The great Tom Paine, when he boldly set out his case for American independence in 1776, promised his readers "nothing more than simple facts, plain arguments and common sense". What could be sounder? Not fancy or intellectual talk, just common sense, stuff that ordinary people can see is obvious. Paine, writing in a restive Philadelphia, knew what he was doing.
Common sense was evoked again last week in support of passenger profiling, and its allure was as powerful as ever. Everybody, including grandmothers and six-year-olds, is caught up in the new security restrictions on air travel, and passengers and airlines alike are hopping mad about the delays caused because absolutely everyone has to be scanned, searched and warned several times before they can fly away.
Yet grannies and six-year-olds are hardly the threat. Nobody matching that description hijacked a plane on 9/11, or set off a bomb on a train in Madrid in 2004, or blew up a Tube train or bus in London last year. Nor, for that matter, are there any among those detained here and in Pakistan over the alleged liquid bomb threat.
Is airport security so short-sighted that it can't see the difference between the sorts of people who present no risk, or at least a risk so small it is insignificant, and the sorts of people who might conceivably be on a suicide mission? For goodness' sake, let them select the appropriate people to search thoroughly and give the rest the routine once-over; that way, with hardly any extra risk, we might all have some chance of taking off on time.
It's only common sense. Even the most liberal-minded among us might well see the point, especially if we are about to take our families off on holiday abroad.
And it's not just airports: those police officers at Tube and railway stations, do we really expect them not to give priority to young Arab and Asian men? What sort of madness would it be if they were forced to devote exactly as much time to scrutinising the grannies and six-year-olds? That sounds a bit like, er, political correctness gone mad.
Well, beware common sense. Start by remembering that William Hague's Conservative Party used to advertise itself with posters showing the likes of Hague, Ann Widdecombe and John Redwood above the slogan "The Common Sense Revolution". And if that's not enough to put you off, try being scientific.
Most scientists have a revulsion for common sense. Einstein described it as nothing more than "the collection of prejudices acquired by age eighteen", and the biologist Lewis Wolpert has observed: "I would almost contend that if something fits in with common sense it almost certainly isn't science."
The point is an obvious one: if we trusted common sense we would still think the Earth was flat and the Sun sailed serenely over it once a day. Wolpert argues, in fact, that almost all scientific inquiry subverts common sense in some way. And where in common sense does it explain how water falls out of the sky as rain or how, before it falls, it hangs around up there as cloud?
Tom Paine's arguments for American independence were as sound as they were ground-breaking, but one thing they weren't, for 18th century people, was common sense. Just like e=mc2 in 1905, they were revolutionary; presenting them as common sense was Paine's sleight-of-hand.
Today, with passenger profiling, where common sense fails us is not on Einstein's point of prejudice, though there might just be a hint of that about. Nor is it on the practical points, often raised last week, that not all bombers are brown (though that is certainly a hurdle) and not all brown people are Muslim.
It fails because it pretends that queues at airports are discrete phenomena that happen, as it were, in test tubes, isolated from their surroundings. They are not. It is about 10 years since researchers studying stop-and-search started noticing young Asian men creeping into the picture. They had not been an important factor before, but now, in places, they were beginning to impinge on the statistics.
Britain had had a substantial Asian population at least since the 1970s, so what had changed? Perhaps Asian people had become acclimatised in some way, or perhaps it was a sign of generational shift. Who knows? But young Asian men were present in a new way, and as a result some were coming into contact with the police. It's hard to remember it now, but even before the attacks of 9/11 the police power to stop and search was extended so that the need for "reasonable suspicion" was waived.
With the use of the power so much easier, and with the change of mood since 2001, we hardly need to be told what followed: Asian people are probably three or four times more likely to be stopped and searched than white people, and after a bomb or a bomb scare it can go up to 12 times - and that is just what is recorded. Think back to the airports: none of us likes being delayed, questioned, forced to turn out our pockets, open our bags and explain our movements, even when we know it is happening to everyone else who is travelling, and even when those doing it to us are polite. That much has been obvious in the past fortnight.
How much worse, then, when it happens to you at, say, Euston Station and you are the only one experiencing this on the whole, crowded concourse. How much worse when it happens two or three times a month, as you walk, drive or take a train, and when those doing it aren't always polite? And if you complain, you get to go to the police station to cool down, and you go on the list to be stopped more often.
Next, imagine you are accust- omed to experiencing occasional casual racism from your fellow-citizens, you view your government's policy in the Middle East as anti-Muslim and you are offended by the way ministers talk down to your community. And now the suggestion is that there should be a policy for isolating and delaying you at airports, while the white grannies and six-year-olds march by.
No rational person would claim today that the Government deliberately wants to make enemies of young Asian men, but if you were one of them and you obeyed the common sense that is supposedly good enough for everyone else, that is what you might well believe. And who wants that?
Brian Cathcart is assistant editor of the 'New Statesman'Reuse content