John Dunn watches the American dream become a global nightmare.

The first ambition of After the Empire is to restage a prophetic coup. In 1976, Emmanuel Todd, a youthful French demographer working at the Institut National d'Etudes Demographiques, in Paris, published an essay on the Soviet Union, La Chute Finale , that confidently foretold its rapid and permanent collapse. He reached this assessment by focusing on its birth and mortality rates. The collapse that duly followed scarcely corresponded, in either its apparent causes or its political dynamics, to any script suggested. But it did ensue, and still shows at least elements of finality.

After the Empire is a work of greater political engagement, excoriating the global impact of an America that has passed with bewildering rapidity from dream ("The world had a dream...") to nightmare, and calling down on it a doom almost as rapid and every bit as fulfilling.

Given its prophetic success, La Chute Finale probably sold fewer copies than it deserved. But even by this stage, After the Empire has more than redressed the balance, being already a bestseller in France and Germany and promising to fan out into at least 24 other languages, including Arabic, Catalan, Croatian and Bulgarian. It is clear that this is very much what Todd had in mind. His intellectual and social reference group, as he makes clear at the outset, is a set of relatively recent American bestselling writers - Henry Kissinger, Zbigniew Brzezinski, Samuel Huntington and, above all, Francis Fukuyama. Some of these writers, for better or worse, have been important historical actors in their own right.

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But what they have in common is that they have placed their minds unstintingly in the service of the empire, and profited handsomely from sharing their wisdom with a mass audience, achieving Machiavellian, or perhaps post-Machiavellian, careers as all-purpose consultants on how to seize global opportunity or handle global recalcitrance. After the Empire reverses the angle of incidence; and Todd offers himself, at least in the bookstore, as counter-consultant on behalf of the menaced globe. This is a relatively familiar Parisian role, if seldom previously essayed by a demographer. The scale of diffusion the book has already achieved is more than adequate testimony to the levels of demand for the service. What will global purchasers get for their money?

As imperial consultants have found across the millennia, the perspective of empire is none too clear or stable in the first place. But the perspective of the menaced globe is even less clear and utterly unstable, devoid even of any obvious principle of stability. This is not the sort of consideration to slow Todd down. But it might give his purchasers occasion to wonder quite what it is they are being sold. A short answer is a work of overweening self-assurance, unruffled condescension and stupefying demerit.

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The force of La Chute Finale came from its focus on one aspect of the Soviet Union, the significance of which the author was well placed to recognise in his professional guise. Even by Parisian standards, Todd sets a high value on his own insight and does not shrink from pronouncing on the largest of themes. But it is unlikely that it would have occurred to him in 1976 to address the globe on its own behalf quite as expansively and hastily as this. What has speeded him up and freed him from some of his inhibitions is less the lure of a vast and voracious market than a degree of involuntary identification with that market's hunger: less an irrepressible habit of interpreting the world than a keen desire to change it. You can see the setting of that identification (the road to Baghdad) neatly in a witty recent column in the Financial Times by Michael Skapinker: "All over the world, kids wear Nike, listen to Beyonce, eat McDonald's - and hate America." Skapinker's point is that globalisation is better at dispersing products than at homogenising culture or cementing inter-cultural affection. But it would be hard to improve on his formulation of the briskness of America's glissade from global dream to global nightmare in the postcommunist epoch conjured up by Todd's earlier prophetic triumph.

America under George W. Bush, as Todd presents it, is uncouth, dangerous, malign in its purposes and hellbent on carrying these out at other people's expense. Hence Todd's reference to empire and the opportunity for the US to get its own way over anything it feels like anywhere in the world and at any time. For oneself, omnipotence is not an unattractive prospect (though, like Midas' touch, it would no doubt prove disconcerting or even self-contradictory in practice). But omnipotence in anyone else is a brutal strain on the nerves. The good news Todd offers is that America is not going to get what it wants: that it is far from omnipotent, little more than a paper tiger.

Many of his grounds for this conclusion are quite right. In the first place, no human has ever been able to get everything they want, even from and through other human beings, in any setting for any length of time. In the second place, the limitations of the state as a structure through which to focus and enforce purpose within its territory are multiplied many times over in any venture to extend them protractedly beyond its own territorial limits. If you do not rule directly and on terms that equip you to go on doing so, you will have to rule indirectly on whatever terms you can elicit. As all imperial rulers have discovered in due course, it requires considerable selective attention to view these terms with equanimity, and even more intense selectivity to view them with pride. This is scarcely a point that needs pressing today in Iraq.

But Todd's principal sources of reassurance are less commandingly captured, and his judgements often wholly unconvincing. The most immediately consequential is his emphasis on America's economic vulnerability through its vast trade deficit. This is indeed relatively novel, and it must also be massively unstable in ways that may be enacted at any time. But it is wrong to see in it merely a vulnerability of the economy of the US, since what makes it possible are the growth strategies and assessments of the security of ways of storing the wealth of those who organise the most dynamic or industrially potent economies in the world. If the Chinese, Japanese and Koreans stop buying dollar assets, the Americans will be in dire trouble; but so too, all but instantaneously, will virtually everyone else. By the time the smoke clears, a good decade of most people's lives will have gone appallingly astray; and who knows what other nightmares will have burgeoned.

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Todd rejects Alan Greenspan's Panglossian vision of a world economy and an American economy blithely at ease with one another, and both in some sense ultimately under human control. He mocks the compulsive profligacy of America's consumers, and the hollowed-out industrial sector, producing little that others need but films, logos and heavy armaments, which conspicuously fails to fund their purchases. But the counter-economy that he offers the globe - an industrial protectionism centred on Germany, France and Japan - will seem politically premature and economically superannuated in many other parts of the world (China, Korea, Taiwan, India, Brazil). If and when the big crash comes, this counter-economy may simply arise anyway. But the transition to it will not be agreeable; and only the irredeemably audacious would contemplate launching on it in its own right.

Other elements in the global counter-empire also look suspiciously Gallic: not just sufficient and rationally modulated natality, but also a huge Eurasian industrial protectorate, pouring out real goods from behind its lofty tariff walls, and shielded by its very own force de frappe , moving magisterially beyond the democratic epoch dictated by mass literacy to a new oligarchy and a steeper class pyramid that expresses the novel power of the super-educated: Gaullism on a bicontinental scale. The specification of the recipe is startlingly uneven - all the way from the mutterings of Nostradamus to gnomically intriguing text messages from an intermittently practising demographer. Indeed in places, the text itself appears mildly corrupted. Is the diagnosis that America, in face of the new Greater Eurasian Co-Prosperity Sphere, will at last be forced to live like other nations, "reigning in its huge trade deficit", an aphoristic formulation of Todd's central intuition, or is it simply a spelling error? In other places, the guiding assumption seems antediluvian. Can it really be true that the vulnerability of America's empire (if that is what it is or means to be), best evinced in the indiscretion of its present economic policies, resides fundamentally in its being geographically so peripheral, or that Eurasia's coming counter-hegemony is, in turn, guaranteed by its being "closer to the geographical center of the world"?

As self-appointed global defender, Todd is at his least reassuring not in the role of economic adviser, but as guide to the due nurturing and use of military hardware. If you are considering buying this book you should examine carefully Todd's discussion on pages 124-125 of the relationship between America's military power and the uses to which it chooses to put this in defending its economic prosperity on the one side, and Russian anti-aircraft capabilities on the other. In my view, anyone who thinks the latter form the sole surviving barrier to an American world domination imposed by aerial bombardment needs to think again from the start.

John Dunn is professor of political theory, University of Cambridge.

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