because researchers can't always provide definitive answers, making them appear vague and untrustworthy, but don't despair, says John Sulston

Before starting this piece, I had been preparing a review for a candidate for a scientific prize. It is a pleasant occupation. To sit in the library pulling journals off the shelf, following references from one to another, often chasing down an alley of thought that has nothing to do with the task at hand. And at the end of the morning a whole area of discovery is laid out on the desk.

I can get at things for myself, nobody tells me what to think, and if something doesn't make sense I can dig deeper. Other scientists are talking to me through these publications; I don't have to believe anyone in particular, but collectively I can trust them. Maybe someone has exaggerated or made a mistake, but most problems are soon caught, and I can check one claim against another - a process that is becoming more and more convenient with the advent of electronic records. If stuck, I can phone a friend. I can even, in principle, do practical checks of my own; although in practice this would take too much time for a mere review, it's possible to set off on a quest in this way. The one necessary axiom is that we are all talking about the same external reality, but more of that in a moment.

So how can there possibly not be trust in such a system, where anyone, no matter how junior, can challenge the received wisdom, where, indeed, we often advance by picking holes in someone else's work. What can go wrong with the public perception of such an open endeavour?

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One of the problems is that the questions asked of science aren't necessarily those that it can answer, at least not right away. We all know the story of the man who was found searching for his keys under a streetlight; he had actually lost them farther along the road, but it was dark there and he preferred to search in the light. Crazy, but in research it makes sense to proceed in this way, because we aren't looking for one set of keys but the keys to everything. And as we find keys they turn on lights farther up the road, rather like one of those computer adventure games, so eventually we find the real object of the hunt along with all manner of discoveries that we hadn't dreamt of.

For example, it isn't yet sensible to ask of science, "what is the purpose of human existence?". More sensible, it seems, is to ask, "what is the cause of Aids?" or "is human activity causing global warming?". Over time, science is the best way of getting clear answers to these two questions and, indeed, in both cases there is already a strong consensus as to the correct answers. However, both questions are complex, in that direct experiments are unethical or impossible, so we have to rely on indirect experiments and calculations. The result is that - given the essential anarchy of science just described - you can always find scientists who disagree with the majority views, which in these cases are "HIV" and "Yes".

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These particular minorities have been gleefully seized on by President Thabo Mbeki and President George W. Bush respectively for their own political ends.

The consequence is that many people are left with the impression that science is pretty vague about everything. An extreme view, which is fashionable, is that the discoveries of science are socially determined and no more objective than, for example, literary criticism. This perspective, which has many earlier incarnations, results from looking only at the current edge of discovery. A moment's thought shows that for a very long time science has not only been correct in its overall conclusions but that it has also been humanity's greatest cultural driver. There aren't many earth-centrists left, but 400 years ago, those who dared to show that our planet was not at the heart of the universe were imprisoned and tortured. A larger number of people, including, sadly, a substantial proportion of the richest country's citizens, are unwilling to accept the overwhelming evidence for the 150-year-old theory of evolution, but that will change as the facts continue to come in. Both these waves of discovery have had profound cultural consequences. We continue from era to era of growing understanding, always with uncertainty at the leading edge. Maybe we shall eventually reach a point where the scientific approach can take us no further, though that time is a long way off.

But the central problem, and a continuing one despite all our efforts, is poor communication all round. This has led to a two-way erosion of trust between scientists and the public. Public perceptions of scientists cite career ambition and corporate or political agendas as reasons for distrust.

Surveys show more trust of those who work in universities than of those who work for the Government or industry. But in general, there has been a decline in automatic acceptance of what scientists have to say.

Scientists in turn feel abused by these sentiments. Mostly they are doing their best to do good, and they feel that their treatment is unjust. For some there is despair that, despite great efforts at communication, the talking hasn't helped. Crop scientists feel this acutely. They, like many others, feel a rise in irrationality that undercuts attempts at meaningful discussion. Finally, many scientists at one time or another feel that the media distorts their statements. Criticisms on both sides are justified for some people some of the time and need to be looked at in a little more detail.

First of all, it must be said that we are all the public. Every scientist gets information about fields of research that are distant from their own in much the same way as anyone else - through commentaries of various kinds, including the media. Scientists share a sense of an objective reality and a view of what constitutes evidence. But for knowledge of what is actually happening in those other fields they do not have a privileged position. In some sense, everyone is a scientist (science, in one useful definition, is simply "applied common sense"). However, the distinctive feature of professionals is that they have spent a great deal of time learning about a particular area and so are expert in it. As in any profession, a combination of such painstaking effort and natural aptitude can create a daunting gulf between the expert and the rest.

