On the face of it, it seemed a little odd. Back in 1994 Newt Gingrich’s pollsters were testing his proposed Contract with America when they stumbled across a puzzling inconsistency. When voters were asked if they thought that benefits should not be given to lone parents who refused to work, they strongly agreed. But when asked if those parents should be denied benefits, they were much less favourable. The policy appeared the same, the support for it very different.

What the pollsters were witnessing was actually something quite common — the finding provided an example of what academics call the Status Quo Bias.

The way that the question was posed presented voters with two different views of the status quo. If the status quo was for benefits to be given to people, voters didn’t want it to be denied. If the status quo was for benefits not to be given to people, voters did not want it to be given.

The status quo bias pops up again and again in politics. When voters in New Jersey and Pennsylvania were presented with identical choices in a ballot on car insurance law, both voted heavily for opposite policies, both sticking to the status quo in their state.

Behind the status quo bias is this — people tend to regard harmful actions as being worse than equally harmful inaction. They overestimate the risks of acting and underestimate those of failing to act. For instance, some parents fail to vaccinate their children because they prefer to leave them exposed to the fairly large risk of disease than to the tiny risks involved in a vaccination they have actively procured.

And here’s another example — our policy towards Iran. Hardly a day goes by without an exposé of US plans for a military strike on Iran. The risky nature of such a venture is emphasised. The danger of failing to act receives far less attention. We believe that Iran, a fundamentalist state with a history of sponsoring terrorism, is six months away from being able to enrich uranium on an industrial scale. We think it is determined to possess nuclear weapons and will get its wish within a few years. And yet we are far more scared about acting than we are about not acting.

The first reason for our preference might be called the Dodgy Dossier Dodge. Because intelligence reports suggested that Iraq had weapons of mass destruction and we were unable to find any, the idea of acting against Iran seems obscene. What if the Iranians are telling the truth when they say that their nuclear programme is not military?

This is a reasonable question. It’s hard to know about weapons of mass destruction. For years we grossly underestimated Saddam’s nuclear programme before new intelligence revealed the truth. But why would we prefer the optimistic view of Iranian intentions, when the consequences of being wrong are so great?

One reason is the Equivalence Argument. You hear it all the time in the Iran debate. How can we lecture the Iranians, when we are upgrading our own weapons system? Why shouldn’t they have nuclear weapons if we do? Yesterday the director of the International Atomic Energy Agency, Mohamed ElBaradei, made this point. And it has force, if you can’t see any difference between the Government of Iran and those of Britain and the United States. But I don’t regard this as a very difficult distinction to make.

If Iran succeeds in obtaining nuclear weapons it will embolden it to pursue an aggressive foreign policy, supporting terrorist activities and antidemocratic forces around the globe. It is incomparably more dangerous to peace and democracy than the modernisation of Trident.

A more understandable reason for the status quo bias on Iran is what might be called the Clock Illusion. In his superb book The Persian Puzzle, former Clinton adviser Kenneth Pollack talks about Iran policy involving two clocks — the regime-change clock and the nuclear clock. The aim of policy, some say, should be to speed up the regime-change clock and topple the mullahs, rather than slowing down the nuclear clock.

But, as Pollack points out, this is hardly realistic. Regime change in Iran, although unpredictable, still seems further away than the acquisition of weapons. In any case, the history of attempts to change the regime in Iran from the outside has not exactly been encouraging.

Which leaves the last — but still the most potent — of the reasons for the Iranian status quo bias. There is an almost universal belief that nothing can be done. And I don’t believe that this is true.

It is often argued that the war in Iraq has made action in Iran impossible. But the truth is different — the truth is that an invasion of Iran would always have been a stupid idea. Iran is four times the size of Iraq with a population three times the size. Its mountain ranges would aid the insurgents and the Iranian people have a history of fiercely resisting foreign interference.

But there is a much stronger case for military strikes against nuclear installations. Naturally, the Iranians would be enraged and there would be massive international condemnation. But the upside is that the Iranian nuclear clock could be slowed or even stopped. The only really good argument against military strikes is that we can’t be sure where Iran’s nuclear facilities are. They’ve proven adept at concealing such things.

Because of this uncertainty, and because aggressive action should always be avoided if it can be, such military strikes are a last resort. But I cannot understand those who, like The New York Times, insist on clarity about our intentions or those like Jack Straw who, as Foreign Secretary, repeatedly said that military action against Iran was inconceivable. Why would we want the Iranians to know that? Why wouldn’t we want them to fear that strikes may result from their policy? Isn’t uncertainty and lack of clarity a potent weapon?

History suggests that it is. On a number of occasions since the 1979 revolution Iran has pulled back from an aggressive policy because it feared either military retaliation or serious sanctions. Yet now we are afraid to threaten it with either.

Earlier this week Russia suggested that the launch of the Iranian nuclear reactor at Bushehr could be delayed because Tehran had fallen behind with its construction payments. US financial sanctions are clearly biting. Yet European nations still refuse to join in. For goodness sake. What are we waiting for?

Times Recommends

• Fundamentalist brew: faith and power
• Big guns wheeled out for the marginals
• Wanted: new merchants of light