The answer, I believe, is that the Western political and intellectual classes adopted liberalism as their orthodox belief some hundreds of years ago.
Liberalism is the idea that we are human because we can use our own individual reason and will to shape who we are. The idea, in other words, is that to be fully human we must be free to define ourselves according to our own will and reason.
Liberals have therefore sought to increase individual "freedom" by removing any impediments to the self-defining individual. And, unfortunately, traditional nationalism is one of these impediments.
Why? Because traditional nationalism is based on ethnicity. What binds a people together as a nation, in the traditional understanding, is some kind of common heritage, whether it be a shared ancestry, culture, language, religion or history.
Belonging to such a national tradition is an important part of our self-identity: of our sense of who we are. But it's something that is inherited, and not chosen. So it offends the first principle of liberalism: that we must be self-created by our own reason and will.
For people who are not liberal intellectuals, this might all sound a little unfamiliar. But listen to intellectuals themselves, and you quickly discover the importance of such concepts.
For instance, one of the most influential intellectuals on the issue of nationalism is Michael Ignatieff. He is a Canadian born writer and a Harvard professor, who made a BBC TV series and wrote a book on nationalism in the 1990s.
You can see the influence of liberal theory even in the way Michael Ignatieff chooses to define nationalism. He distinguishes between a "good" nationalism, which he calls civic nationalism, and a "bad" nationalism, which he calls ethnic nationalism (which is effectively traditional nationalism).
In defining the "bad" form of nationalism, Professor Ignatieff writes that "Ethnic nationalism claims ... that an individual's deepest attachments are inherited, not chosen. It is the national community that defines the individual, not the individuals who define the national community."
Why define ethnic nationalism in this way? Because it highlights what is wrong with ethnic nationalism, when liberal first principles are considered.
That's why ethnic nationalism is here defined negatively as something "inherited, not chosen" and as something which "defines the individual" rather than being defined by the individual. These features of ethnic nationalism are unacceptable to the liberal ideal of the self-defining individual, and so are emphasised in Professor Ignatieff's definition.
It's much the same when Professor Ignatieff defines the "good" form of nationalism, namely civic nationalism. He writes that,
According to the civic nationalist creed, what holds a society together is not common roots but law. By subscribing to a set of democratic procedures and values, individuals can reconcile their right to shape their own lives with their need to belong to a community.
In this quote, civic nationalism is defined positively, in terms of liberal first principles. Civic nationalism is good, by definition, because individuals aren't connected by (unchosen) "common roots", but merely by an agreement to live within a democratic system. So, rather than being shaped by something inherited, they are free to "shape their own lives".
Michael Ignatieff is therefore acting consistently with liberal first principles when he rejects traditional ethnic nationalism in favour of civic nationalism.
And what can we say about civic nationalism? Can a common commitment to democratic politics give people an adequate sense of national community?
Most conservatives would probably find such a form of connection to be superficial compared to traditional ethnic nationalism. And, in fact, Michael Ignatieff concedes this. He admits that traditional nationalism's "psychology of belonging" has "greater depth than civic nationalism's".
This is not such a problem for Professor Ignatieff, as he is not interested in national belonging anyway. He confesses that he is not really a nationalist of any kind but a cosmopolitan, and that the point of civic nationalism is merely to help maintain social order.
He describes his overall outlook as follows:
It is only too apparent that cosmopolitanism is the privilege of those who can take a secure nation-state for granted ... The cosmopolitanism of the great cities - London, Los Angeles, New York, London - depends critically on the rule-enforcing capacities of the nation state ...
In this sense, therefore, cosmopolitans like myself are not beyond the nation; and a cosmopolitan, post-nationalist spirit will always depend, in the end, on the capacity of nation-states to provide security and civility for their citizens.
I am a civic nationalist, someone who believes in the necessity of nations and in the duty of citizens to defend the capacity of nations to provide the security and rights we all need in order to live cosmopolitan lives.
This could hardly be more clear. Civic nationalism is not supposed to provide a form of national belonging. It's real purpose is to uphold the nation state, so that we have the order and security "to live cosmopolitan lives".
So the logic of the situation goes something like this. Conservatives like traditional ethnic nationalism because it's an important part of our self-identity and helps us to feel rooted within a particular tradition.
Liberals, though, are ultimately led to reject such nationalism, because they want to be self-defined through their own reason and will, rather than through an unchosen form of nationalism.
That's why liberals talk about traditional nationalism negatively as something limiting to the individual, as when Michael Ignatieff reminisces of the 1980s that,
With blithe lightness of mind, we assumed that the world was moving irrevocably beyond nationalism, beyond tribalism, beyond the provincial confines of the identities inscribed in our passports, towards a global culture that was to be our new home.
It is no accident, that Professor Ignatieff dismisses traditional nationalism here because it "confines" our identity to something "provincial". Anything which impedes our own self-creation will be regarded as something small or limiting or constraining by a liberal.
So what is the task for conservatives? Obviously, it's not enough to complain to liberals that they are creating individual rootlessness. For liberals, this is not necessarily a bad thing - Michael Ignatieff, for instance, is happy to defend the existence of what he unselfconsciously calls "rootless cosmopolitans".
The Canadian columnist Mark Steyn made a similar point recently when he observed that,
As an idea, the multicultural welfare state is too weak to have any purchase on us; that, indeed, is its principal virtue in the eyes of its few fanatical zealots ... politically speaking, it's an allegiance for those who disdain allegiance.
It is, to put it the Steyn way, no use complaining about weak forms of national allegiance to people who view national allegiance negatively as a constraint.
What we have to do is challenge the philosophy which leads people to think of nationalism as something limiting to the individual, rather than as a fulfulling part of our self-identity.
And this means challenging liberalism as an orthodox belief among Western intellectuals.
(First published at Conservative Central, 15/04/2004)