Nearly 75 years ago, the French writer Julien Benda published his now-classic essay The Treason of the Intellectuals. Benda argued that the true intellectual, like Emile Zola during the Dreyfus Affair, defended "universal" values, while nationalist opponents instead embraced the particular values of France. For Benda, the choice was clear: the imperative of justice and transcendental truths on the one hand; reasons of state and national myths on the other.

The latest essay by one of France's reigning intellectuals, Régis Debray, suggests the nationalists have just won over one of their former opponents. His Eloge des Frontières, just published by Gallimard, is a superficial work. But there are depths to the superficial - especially when it occurs in a charged context. This is certainly the case for France today, which is more divided than ever over the issues of immigration and national identity.

A young philosopher chasing revolution, Debray first catapulted into public prominence from the forests of Bolivia. In 1967, he was arrested by the Bolivian authorities, found guilty of associating with Che Guevara's guerilla movement and sentenced to a thirty-year prison term. When his case became a cause célèbre, Debray was released. Few thinkers, it seemed, took more seriously the call for political engagement than Debray.

Debray became the poster child for intellectuals without borders. But world revolution has become so yesterday; devolution is today's ideological flavor. Rather than the specter of communism, what now haunts the world is the ideal of a world without borders. Debray does not give those who thought this was true only for speakers of Esperanto the time to weigh his observation. Instead, skipping lightly in a few pages over millennia of human history, Debray insists that rather than boldly going where no people has gone before, we need to return to the past.

It is the past, he argues, that reminds us that frontiers guaranteed the sense of the sacred; that frontiers alone safeguard the unique character of a people. To cite counter-examples, ranging from the Jews to the Roma to the Acadians, in order to dispute Debray's claim is pointless. History must not get in the way of his poetic metaphors. Thus, for Debray, the French identity is the result of "seventeen centuries of sedimentation." It is the lay of the land and the laying of a table; what never lies are the soil and moeurs cultivated by a people.

But metaphors are complex. What do we do with those "elements," for example, recently introduced to the process of "national sedimentation"? Are they less French, especially if they do not recognize the same landscapes and table manners that Debray celebrates? In his riffs, Debray variously compares the border to a strainer, to human skin, to an "interface between the organism and the external world." It is, in short, a filter. These metaphors are certainly more generous than the border as a wall or rampart. But they raise a crucial question: what, precisely, does France seek to filter out?

While Debray does not bother to answer this question, many of his more conservative contemporaries do bother. Their answer has its roots in a writer Debray often echoes, the influential fin-de-siècle politician and nationalist Maurice Barrès. In his novel The Uprooted, Barrès explored the effect of abstract reason and universal standards, taught by professors who dined on Kantian idealism rather than Alsatian sausage, on the nation's youth. The result, for Barrès, was a decadent people and national decline.

Debray is certainly not an irrationalist, much less an anti-Semite, as was Barrès. But the two writers share the same obsession with borders. What Barrès meant by cosmopolitanism, Debray means globalization; what Barrès feared in Kantian idealism, Debray sees in corporate capitalism. If the land and the dead, as Barrès famously declared (and Debray clearly believes), is the stuff of the French nation, what happens when by malls and McDonalds - or, indeed, Muslims - overrun them?

Here is the rub: for France's extreme right, the enemy is not just globalization, but also "Islamization." Marine Le Pen, heir apparent to the xenophobic and protectionist Front National, hammers at these two issues in her public appearances. Like Debray and Barrès, Le Pen decries the leveling effect of global economic and cultural forces. But like Barrès, she also recoils at the presence of the "other" that threatens the organic purity of the French nation. For Barrès, the "other" was the Jew; for Le Pen, it is the Muslim. Debray does not identify a specific "other," but his notion of a filter anticipates his or her existence.

In the Treason of the Intellectuals, Benda asked what would "happen to a humanity where every group strives more eagerly than ever to feel conscious of its own particular interests?" A "child can give the answer," he replied. Surely Debray knows the answer as well.