Of all the emotions that one could deploy in order to change people's minds, doubt has to be the most useful. Panic is the easiest. We can all imagine the impact of shouting fire in a public place. Fear is the least containable - it can quickly become a contagion and unleash unintended consequences that cannot be managed.
But doubt, there's the thing - quiet, seeping, gnawing away at our certainty.
There are many places in public life where doubt can be helpful to those who may not want the government to take one action rather than another.
Do we need to keep the 50% tax rate? Should we break up the banks? Should there be a Plan B on the cuts?
Those who want to change minds one way or another can use doubt to create room for manoeuvre.
So how might you do it?
First, recognise that there is little certainty out there in the first place. Most of us are pretty sure about what's happening now, but we're a lot less certain about what might come next. So any message that an interested party might push out into the public domain would, in all likelihood, land on fertile plains. Only zealots are absolutely convinced - most of the rest of us like to wait and see.
Next, develop a series of phrases that sound as if they make sense. Here are a few that are sure to work. "Now's not the right time to be doing this", "the recovery is fragile" or "our best talent will leave the country if we do that". The great thing about these kind of phrases is that they sound about right - they're likely to get nods or at least tentative interest at your average dinner party or evening in the pub.
But phrases alone won't do it. You've got to get people to say them. You have to add some weight. So roll in some who might benefit from exposure. Talk to politicians keen to get fresh airtime. Furnish them with killer facts that can be dropped into interviews on the subject - the potential lost tax revenue if our multi-zillionaires move to another country, the likely rise in interest rates if we fail to convince investors that we're serious about cutting spending, the number of nurses that would have to be cut from our hospitals as a results.
You could put together a panel of experts and ask them to write a letter. A weighty group of economists saying something challenging on a slow news day will give you all you need: exposure. Last week, the BBC reported that twenty high-profile economists were urging the government to drop the top 50p tax rate, because, they said, it is causing "lasting damage" to the UK economy.
It was clearly a very slow news day because this story led all day. Most helpful.
Now, when people are talking about the big issues - the banks, tax rates, the cuts - they've got in mind an alternative view. Doubt is creeping in. Where they might have been unalterably certain that the bankers should get their comeuppance, that the bazillionaires ought to be paying their share, that the cuts were too savage and too fast, now, many people are not so sure.
When doubt is in our minds, it feeds on itself. We're still hard-wired for the savannah. Although we know that the world is not governed or interpreted by runes, many people still read horoscopes, think about what odd events might tell us, worry about tempting fate. Deep inside, we're still worshipping the gods of Good Weather and Plenty.
So what next for the doubt-merchants?
Ideally, a survey would be helpful. Politicians will not lead unless they're following the crowd. So you've got to know what people think. A survey that showed, for example, that people believe breaking up the banks could endanger our recovery could create the wriggle room needed to change or soften policy. When you've got the results, feed them everywhere. Again, exposure is vital.
Finally, to close off any intellectual challenge to the doubters' position, arm your heavyweights with alternative but simple arguments. For example, breaking up the banks would not have stopped the banking crisis since it started in the retail not the investment business. Or if we slow down the programme of cuts then the UK will go the way of Greece and Ireland - rising interest rates.
Doubt is a very powerful weapon. It's two fighters standing toe-to-toe. Both are pumped with adrenaline. Then for the briefest of moments, one doubts himself - a lapse in belief, a fleeting thought. It's enough. Before he can draw breath, the killer punch lands and the fighter's jaw shudders. He's down and out.
It's all over.