The choice for Britain in Europe is not what most people think it is. Most people think the choice is whether or not to swap the pound for the euro in order to jump aboard a Franco- German Eurostar train, timetabled from Brussels and heading for Union station. Europhiles say that although we will share sovereignty, we will gain power and prosperity; Europhobes say we will lose sovereignty without gaining either power or prosperity. This picture is ten years out of date - and it was inaccurate even then.
A better metaphor is that of a house. The EU-rope of 15 members is still a house largely designed by French and German architects. We have lived there for more than a quarter-century, as part of a residents' co-operative, and we have had some influence on the interior design. Margaret Thatcher, for example, was instrumental in having a number of rooms knocked together, producing an open-plan arrangement called the single market. But we - meaning the British, but more especially the English - have never been quite comfortable there. We still feel it is really someone else's home. This feeling has been exacerbated because, throughout most of this period, the French and German architects, rather ostentatiously proclaiming themselves a "couple", have repeatedly insisted that nothing important can happen without them.
What most people have not noticed is that the house has changed in the past decade, and is about to change even more. The residents' co-operative has already agreed - at a special meeting in Nice - that the house will nearly double in size. Voting cards have been assigned to no fewer than 12 applicants for membership. Moreover, all the residents now agree that such a large extension - or "enlargement", as they call it - will mean redesigning and rebuilding the whole house and changing the way it is run.
Here is an opportunity for Britain, one of the richer residents, to make the place more to our liking. As we saw in Nice, the Franco-German couple are not what they were. The German architect is more independent and more powerful than he was before 1990; he feels that he has paid off the debts and moral obligations that he ran up in a disastrous earlier phase of his life; and he is not as committed to his French partner as he used to be. Meanwhile, more recent arrivals such as Spain have grown in strength and self-confidence, while the smaller residents resent being pushed around by the bigger ones. So when it comes to the new design, there are new alliances to be made, and new arguments to be won.
Perhaps this metaphor has become overextended - as some fear the house itself may do. But it does help to focus attention on the real European choice for Britain, which is whether or not we want to be fully involved in the redesign and building of this new, larger house, over the next 20 years.
Nobody knows whether and how a community of 27 and more member states can work. Only a dwindling minority in Europe believes that it can work as a federal superstate, with its own European government, parliament and courts. The direction in which the EU has been developing in recent years is actually away from that. With the notable exception of monetary union - that son-of-Maastricht - the growth areas of community action are mainly intergovernmental: defence and security policy, immigration and home affairs. If anything, it is the power of the Council of Ministers that has grown, relative to that of the commission.
Yet the question remains: how can this complex, hybrid structure continue to function without a total blockage caused by the conflicting interests of so many member states? Many would say the Nice summit has already produced a minimalist outcome - and that was with the conflicting interests of just 15 states. At the same time, how can a redesign secure more democratic control? For there is no doubt that there is a crisis of confidence in EU institutions, not just in Britain but right across EU-rope. So the daunting triple task is to make the EU simultaneously larger, more effective and more democratic.
A number of competing visions have been canvassed - notably by Joschka Fischer, the German foreign minister, Jacques Chirac, the French president, and Tony Blair, in his October 2000 Warsaw speech. The argument will develop over the next three to four years, culminating in a new intergovernmental conference already scheduled for 2004, and linked to the first eastward enlargement, to take in countries such as Hungary, the Czech Republic and Poland. In short, the formative debate will coincide with what seems likely to be Tony Blair's second term in office.
This debate will be about institutional structures and efficiency. It will be about democracy: does democracy in Europe, as Blair insisted in Warsaw, still primarily derive from the nation states, and, if so, how can that kind of democratic legitimacy be reinserted into the European project? It will also be an argument between (simplifying greatly) two broad visions of the way Europe should go. One is a Napoleonic vision of an etatiste, bureaucratic but also welfare- and social-security-providing Europe, a fortress Europe, which avowedly aims to become a rival superpower to the United States. The other is a liberal, Atlanticist vision of an open, flexible, free-trading Europe, which regards itself as a self-confident partner rather than a rival to the United States.
My reading of the present European situation is that the argument is up for winning by the - liberal and Atlanticist - second school. The movements of opinion in Germany, in the business community and among the younger generation all over Europe all point to this conclusion. But the argument can probably only be won decisively for this school if Britain is fully involved in it, as it has been, for example, in the design of the fledgling European security and defence identity and especially the European rapid reaction force. To be sure, American military and political leaders have expressed concern about its "decoupling" from Nato - but not half as much as they would have done if Britain had not been involved in its design from the outset.
However, can Britain be fully involved in winning that argument, and redesigning the larger house, unless it joins the EMU? Increasingly important economic decisions will be made in the Euro-X - currently, Euro-12 - group of members of the EMU, rather than in the Economic and Financial Council of the EU. And, rightly or wrongly, both for British and for Continental European opinion, EMU membership has become the symbolic test of Britain's European commitment. But the convergence of our economies is not clearly established and EMU, even in its present form, is likely to face great stresses over the next few years.
The real choice for Britain is thus whether to take a historic gamble. The gamble is that, by fully engaging in EU-rope, we can change it into something more like what we think it should be. Only if we were consciously committed to this larger political gamble would it make sense to take the smaller gamble that is membership of the EMU.
Some would say that this suggests yet another British illusion about our role and power in Europe. The reason it may not be true, this time, is that there are deeper forces which have already begun moving EU-rope in this direction since the end of the cold war. On many issues, the scales are finely balanced, and Britain's still significant weight could tip them in the right direction.
There is, in my view, a realistic chance of success. However, there are two other possibilities. The first is that we fail to persuade our fellow residents to adopt a design of the house with which we can live - and which we feel is better for the house as a whole. The second, which one has to state quite clearly, is that the whole house starts to fall apart, like some 1950s tower block. For no one has ever done this before. There have been smaller groupings of states in European history that have lasted 30, 40 or 50 years. There has never been such a large grouping of European states that has endured for long, and certainly not - as this one must do - on the basis of consent rather than hegemony.
A rational British choice would be based on informed guesswork about the probability of these three outcomes. This would be a difficult enough exercise at the best of times, but it is made virtually impossible by the extraordinarily distorted and partial picture of Europe that most educated Britons receive from their newspapers, television and radio - with the newspapers being much the worst. Whatever choice we finally make about the gamble of engagement, one choice we should most certainly make is to start seeing Europe as it really is.
Timothy Garton Ash, a fellow of St Antony's College, Oxford and of the Hoover Institution, Stanford, is the author, most recently, of History of the Present: essays, sketches and despatches from Europe in the 1990s. This article appears in Martin Rosenbaum (ed): Britain and Europe: the choices we face, just published by OUP (£8.99)