Can anyone tell the whole truth and nothing but?

Lord Hutton is charged with untangling the Kelly affair. Is such a search for absolute veracity an impossible task, or is the truth out there? asks Sean Coughlan.

When the Hutton inquiry into the death of scientist David Kelly began, there were suggestions that the famous truism could be reversed and, for the first time, war would become the casualty of truth.

Even though information and evidence, opinion and comment have been produced in abundance, the prospect of an agreed truth about events seems remote. Even where facts have matched, interpretations have differed.

Perhaps there have been too many different truths on offer. The scientific pursuit of truth, in its purest sense, depends on drawing narrow conclusions based on large amounts of evidence collected in a spirit of independent inquiry - for politicians and journalists, the opposite can be the case, with a narrow slice of information being used to draw wide conclusions based, in many cases, on protecting vested interests.

None of these approaches is necessarily dishonest - if we understand how they operate - because they all have to serve different audiences in different ways. But can so many divergent perspectives all be truthful at the same time, as a postmodernist might argue? Is it all about negotiating a multiplicity of subjective narratives, or is one form of truth more truthful than others?

Despite endless debate about the pros and cons of postmodernism, what is certain is that it has contributed to an uneasiness about truth and trust and to an awareness that there may be different cultures of truth. But what happens when two different cultures of truth clash, for example, when academics are called to give evidence in court or are put under the spotlight of media "truth"?

Scientists have had a particularly unhappy experience recently with countless examples of their version of the truth being distorted when they are held up in the public arena. Although scientists might cautiously frame their findings with "we're not sure" and "more research is needed", media accounts are less troubled with such detail and often sweep away the academic caveats.

Keith Campbell, professor of animal development at the University of Nottingham, experienced some of this clash between scientific research and media hype when he was part of the team that produced Dolly, the cloned sheep.

"We've seen all sorts written about it," he says, remembering in particular how years of groundbreaking research ended up as the newspaper headline: here sheep are sheep and men are nervous." He says that there are pressures to take the sober facts of a scientific discovery and use them as a springboard for more dramatic claims.

"It's not very good for a paper to have a boring story saying scientists have cloned a sheep and that this might lead to medical improvements in 15 years. But if you say we've cloned a sheep so we'll be able to clone a human next week, that's going to sell much better."

Behind these different understandings of the truth, he says, is a cultural gap that scientists must recognise. "What we don't realise is that whatever walk of life we're in, we've all developed different vocabularies. When we meet in the middle, the words may mean different things to different people."

This risk of words being misunderstood or taken out of context arises when scientists talk to non-scientists, Campbell says, with technically complex scientific "truths" getting lost in translation, whether it is a journalist or a university press office looking to capitalise on research.

In practice, he says, it might be that a scientist is not the best person to talk about the technology unless he or she understands and can negotiate the language gap.

If scientists and journalists can deliver widely varying interpretations of the truth, is truth a subjective free-for-all, where anyone's view is as valid as the next person's?

This is a subject that has been the centre of philosophical debate for generations, and one that the late Bernard Williams, arguably one of Britain's greatest philosophers, spent his last years on.

Robin Hendry, senior lecturer in philosophy at Durham University and until recently secretary to the British Society for Philosophy in Science, says that from a philosophical perspective, truth is not simply a subjective matter.

For something to be true, he says, it is not enough for someone to say that it is true. There may be many approaches to establishing truth, and many arguments to support claims, but that does not mean that they are equally valid.

Truthfulness needs to be able to be tested, he says. The proponents of creationism and the theory of evolution both lay claim to the truth, but philosophers would look to how they could be proved, using evidence such as the fossil record, and they would rather make a judgement than accept two conflicting "truths".

Hendry adds that the concept of truth has been interwoven with concepts of morality for centuries, and although fact-based and value-based truths can be separated, it can be difficult to unpick them at times.

