Doctors need organs for transplant. How do they persuade people to commit to donation after their death? They might ask them to tick a box opting into organ donation. Or they might arrange for opting in to be the default condition and ticking the box means you opt out.

There's not much difference, you might think - but there is. In one experiment, ticking to opt in resulted in 42% of people agreeing to donate; ticking to opt out resulted in 82% agreement. The default condition nudges people to conform.

This has certain implications. For a start the idea that there is some high principle - the sanctity of the human body - behind widespread resistance to donation appears to be wrong. And, second, freedom to choose is not what it seems. People act in response to the default condition, not in answer to some higher rationality. To embrace the default is to belong and neither principle nor rationality can stand in the way of the need to belong.

Politically this is, at the moment, hot stuff. Both the Cameroons and the Obamistas are said to be reading Nudge in an attempt to discover how and when people should be gently manoeuvred into doing the right thing. The planet may depend on this, as may our health and pension prospects. People can be nudged into saving energy, stopping smoking and saving more. Nudging is the new politics. Richard H Thaler and Cass R Sunstein - two Chicago academics - have hit publishing pay dirt with an idea whose time seems to have come.

It has come because of the failure of two older ideas. The first was post-war, top-down, bureaucratic paternalism - still, bizarrely, kept alive, if only just, by Gordon Brown's wretched regime. This depended on the economics of John Maynard Keynes and assumed that, ultimately, clever people in the government knew best. The second was neo-liberalism, the cult of the free market that, under Ronald Reagan and Margaret Thatcher, became the orthodoxy of the West. This depended on the economics of Milton Friedman and assumed that, ultimately, people, through the workings of the market, knew best. Both had their successes and both failed. With Nudge, Thaler and Sunstein have written the textbook of the Third Way.

This third way precisely splits the difference. They call it libertarian paternalism. This means there should always be freedom of choice but there should also be nudges in the direction of doing the right thing. You can, for example, buy a Wattson, a device that tells you how much energy you are using in your home. It doesn't force you to turn off a light, but, somehow, observed by Wattson, you do.

The discipline that lies behind this is behavioural economics. Classical economics has always aspired to be a science. This is folly and yet still economists are given Nobel prizes for generating elaborate equations that describe nothing and predict less. People are not electrons, they're not even atoms. They don't do things that economists want them to do like, for example, “maximising their interests”. In their different ways, neither Keynes nor Friedman fully understood this. Behavioural economics embraces human irrationality as a given, not an unfortunate epiphenomenon. Thus Sunstein and Thaler begin from what people do, not what they should do.

Unfortunately, many of the things people do are downright weird. One study asked 40,000 people if they intended to buy a new car in the next six months. Car purchases in the group rose by 35% - just because they had been asked the question. In another experiment, people were placed in front of a bowl of Campbell's tomato soup and told to drink as much as they wanted. They didn't know the bowls were being refilled from below. A surprising number just kept on lapping it up until the experiment was stopped.

The message is that people are heavily influenced by context - ask a question, fill the soup bowl, and they will behave in ways that no rational analysis would have predicted. Sunstein and Thaler call the process of designing the context “choice architecture”. This will affect everything from what appears where on supermarket shelves to how government persuades people to save for their old age and improve their health.

This is all very well and, for the moment, more persuasive than the preceding economic fundamentalisms. But there is one big issue. These choice architects are going to be extremely powerful people under the Obamist-Cameroon dispensation. It looks as though we are all going to be manipulated all the time. Malign or stupid choice architects will inevitably find new ways of screwing us up, however well intentioned the bosses. Benign norms are implied by the authors but the mechanism for identifying and enforcing them is unclear. This leaves us back where we started politically.

But it's interesting stuff, you might think. Unfortunately, if you read the book you will change your mind. Although snappily packaged with its one-word title to get into the same market sector as Malcolm Gladwell's Blink, it is a very, very dull read, a dogged march through social policies with boring lists of what nudges should be imposed and how. Occasionally they startle - state-endorsed marriage should, they say, be abandoned and replaced by civil partnerships - but, when they do, their arguments are thin and, to my mind, off the point.

What the book needs is not more examples but more elaboration of the central idea. Clearly, this is a new way of making democracy work, but what are the implications of that? Also, the authors don't say enough about the relationship of nudging to advertising. However, much the government nudges people to eat better, the advertisers will always be out there telling them to fatten themselves to death. I am writing this in America, and I can tell you it's working.

Lenin, in between slaughtering peasants, would have seen the problem - “Who-whom?” he asked. Who is the nudger and who the nudgee? The new politics will be, as ever, the same old politics.

Nudge by Richard H Thaler and Cass R Sunstein
Yale £18 pp293 Buy the book from Books First £16.20 including free delivery

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