We expect that our newspapers, radio and television offer us an objective view of the world; that reporting is without bias and is value free. We expect opinion to be clearly marked as such - even published on a separate page so as not to "contaminate" the objective news reports.

It's true that some areas are excused from this central tenet of modern journalism: tabloid newspapers mix fact and opinion - front-page headlines will scream "Cowards!" after a terrorist bomb has killed people. During elections in Britain, the front pages of the Sun and Mirror have often looked more like partisan posters than newspapers.

However, most publications take the idea of objectivity very seriously.

Radio and television have a special responsibility to be fair, non-partisan, balanced and objective in their news reporting. In many countries this is written into legislation - here, both RTE and the independent commercial radio sector must be unbiased. The same rules will apply to TV3 when it comes on air later this year.

It was not always like this. Until the early years of this century newspapers were aligned to political groupings, or had clear opinions and were associated with factions. In the past newspapers, mainly family-owned, often with an editor who was also the owner, were as partisan as they liked. They had opinions and those opinions were reflected in everything written.

Many newspapers still are opinionated - but they generally try to make a distinction when it comes to news coverage. Their editors will say that while the newspaper supports something in its editorials, the news coverage will reflect the objective truth.

origins of objectivity

There were three factors that changed the way news was written and introduced the notion of objectivity as a central plank of journalism: the news agencies, the growth of corporate ownership of newspapers and the introduction of regulated and public-service broadcasting.

With the invention of the telegraph the sending of news long distances quickly became a practical possibility - no more carrier pigeons, as used by Julius Reuter when reporting the Franco-Prussian War. The telegraph allowed, for example, the Associated Press in the US to send news right across the continent and to be used by hundreds of subscribing newspapers, all with differing editorial policies. So stories were sent with as few value-laden words as possible. Values and bias were for newspapers - not for agencies.

The role of corporate ownership is a bit more complex. Professor Jay Rosen of New York University says one simple way to understand objectivity is to see it as a contract between journalists and their employers: journalists are allowed to report the news independently and be left alone - and the owners will not have to be troubled about the journalists' politics. The need for this unofficial contract arose in the 1920s and '30s when corporations began to either buy or establish newspapers. One side provided the news and the other the plant and machinery for the journalists to do their job. "The name of that negotiated peace was objectivity," Rosen says.

With the development of radio, and later television, some government regulation was necessary to ensure that there was no frequency chaos on the dial. Unlike newspapers, it was necessary to license and regulate broadcasting, because the wave bands offered only limited accessibility. This gave governments a huge influence - something newspapers had fought against for the previous 200 years. State-imposed notions of objectivity and impartiality meant, theoretically at least, that coverage would reflect all sides and arrive at truth and objectivity via balance.

unease with the concept

Today there is some unease with the concept of objectivity. Journalists who speak or write the word "objective", often follow it with "whatever that means".

Objectivity and impartiality, many journalists now say, are impossible to achieve. The journalist's selection of facts alone means a subjective and partial element can enter into a news story. More often than not, objectivity is considered no more than something to aim for, unlikely ever to be achieved - like utopia.

What many journalists say they offer, instead, is fairness.

Objective reporting has little to do with truth or validity or the elimination of bias from a story. What it is about is eliminating from news stories the intrusion of the journalist's bias and values. To do this a number of devices are employed: value-laden vocabulary is avoided; the third person is used; and, most importantly of all, stories are attributed to a source - as is the interpretation of those stories.

Another way to understand objectivity is as a set of professional routines and procedures - things journalists habitually do when they report the news. The reliance on official sources, because they seem to be credible or objective, is one such routine.

Another one is to quote both sides of a political dispute; that is the routine we call "balance".

the limits of balance

This would appear to be totally fair. But what if you had a story reporting the tobacco lobby saying that smoking is basically fine, and the cancer society saying it is dangerous. If you balance these positions, that means the story is actually offering a non-truth. Some media experts see objectivity as a way that journalists escape responsibility for the truthfulness of their accounts.

Those who study the media are now looking at ways to offer news in a way that is as near an approximation to the truth as is possible. They are also suggesting that journalists must be aware of the effect of what they write or broadcast. They are saying that journalists cannot hide behind a series of professional routines and then deny any responsibility for what effect their stories might have.

Violence against some people for instance - is it good enough for journalists to say their reporting about refugees and asylum-seekers is accurate and objective, if it also leads to attacks on such migrants?

There are deeper, more intellectual objections to the idea of objectivity. Objectivity can be seen, after all, as a theory to get to the truth. That states if you separate facts from opinion, news from views, this will permit you to reveal the truth. The usefulness of this conception depends not only on an individual journalist's ability to separate those things, which is tough enough, but the logical validity of doing so. Is it really always possible to distinguish something called information from something called opinion, to distinguish fact from values?

Everything in the development of philosophy, psychology and science seems to go against such a distinction; journalists seem to be the last refuge for the idea of objectivity. No one else takes the notion seriously any more. When journalists say that if they cannot be objective, they want to be fair, they are exchanging the pursuit of truth for a value. One result of this "on the one hand, on the other hand" journalism is that political coverage can see the world in terms of extremes, with one lot saying one thing and other people saying the opposite. The easiest way of achieving balance is to take two extremes and run them together. But is that any way to achieve truth?