Careless talk: In the third of our profiles of artists shortlisted for this year's Turner Prize, Charles Hall finds Willie Doherty dramatising the gulf between images and the meanings we casually ascribe them

Willie Doherty lives and works in Derry. Many of his close neighbours think they live somewhere called Londonderry. It's a little linguistic disagreement which could, until quite recently, have wound up with someone dead. According to the cliche, an Englishman can't open his mouth without having somebody hate him. For an Irishman, until very recently, the problem was more acute. Careless talk cost lives.

As a result, the people of the city have developed a rare consciousness of the kinds of nuance which are normally reckoned to be the sole concern of dry-as-dust academics and ivory tower contemporary artists: when nationalist forces blew up a monument to an Orange general, the rubble was cleared away because it was considered to have become a monument to nationalist terrorism. This is the obsession - with the naming of things as a means of annexing them for a particular political territory - which holds together the disparate strands of Doherty's career.

'When I was making the initial black-and-white photographs about Derry, my starting point was looking at how the political and physical landscapes were fused. To have a knowledge of one gave you an insight into the other.'

These photographic works, which first made Doherty's name, tend to consist of, for example, distinctly unphotogenic images of shabby country lanes or concrete walkways, or (given that these are shots from 'troubled' Ireland), equally ordinary views of high fences, dead-ends and burnt-out cars. Most of these views come complete with stark, dead-pan texts: 'Enduring', 'Double Vision', or 'God has not failed us'. To the uninitiated eye, these photographs can look banal. There are plenty of conservative - and not so conservative - critics willing to dismiss them as 'worthy but dull'. Some simply claim that, as photographs, these are not visually striking; others see them as parochial reworkings of the kinds of conceptual investigations already overfamiliar from the works of Barbara Kruger and Gerhard Richter.

But then, the fascination of Ulster lies in the fact that images of it do not have to be visually striking to be culturally charged. Non-specialist viewers on the mainland might see the blankness of the images as alienating (this is not art because it is not beautiful; its dependence upon ideas removes it from the matter-of-fact reality of our everyday lives). But when Irish viewers are hostile it tends to be because 'I lived it for years, and it didn't feel like art to me'. Which is another way of saying that the subject of these works is too familiar to be dignified with the name of culture.

At first sight, one would imagine that Doherty could be neatly pigeon- holed as a Nationalist artist - perhaps even as one of the so-called 'helicopter artists' who have disguised their own vacuity by churning out routinely anguished images of a 'war-torn' province. But Doherty rises above this in that the charge of his work lies in our dawning sense of powerlessness, rather than in any conversion to his position. In Same Difference, for example, mugshots of Donna Maguire (found not guilty of IRA activities in four European countries since 1989) are projected on to opposing walls, complete with a series of mutually-exclusive labels: 'Murderer Delirious Murderer Impulsive Murderer Aggressive' on one wall, 'Volunteer Daring Volunteer Fearless Volunteer Embittered' on the other. The cumulative effect is to strip away our faith in our ability to ascribe meaning to anything at all, until we're left with nothing more than a photograph of someone we do not know, cannot judge or understand - that, and a distaste for those, on both sides of the divide, who foist these apparently authoritative verdicts upon us.

The very drabness and terseness of the texts Doherty inflicts on his photographs parody the certainties of speakers who consider all arguments closed. The one exception to this comes in an installation, They're All the Same, in which a projection of the face of an IRA man was accompanied by an audio tape in which an attractive male voice alternated between a series of phrases defining his identity as a terrorist ('I am proud and dedicated. . .

I am patient. I have a vision') and bog standard travelogue: 'The clean sweet air is interrupted only by the lingering aroma of turf smoke.' The implication is that political extremism is inextricably intertwined with a romantic (and anachronistic) identification with 'the native soil'. This perception may also go some way towards explaining Doherty's indifference (or hostility) to conventional notions of photographic beauty. Transcendence is dangerous - at least until we can agree about the realities that we are trying to transcend.

The thrust of the work, then, is to purge us of the language that we have brought to the 'problem' of Ireland. Take, for example, Alleyway, a photograph that appears to show the entrance to a dark, dangerous tunnel, enlivened only by a squarish block of light emanating, one assumes, from a security video screen. It is, in fact, a streetlight. 'That presumption is exactly what I'm looking at. Given the knowledge you bring to Northern Ireland, it becomes very difficult not to see what could be an innocent alleyway in a loaded way. That's why I don't think that peace will render this work redundant at all: it has always been about trying to evolve a new kind of language: saying hey look, stop look at this, what is it about, where does it take us, looking at those roles and talking about that fear.

When I made that particular photograph, the Northern Ireland Office were broadcasting a series of films very graphically depicting sectarian murder, long before the watershed, and they looked like Reservoir Dogs. The unstated implication was that if you don't co-operate with the authorities, you're dead.'

'What this imagery did was to perpetuate the cycle of hopelessness, which was the situation 18 months ago, when everyone was in the position where you were the next victim. The Government was saying these people are crazies, there's no way of talking to them, there's nothing we can do to stop them, - the only language was intimidation.'

It's hard to know exactly how to discuss Doherty's work, let alone his role, in the new Irish situation (the imagery of his next film, At the End of the Day, with its country roads and roadblocks, is already verging on the anachronistic). It is tempting to ask whether he sees himself as more a creature of the worlds of politics or art but, once one has accepted the premise of his work so far, the distinction itself seems utterly crass.

Doherty has always worked in the context of the visual arts. He admits to having learnt from Richter's formal innovations, and to hoping that a specialist audience will admire his own contributions in the field. Indeed, his art-world reputation extends far beyond Ireland or indeed Britain (he was in New York last week, spent three days in Derry this week, and is in London today to edit the film that he plans to show at the British School in Rome this November). He was, after all, involved with performance and installation art long before he made the photo-text works with which he is now principally associated ('They inevitably ended up being photographed - all you ended up with was a bunch of photographs, so it was logical to work directly with that').

But in a society where the very idea of interpretation is so highly charged, and where language is now 'shifting and cracking' day by day, as politicians explore new and less divisive ways of thinking and looking, it makes no sense at all to attempt to distinguish between 'culture' and real life.

Which means that Doherty will continue to thrive - and to confuse those who assume that the one should be infinitely superior to the other.

Works by artists shortlisted for the Turner Prize will be at the Tate Gallery from 2 Nov-4 Dec (Photograph omitted)