Personal ambition is one of the two great characteristics of science, along with its alter ego, communal sharing. Without the bloody-minded persistence of individuals we would discover nothing. There are always lots of good reasons not to do a given experiment. It is said with some truth that progress is made by those who haven't read the literature and so don't know that their idea won't work. The biochemist Erwin Chargaff justly accused Francis Crick and James Watson of practising biochemistry without a licence. In turn, Crick kept a large notice over his desk that stated:

"Reading rots the mind." Anyway, at some point everyone has to get out of the library and do something. Being a great ditherer, I would frequently start an experiment far too late in the afternoon simply because I'd spent the whole day pondering exactly how to set it up. Lots of experiments don't give a usable result. But now and again one does, or something unexpected happens. Then we pursue it ruthlessly.

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We get away with such capricious behaviour partly because when it comes to publication, the work is peer reviewed. Other experts look it over, commenting critically and sometimes destructively. For a young scientist, getting one's first papers into print is often a traumatic experience. At that point the work is made open, and the entire research community is implicitly invited to check it, to build on it or to refute it.

At least that's how it should be, and if we really want to have confidence in the results of science then this system should be supported by everybody. Instead, what we increasingly find is that sometimes results not to the taste of the funders simply disappear. Worse, marketing and lobbying present the expurgated picture as if it were the real thing.

Take drug safety, for example. What does this mean? It can never be absolute, though not many people want to accept this. The chemistry is precise, but the test results are ad hoc because we don't know enough about the biology of our own bodies. We shall learn more and more, of course, and the use of pharmaceuticals will be a part of that learning, but there will always be an element of uncertainty; it should be up to patients and their practitioners to discuss openly the risks of any treatment. The difficulty is that the adversarial nature of the free market and the language of political rhetoric are not conducive to truth-telling. So we see major pharmaceutical companies burying evidence of adverse reactions to antidepressants and, conversely, Jesse Jackson exaggerating minor book-keeping irregularities to campaign against cheap drugs being sold to African countries. In the first case, the depressed patient may well be willing to accept a small risk and, in the second, the Aids sufferer is surely better off with affordable drugs than with death. But neither judgement can be made if the facts are obscured.

Many working scientists face conflicts of interest over such matters because patterns of funding push them into contractual arrangements that remove some of their control over publication. Companies and the Treasury are giving more money for science under conditions conducive to profitability, and the proportion of funding without strings is diminishing.

There is a reluctance to admit that different groups in society have distinct primary objectives. A scientist's primary objective is to discover. There need be no conflict between this and making profit; indeed each depends on the other. But judgement of the success or otherwise of scientists rests ultimately on their discoveries. A publicly quoted company, on the other hand, exists to maximise the return on the capital invested in it. This is its primary and legally binding function. It may contribute in many other ways, such as doing fundamental research and being socially beneficent, but in the final analysis no other activity can trump that overriding primary objective. The point to bear in mind is that for a healthy society all functions need to be in balance, and that balance should be exercised by democratic government. However, over the past quarter century, with political will drifting to the right, and triumphalism in the West following the end of the Cold War, we have seen government becoming increasingly subservient to the lobbying power of profit. The free market is supreme, and the scales are loaded.

Now, the free market is a good servant but a bad master. We need ways of conducting research and development that are not purely market driven. How else are we to heal the world's sick and restore justice to globalisation, let alone continue along the road of scientific discovery?

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So we seek ways of truing the balance. These days we hear much of "corporate responsibility" as a means. This phrase is an oxymoron.

Corporations can, and often do, exercise responsibility. But in the final analysis, their decision to do so rests with the finance sheet - this is simply a legal necessity of their functioning. And there is nothing wrong with that, so long as we don't overrate their ethics. Internationally, non-governmental organisations have become increasingly important.

Collectively, they provide an alternative channel of democracy, generating pressure on issues where government has been subverted by corporate muscle.

Suffusing all, and vital to holding society together, is the fourth estate of the media.