Even in our secular, ideology-free culture, truth is not just a matter of opinion, Hendry says. "People might be more critical about belief and less likely to accept the authoritarian handing-down of values, but philosophy should be able to distinguish and check what is true."

Psychologists lean much more towards a subjective interpretation. If challenged to find the truth in an inquiry, they would arrive armed with an awareness of human fallibility when it comes to giving evidence.

Gary Fitzgibbon, who has a psychology consultancy in London, says "memory is notoriously unreliable". What we consider to be a true answer can be influenced as much by how a question is asked as what we think we saw.

We are driven by an "unconscious urge to satisfy the questioner", he says, and that can lead to delivering the truth that we think is wanted, which can mean "embroidering" memories. In its more extreme form, this takes the shape of "false memory syndrome", in which people, responding to questions from a therapist or counsellor, recall memories of events that have never happened.

But it is politics that has raised embroidery to an art form and is awash in talk of a crisis of trust. However, even if politicians knew what the truth was and wanted to publicise it, would it really be possible for them to speak it all of the time?

Paul Whiteley, professor of government at the University of Essex, says that absolute honesty would be impractical because it would produce so many rows that nothing would ever be achieved.

At the same time, he says, even though voters do not expect the whole truth all the time, a politician who gets a reputation for dishonesty is in deep trouble. "Once people stop believing them, they can't reinvent themselves, they can't dig themselves out of a hole. They can't function as a politician."

The spinning of news is a dangerous temptation, Whiteley says, because it encourages politicians to think that they can recast the truth in a way that better suits their message. From there, "it's only a short step to thinking that they can do anything they want".

"But there are limits to this, because there is a reality in politics, and if you go too far, people will simply stop believing anything. It will be like the old Soviet Union with the newspapers Pravda and Isvestia, where people used to say that 'There's no news in the Truth [ Pravda] and no truth in the News [ Isvestia ]'."

But intriguingly, he says that research suggests that what shapes our judgement about whether a politician is telling the truth is not necessarily the accuracy of what they say. Instead, we tend to believe people with whom we feel we have something in common, such as those who look and sound like us, or appear to have the same values and ambitions.

The other factor in plausibility, Whiteley says, is the perception of competence. We tend to believe people who seem to know what they are doing.

Margaret Thatcher, he says, had support from people who did not particularly like her but who trusted her capacity to deliver.

In this, he says, the electorate's concept of political truth is not one of finding moral absolutes but is more of a self-interested view of whether a politician will give them what they want.

Modern politicians face an unprecedented level of public scrutiny, and rather than uncovering political truth, the effect can be to push political decision-making deeper underground, Whiteley says.

The searchability of huge amounts of documents, email trails and records of phone conversations, such as those heaped up for the Hutton inquiry, means that less will be put into writing or discussed on the phone, and there will be "more conversations out of earshot in the park".

It would be an ironic turn of events if our hunger for accountability led to our public leaders having to adopt the tactics of dissidents seeking privacy in a police state.

Would those disappointed to find no immutable truths in politics be better off looking to the legal profession?

Lisa Webley, a lecturer in the law department at the University of Westminster, says new students begin with the assumption that there are "right" decisions, rather than decisions that are as correct as possible, with all the best information available.

Absolute truth will be as elusive in the courtroom as it is in the rest of life, she says. Even when witnesses are certain of the truth of their own evidence, experience shows that mistakes and misperceptions are not uncommon, she notes.

Webley cites an experiment that was done at a US law school to show students the fallibility of "true" observations. In the middle of a lecture, someone ran into the room waving what seemed to be a weapon. When students were asked to describe what they had seen, accounts varied greatly. They disagreed over the type of weapons, the descriptions of the intruder and even the number of people involved.

"People take an oath to tell the whole truth, but they have only a partial view. It's not lying, but they can have different perceptions. The practise of law makes you more suspicious about what people say they have seen, and students have to learn that things are not as straightforward as they might seem."

So, as they used to say in The X Files, "the truth is out there". We just might not agree on what it looks like when we see it.