When Al Gore was a young boy on summer holidays at the family farm, he would amuse himself by hypnotising a chicken. By circling his finger around its head and making sure its eyes were following, he would immobilise the bird with fear.

“There’s a lot you can do with a hypnotised chicken,” he writes. “You can use it as a paperweight or you can use it as a doorstop and, either way, the chicken will sit there motionless, staring blankly.”

Much the same, he argues, has been done to the American people over the past six years with George W. Bush as the young boy and Karl Rove, his chief political strategist, as the finger. Fear, whether it was talk of “mushroom clouds” coming out of Saddam Hussein’s Iraq or the use of terror alerts at critical junctures in the political calendar, has been Mr Bush’s preferred way of “manufacturing consent”.

In this, the Bush administration has been assisted by the ubiquity of television, which the former vice-president sees as an idiot box that judges news by the cynical maxims: “if it bleeds it leads” and “if it thinks, it stinks”.

The decline of reading and writing, which Gore likens to the “calisthenics of democracy”, has made chickens of us all. The opposite of fear, he says, is reason. “It might be called American Democracy: The Movie,” Gore writes. “It looks and sounds almost real, but its true purpose is the presentation of a semblance of participatory democracy in order to produce a counterfeit version of the consent of the governed.”

At different points in The Assault on Reason one is tempted to see it as a thinly disguised manifesto for Gore’s entry into the presidential race later this year, as a cry of rage against Mr Bush, whom half of America believe stole the 2000 election from Gore, or as the hyperactive musing of a man who left public office too soon.

Gore’s book may be all of these things. But it is also a coherent and passionate plea for Americans to shake themselves out of what the author semi-convincingly paints as an unholy blend of acute jitteriness and thoroughgoing ignorance.

Americans frequently complain about the declining quality of Congress. But when only 15 per cent of voters are able to recall the name of one of their candidates and just 4 per cent can recall two names then arguably they get what they deserve.

Likewise, a majority of college students were unable to recognise the following statement in the Declaration of Independence: “We hold these truths to be self-evident, that all men are created equal.” Only 43 per cent of Americans could name even one of their nine Supreme Court justices.

“The truth is,” he continues, “that American democracy is now in danger – not from any one set of ideas, but from unprecedented changes in the environment within which ideas either live and spread, or wither and die. I do not mean the physical environment; I mean what is called the public sphere, or the market place of ideas.”

Less convincing is Gore’s starry-eyed rendering of America before television supplanted the written word and before Mr Bush took office (the fact that the latter took place 40 years after the former makes for a constant tension in his argument). In essence, it was a Republic of Reason. “For all of America’s shortcomings in the past, we did usually strive to honour truth and reason,” he writes.

It would be easy to dwell on the shortcomings of Gore’s idealised accounts of the past and his preoccupation with rekindling the Roman virtues of a “well-informed citizenry” – this time through the internet – that reaches decisions after careful deliberation of what is in the public interest. Easy, but also unfair.

For Gore also provides a diligent and often devastating account of the damage the Bush administration has wrought to the American constitution and its implications for the health of democracy. He convincingly links the public’s half-informed apathy to Mr Bush’s success in playing fast and loose with the separation of powers.

Whether it is Mr Bush’s promiscuous use of “signing statements”, in which he effectively crosses his finger behind his back when putting his signature to a law (which, say, outlaws torture, upholds habeas corpus, reaffirms the right to privacy or virtually any other sacred tenet of American democracy), or the White House’s disregard for the constitutional rights of Congress, Gore’s case against America’s 43rd president is hard to refute.

Meanwhile, barely half of Americans believe the president is required to abide by Supreme Court decisions with which he disagrees, according to a survey last year by the University of Pennsylvania. So much for the separation of powers. “We have reached a point where we can no longer recognise our country when we look in the mirror,” says Gore. But how many people are looking?

The writer is the FT’s Washington bureau chief