Ah, the media. The best are very good indeed: to have a conversation with someone who is well briefed, and interested from the point of view of a non-expert, is an inspiring experience. But obviously a free press is essential, and the only way we can have it is through competition. And that means advertisements, hyperbole and headlines. Headline writers seem curiously unaccountable to anyone, including the reporters they work with, and cause tremendous damage to accurate reporting. But control is impossible without censorship: so we're better off with the system as it is, and we must simply do our best to make it as accurate a form of communication as we can.

How do we, with our various primary objectives, proceed? Naturally, by each taking our share of exposure. Everyone is enjoined to sell themselves and their work. We welcome opportunities to talk to the press. Some of us sit on the sofas of TV breakfast shows. For individual scientists, this is good. It is essential that we communicate. But then we find that we are competing in a new way. We try to improve our act and some of us take media training. This can be helpful, but also builds a facade behind which truth is screened. Corporate scientists don't get free access at all but are filtered through a publicity operation. So parts of the process become a branch of the advertising industry and risk a spiral of distrust in place of the transparency that we sought.

Media training can also become a great waste of time. Ian Gibson, chairman of the House of Commons Science and Technology Select Committee in the last Parliament, criticised research councils for spending money on public relations assistance to deal with government committees (not least his own). I have every sympathy with the research councils. If the Government sets up adversarial accountancy, people have a duty to defend themselves.

But the result is a chain reaction of resource wasting and the generation of further distrust.

But I don't intend to dig a pit of gloom. The current low level of trust has a positive side in that it is not so much a loss as something replacing nothing. Society is changing: people have time, knowledge and tools to question the experts where formerly there was simply a blank wall. The revelations about nerve gas experiments at Porton Down and of unconsented organ retention at Alder Hey Hospital are painful and have given rise to onerous legislation, but they are taking us forward to more trusting relationships. Despite frustrations for some, we must keep talking and move on together. In a technologically complex society, we need independent experts and we need goodwill. We can't trust anyone who is under controls - financial, political, ideological or those driven by ambition - but that's true of all of us, not just scientists. And trust is a two-way process.

Certainly scientists need to communicate, but they should not be called on to adjudicate unilaterally on ethical matters. The job of the independent expert is to explore, discover and communicate. But when it comes to ethical decisions, the expert has just one vote like everybody else.

Government must be by democracy, not by narrow expertise. So in this two-way contract, the non-scientist is called on to think rationally about the decisions to be made.

There are burgeoning tools to help the process along. The Royal Society and the Nuffield Council, schools and the caf¨¦s scientifique , websites, the Economic and Social Research Council units and the government commissions are all are falling over one another to give meaning to "science and society". None of this is to suggest that scientists should be off the ethical hook any more than anyone else. We should all accept responsibility for what we do. The fact that your mortgage is at stake does not entitle you to take a job making illicit weaponry, but it may persuade you to go along with socially undesirable practices. It might be good if scientists had a professional code of conduct, both to set standards and to support individuals who come into conflict with their employers over their observance. Such ideas have, however, found little support, perhaps because the anarchic nature of science militates against control. Some codes of conduct do exist - the Institute of Biology has one, for example. But for the moment it will be essential for heroic individuals (of whom we have a few) to blow whistles and for external regulation to provide better frameworks.

But, please, don't make scientists the scapegoats. It's not a question of distrusting scientists, it's that people don't trust one another. After all, under Margaret Thatcher and still under new Labour we all are taught to look chiefly to our own gain. Until we finally turn our backs on the Thatcher's dictum that "there is no such thing as society", distrust will be a part of our style. In my experience, scientists are among the most trustworthy members of society - but then I would say that, wouldn't I?

Anyway, behind any individual scientist, who is no more than human and has his or her own personality and obligations, lies the enduring value of science as a discipline. I don't mean just the knowhow and the material accomplishments. The role of science as a cultural driver is clear, and one does not have to be a professional to feel that this extraordinary voyage of discovery on which we are embarked is part of the purpose of human life.

Beyond all that, though, the practice of science in itself demands acceptance of principles that can only be described as moral. It demands international co-operation, acceptance of diverse talents and contributions; it rejects arbitrary dogma in favour of evidence of the senses and rational thought; it values life before death; and it looks to the future. Those who care for the human race, indeed for its very survival, may ponder the morality of science, and consider whether it offers the best basis we have for organising our world.

Sir John Sulston, founding director of the Wellcome Trust Sanger Institute, shared the Nobel Prize for Medicine in 2002.

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