It is now generally accepted that French philosopher René Descartes was right; humans can be relied on to do the sensible thing eventually. "Cogito ergo sum", he said "I think, therefore I exist". And with a little carping from the existentialists, stage left, he was right. We are essentially rational beings. So why does this not apply to politicians?

What brings this home right now is the extraordinary fall in the popularity of British Prime Minister Tony Blair, who, by rights should be striding the world stage in a manner not unlike fellow Briton David Beckham.

Blair overcame popular opinion to fight an unpopular war alongside the US, a remarkable achievement not to mention a remarkable decision for a left-of-centre politician.

Instead he is reduced to visibly reddening in front of the television cameras when questioned about the suicide of scientist David Kelly.

For those who have not been watching late-night television, Kelly's death has created a storm in the UK following his role in a heated debate between Blair and the national broadcaster, the BBC.

During the runup to the war, the BBC reported that "an intelligence source" had said the British government "sexed up" the evidence on Iraq's weapons of mass destruction.

Kelly, the source, was caught up in various investigations over the affair. He apparently could not take the pressure, and slit his wrists while on a country walk, an odd way and odd place for a scientist to kill himself.

From a political point of view, the really strange bit is Blair's approach to the issue. Almost six months after the war and no weapons of mass destruction in sight despite frantic searching, it seems silly to persist in the argument that the war was justified because of their purported existence.

It is especially odd as this argument is only one of many that might justify the war. The most obvious is that removing a brutal and dangerous dictator is not something that ought to put you in the dog box.

This argument might not convince those implacably opposed to the war, or even those sticklers for international law, which requires an imminent threat, but it does have the advantage of being broadly valid.

But that was not the line of argument that Blair's government pursued. Before Kelly's death, it reacted indignantly and haughtily to the claim that it had "spurned" the facts.

Central in this debate is Blair's press spokesman, Alastair Campbell, who was full of righteous indignation. Unfortunately, his conceit is undermined by his reputation for being the ruthless master of "spin".

While reporting in the UK, I experienced first-hand the Blair government's propensity for combining an underlying hostility to the media with the righteousness of a higher calling. It is an odd and interesting posture: elusiveness posing as rigour, and rigidity posing as diligence. South African newspapers used to post journalists to the UK with the unspoken agenda that they were there partly to learn how things should be done. All too often, the result was the opposite. I came home yearning for the friendly conscientiousness of the South African government's press officers, despite their occasional cluelessness.

The best example I can provide on the Labour government's approach to the media has to do with an old story about the Lockerbie bombing, which has long since been resolved. Then British foreign minister Robin Cook held a press conference after a step forward in behind-the-scenes negotiations with the Libyan government, and called for the assistance of "those other government leaders" involved.

As then president Nelson Mandela had been intimately involved, I called the foreign office press officer to ask if those "government leaders" included Mandela. Fair question I thought; perhaps even so obvious it would seem odd than I had even bothered to ask.

But, instead, I was met with rudeness and hostility, and was told rather shortly that "we do not intend going further than our original statement".

It wasn't a statement, I said, it was an off-the-cuff response to a question at a press conference.

No matter. Correctness was clearly more valued than being informative. Later that day, the US government confirmed Mandela was involved.

Blair's approach to the media has always bordered on hostility, so the fact that the argument about spin has escalated now is hardly surprising. It was bound to happen sometime. But why adopt this approach at all?

I'm not sure of the answer. But my suspicion is that it has to do with the exception that proves Descartes's rule. Politicians often tend to put ideology above rationality, because being an ideologue is what gives politicians purpose.

This same tendency is reflected in may ways in SA: in the AIDS debate; in the point-blank refusal to consider that Deputy President Jacob Zuma may have done something wrong; in the obsessiveness about quiet diplomacy in Zimbabwe. Meanwhile, the populace looks up at politicians flying by in their space ships, and meekly asks for reasons. Or at least reason.

With acknowledgements to Tim Cohen and the Business Day.