Johann Hari: When the Government acts, why do we always assume there is something to fear?

Once the DNA database became available, police found hundreds of rapists and jailed them

The Seventies pop screecher Leo Sayer announced last week that living in the Celebrity Big Brother house is "like being in Abu Ghraib". When another contestant pointed out that the tortured Iraqis weren't being paid hundreds of thousands of pounds and didn't have the option of popping into the diary room for a chat, he conceded. "Okay, I see what you mean," he said. "It's more like Guanatnomo Bay."

I don't know why everyone laughed. The people who will ritually jerk their knees today by declaring that Tony Blair's proposals for a simple centralised Whitehall database are "a step towards tyranny" sound startlingly similar.

The Prime Minister is proposing to make it easier for government departments to share information. The Department for Work and Pensions will be able to find out from the Department of Health which pensioners are so sick they count as disabled, so they can give them the hundreds of extra pounds they are entitled to every month. The Housing Department will be able to find families who are slipping into financial chaos and help them out before they turn up at their local town hall one day, clutching their kids and some hastily stuffed boxes, after being evicted. The Land Registry will be able to catch more middle-class people who cheat on their council tax returns by not declaring home extensions. If it succeeds - as it has in most democratic countries - the state machinery will become smoother, faster and more efficient.

Yet these proposals are already being presented by the Conservatives - and many on the left - as yet another step into 1984, part of a proto-tyrannical package ranging from CCTV cameras to Asbos to the DNA database that they cite as evidence Britain is sleepwalking into a surveillance society.

Most of the people who are tetchy and tense at news of more government powers are good people with good worries. Blair's government has abused civil liberties. They reintroduced internment, and only ditched it in favour of the almost-as-awful house arrest because the House of Lords forced them to. They allowed British airspace to be used to "render" human beings for torture in secret US prisons in Eastern Europe. They slashed back jury trials. They imprisoned refugees and their children in camps, for the "crime" of seeking asylum. They tried to criminalise fierce criticism of religion. I wouldn't trust that old Stalinist John Reid with a kitten, never mind fundamental freedoms - so everything the Government proposes needs to be scrutinised carefully.

But there is a danger that, in response to these real abuses, we have ended up with a right-wing reflex reaction. If we assume all state action undermines human freedom, we will end up opposing smart measures that help people along with the ones that cause real harm.

The philosopher Isaiah Berlin famously drew a distinction between "negative liberty" and "positive liberty". Negative liberty is freedom from interference by the state. Positive liberty is freedom to achieve your goals - and sometimes, that requires help from the state. Most of us have now sunk into an unspoken belief in negative liberty alone. When we hear the government is acting, we automatically assume there is something to be feared - as though government can only take liberty, and never help us to achieve it.

Look at the recent creation of a DNA database. Many people (myself included) reacted with an instinctive retch. What right does the state have to store my DNA? But then positive liberty enters the picture. The biggest civil liberties violation happening in Britain - by far - is the epidemic of unpunished rape. Some 50,000 women are raped in this country every year, and only 600 of the rapists ever end up in jail. That's not a problem of too much state action. That's the state failing to act. Women deserve the same positive liberty to walk the streets at 3am as anybody else - and the hard evidence shows that the DNA database helps to ensure they can.

Once the DNA database became available to the police, forces across the country started to trawl through their 'cold' rape cases, the ones lying dormant in their files with no new leads. By checking the old blood and semen in the archives against the database, they found literally hundreds of rapists and jailed them before they could rape and rape again. (We know from all the research that rapists rarely stop with one woman). To pluck one small police force at random: Avon and Somerset Constabulary have used the DNA database to catch Nigel Palmer-Batt, a man who forced his way into a 21 year-old woman's flat in 1979 and raped her. They used it to catch Jason Reed, who raped a sex worker in 1992. They used it to catch Ron Evans, who raped a woman in Bristol in 1977 and sexually assaulted another woman two years later. The list goes on. All this has been achieved with only 5 per cent of us being stored on the database. If all of us were, rapists would have real reasons to be afraid.

The Big Sister state has saved thousands of women from rape by taking this positive action. The DNA database has become a feminist tool. But if we only see the world through our anxiety about negative liberty, we won't see all these women who have been rescued. This is hardly a lone example. Thanks to CCTV, many people - particularly women - feel safer at night. Thanks to Asbos, people living on some of the poorest estates in Britain have been saved from constant intimidation. These are net gains for freedom.

But a rigid, no-exceptions belief in negative liberty is still tempting, because it allows you to have a quick response to every proposal: state bad. You don't have to look at the detailsor the victims. You can feel morally superior. Yet in reality, freedoms often compete with each other. It is a very small violation of liberty to have a swab put in your mouth for a DNA sample; it is a very large violation of liberty to be raped. People who really want to maximise human freedom have to make hard decisions in weighing one against the other.

We all have to do this, slowly, agonisingly, with every government proposal. Often this will lead rational people to oppose the government proposals of the day. For example, I can't see any gains in human freedom flowing from ID cards, and I can see plenty of drawbacks - like giving the police an excuse to harass young black men who are simply walking the streets.

But the automatic we-must-stop-this-Government-plan paranoiablocks out thought, and has percolated into ridiculous areas. Recently, Patricia Hewitt suggested computerising the NHS's medical records. This would save hundreds of lives: I know of at least one person who died because she was taken ill out of GP hours and her written records couldn't be easily accessed. Yet when I discussed this on the radio recently, many in the audience reacted as if it was part of a semi-Ba'athist plan to erect a police state. No doubt this sensible new Whitehall database will sound to them like the thud of a jackboot.

When did we all start singing Leo Sayer's songs?

j.hari@independent.co.uk