Fear gives politicians a reason to be

There is a real threat to this country from extreme Islamist terrorism. There is a real possibility of a terrorist attack that will kill and injure many civilians, and so far the security services have worked extremely effectively to prevent this. But the idea that behind this threat is a uniquely powerful organisation with hidden networks of sleeper cells across the world is largely a fantasy. The reality of Islamist terrorism is that it is disparate and complex, driven by an idea and not by an organisation.

But it is this fantasy that is being used to justify many of the extraordinary special measures that the government has outlined in the Queen's speech. It is a price we are told that society has to pay when faced by such an overwhelmingly powerful enemy that is unlike any other terror threat from the past.

In many ways the political use of fear is nothing new. Of course politicians in the past have exaggerated threats for their own advantage, but this time it is different. In the past it was always in response to another political threat to their power - whether it was internal, from the organised working class, or from abroad. This time they have turned to fear not because of a real enemy outside, but because they feel their own sense of legitimacy and authority dwindling.

In the period roughly from the end of the first world war through to the economic crisis of the 70s, politicians on both the right and the left believed that they could use the powers of the state to reshape and change society. This was a belief common to the National Socialists, Clement Attlee and the Keynsians, and US president Lyndon Johnson. This belief flourished in the post-war years, and out of it came a wide cultural influence of politics because it offered a vision of a new type of world which everyone could work towards.

The architects of this vision were the politicians, and this gave them great authority because they not only managed society but they gave a meaning and purpose to people's lives. That idea of progressive politics collapsed in the crisis of the 70s - and out of it came the modern pessimism that society is too complex an organism to be changed in a rational fashion. The alternative was allowing the hidden hand of the market to guide and shape society - and so politicians like Mrs Thatcher gave away to the market the power that previously had been held by the state.

This has increasingly left the politicians with a loss of authority. Although some, like Gordon Brown and Bill Clinton, do - or did - promise to make health and education work better, they are not promising to change the world, only to manage it in a more efficient way. (Clinton, guided by Alan Greenspan, head of the Federal Reserve Board, gave away the last vestiges of political control over the economy, much as Mrs Thatcher did.)

It would be impossible for Lyndon Johnson to make his famous "great society" speech today: that idea that politicians can change the world would be laughed at. Of course there is massive social and economic progress, but it is no longer perceived as having been produced by politicians. Politicians and politics don't give meaning and purpose to our lives any longer, and this has created a crisis of legitimacy for them. If all they offer is a better managerial style, then why should we vote for them? This is one of the reasons New Labour remains so dominant despite all crises - because no one believes the alternative will be any different. The Conservatives don't have a vision to offer, merely the promise of sacking more civil servants.

This is why I believe that politicians have found in fear a way of restoring their power and authority and recreating a sense of legitimacy. I do not in any way think it is a conspiracy - they have just stumbled on it. Put simply, they have found a grand, dark force to protect people against, and they can use the power of the state to do this. It is a mirror image of the positive future they used to promise us. But now it is a frightening future they promise to protect us from.

This is largely a fantasy: of course there is the threat of Islamist terrorism, but not from the organised, sinister network they portray. And it represents the last gasp of a liberal political elite to maintain their sense of specialness in society. The reality is that there are many new elites in business, science and the media who are creating the new progressive visions, and the age of politics as a system that gave meaning and vision to society may be dying.

Or we may be living through an incredible era of prosperity and calm in which politics as a force for transforming the world has gone into abeyance - and when a real crisis comes along, politics will return in a new form we cannot possibly imagine.

· Adam Curtis wrote and produced the recent BBC2 series The Power of Nightmares: the Rise of the Politics of Fear