It is time, writes Robert Kagan, to stop pretending that Europeans and Americans share a view of the world, or even that they occupy the same world: "Americans are from Mars and Europeans are from Venus." His provocative thesis has two strands. First, that growing differences have emerged between the two continents since the Second World War. Powerful America lives in a "Hobbesian world of threats and disorder", has a low tolerance for threats, and is not afraid to act unilaterally to eliminate them. Meanwhile "weak Europe", scarred by the experience of war, has renounced power politics and retreated into a "Kantian world of perpetual peace" where order is guaranteed by self-enforced rules of behaviour.
The second strand to the argument is that this divergence will destroy the "west": the double deal which saw Europe's paradise underwritten by American force has passed. The determination of successive presidents to retire European countries from power politics has waned; the Bush administration sees Europe as a weak free-rider rather than an "overheated incubator for world wars". Further, Europe's importance as a bulwark against Soviet communism has disappeared, and with it, too, the American need to protect the coherence of the west. The events of 11 September brought home what the end of the cold war made inevitable: Europe's further retreat into strategic irrelevance, and America's entrenchment of its global hegemony.
Paradise and Power is energising to read: subtle, well written, but totally infuriating. Every page demands a response; my own copy of the book soon had more red pen than printed words on each page. Many commentators will no doubt point out that Kagan's starting premise is doubly false: it is neither clear that America is always more bellicose, nor that there are clear European and American positions on the use of force. Kagan himself admits that Bill Clinton behaved in a very Venusian way over Kosovo, while ten European leaders have lined up behind Bush's Martian line on Iraq. What seems to be more important is the perception of threat in each case. The Balkans are a long way from small-town America. At the same time, it is natural that Europe, which was not attacked by al-Qaeda, should have a more sanguine response to Iraq - after all, even the Bush administration wanted to rely on containment before 11 September.
But this banal dissection of facts is only a partial refutation of Kagan's thesis - and moreover it is disingenuous. There does seem to be a gulf between multilateral Europeans and the more unilateral American foreign policy community - Democrat and Republican alike. This might be disguised by there being many countries that value their bilateral relationship with the lonely superpower more than their policy on Iraq (a small, faraway country about which they know little) - but it is real.
Kagan ought to be taken to task at a deeper level: over his impoverished and outdated notion of power, and his complacency about US hegemony. The biggest challenge to his thesis - and to the idea of perpetual American hegemony - is less likely to come from another great power than from changes in the world.
One could fill entire libraries with books on how the biggest threats to our citizens come not from invading armies, but terrorists, climate change, drug-trafficking, population movement, or the erratic flows of the $1.5trn traded daily on the foreign exchange markets. But the growing evidence to support this does not fit easily into Kagan's state-dominated world. On the surface, it is possible to reduce these non-state threats to those that can be dealt with through Kagan's military power; this is a superficial trick. The campaign against al-Qaeda in Afghanistan may have been military, but to eliminate the cells of terrorists in Hamburg, Madrid or London will rely more on diplomacy than precision bombing. In this world, the weakness of American coercion will contrast with the power of European attraction. One need look no further than European and US policies towards neighbouring countries. The dangers are similar - drug-trafficking, large flows of migrants across hard-to-police borders, transnational criminal networks - but the European response of encouraging political and economic reform by holding out the possibility of integration into the EU has had more enduring success than the swift military interventions of the "Monroe doctrine".
Second, the rise of nationalism and education around the world means that actions and policies which have a ring of imperialism will get diminishing returns. America may be able to bully and bribe other governments into submission when it needs their support, but the transaction costs will get higher and higher each time. And even compliant regimes will find it increasingly tough to keep their hostile populations and civil societies under control - as the Turkish parliament's "no" vote demonstrated so clearly. This is the same parliament that has passed dozens of bills to make Turkey more attractive to the EU over the past few months. The sheer "in-your-face-ness" of US power invites hostility on a scale totally different from the feeling prompted by Europe's more sensitive "post-imperial" brand of diplomacy. While every American company, embassy or military base is a target for terrorists, Europe's relative invisibility allows it to spread its power without danger. To put it bluntly: even if there were people angry enough to want to fly planes into European buildings, there is no European World Trade Center to target.
Kagan would no doubt present the recent splits between "new" and "old" Europe as further evidence of European weakness. But it is also possible to portray the past few months as a sign of European strength. It is not popular to say this, but so far the accidental good cop/bad cop routine that Britain and France have developed seems to be working. Britain drags the US into global institutions, while France and Germany ensure that they follow due process. US power has been deployed to back up the United Nations, and Saddam Hussein will most likely either disarm himself or be disarmed in a way that is supported by international law. This could be seen as preferable to both the freewheeling unilateralism of US foreign policy in the 1980s that produced strikes on Libya and Grenada with no mandate, and the multilateral agreements to do nothing about genocide in Bosnia and Rwanda in the 1990s.
Naturally, this works only because it is not a deliberately orchestrated good cop/bad cop routine, but a genuine disagreement. However, it does show how Europe's diffuse, almost fuzzy power can have an impact - not just on the European accession countries but even on the hyperpower.
Kagan's book has been taken as a wake-up call for European leaders - but maybe it is George Bush who needs to make his mind up. Europeans have taken "a break from geopolitics" because they thought that the United States was engaged in a global project similar to theirs. But now this is being questioned on both sides of the Atlantic - and all bets are off as to how it will resolve itself. Ultimately, it boils down to an American decision about whether the US is going to continue to be a benign hegemon - or whether its impatience with others is so strong that it becomes the selfish superpower. If the US does go down this route, we will all be losers. Europeans might be forced to pay for their Kantian world out of their own taxes but the Americans will lose the unipolar world that is so celebrated by Robert Kagan.
Mark Leonard is director of the Foreign Policy Centre