Dramatic as it has been, the failure of the West to find an adequate response to militant nationalism in Bosnia in the 1990s is nothing new. As Ernest Gellner reminds us in Nationalism, it was the Versailles peace conference in 1918 that first gave real-world sanction to theories that had been percolating in academic and literary circles for almost a century. Far more significant than the details of the peace settlement, writes Gellner, was its overall result: "The system of states set up at Versailles, in the name of the principle of self-determination, was appallingly fragile and feeble. It collapsed at the first storm." And we have been struggling to put the collapse aright ever since.

Recent decades have seen a profusion of academic studies of nationalism and its origins. Most of this work defies ready categorization, but much of it relates to the debate between the primordialists -- who argue that the roots of nationalism lie in man's ancient past, if not in his genetic wiring -- and the modernists or constructivists, who make some variant of the case advanced by Elie Kedourie in the first sentence of his book on the subject: " Nationalism is a doctrine invented in Europe at the beginning of the nineteenth century."

Ernest Gellner, director of the Center for the Study of Nationalism in Prague when he died in 1995, is among the most distinguished of the modernists. Gellner is at pains, though, to differentiate himself from Kedourie (once his colleague at the London School of Economics), whose formulation he finds too simplistic. Other students of nationalism, notably Benedict Anderson and the journalist Anatol Lieven, have leveled the same charge at Gellner himself, but with little justification, judging by the present book, which gives full weight to nationalism's potent appeal: "The intensity and depth of feeling" it arouses, Gellner writes, is precisely what cries out to be explained.

Gellner himself defines nationalism as "a political principle which maintains that similarity of culture is the basic social bond." It has not arisen everywhere and in all ages; only when and where "men wanted the boundaries of social units and of cultures to converge." In the agrarian age, rigid social hierarchies, essentially similar from one polity to another, defined men's place in the world. While decidedly unwieldy and less than enlightened, these feudal pollties had the virtue of being free of nationally or ethnically motivated conflict.

As the agrarian age gave way to scientific-industrial society, and the hierarchies that had kept ethnic passions in check eroded, the seeds of nationalism were sown. Gellner points to the Enlightenment as one of the agents preparing the way. In place of the castes that defined social existence in the agrarian age, the Enlightenment offered up the brotherhood of man, a pallid abstraction without the power to compel men's minds and organize society. By the early nineteenth century -- even as statesmen were carving up the map of post-Napoleonic Europe at the Congress of Vienna, oblivious to any ethnic or nationalist considerations -- the snake of nationalism was loose in the garden.

The "cold, bloodless rationalism" of the Enlightenment, Gellner writes, seemed to many nineteenth-century Europeans a repudiation of "warmth and feeling." It was perhaps inevitable, then, that an alternative would spring up, as indeed happened with the emergence of Romanticism. First advanced by literary figures who bridled at the intrusion of rationality into such intimate and subjective areas as love and beauty (Gellner cites Immanuel Kant's definition of love as "benevolence for duty's sake"), the Romantic movement quickly "extended the sphere of its influence from the personal to the political."

What has this to do with nationalism? Gellner points out that the Romantics "valued and praised feeling and specificity -- above all cultural specificity. " He continues, "Where reason is universal in its prescriptions, emotions are linked to specific communities, to 'cultures,' which are, precisely, associations engendered and sustained by shared sentiment, shared by members, and not shared by non-members?" From there, with the aid of philosophers like Herder and later, Nietzsche, the leap to full-blown nationalism is not as far as one might think. For it is in this movement from the defense of cultural specificity to a more assertive cultural differentiation, according to Gellner, that we can see nations being created -- not out of thin air, but with enough deliberateness to cast doubt on the primordialist position.

Despite the rapid rise of nationalist thought in the nineteenth century, nationalism hardly altered the European map drawn at Vienna. "On the whole," Gellner writes, "the handiwork of the peacemakers at Vienna had worn well." Even so, nationalism's dominance in ideology and in literature would more than compensate for its relative ineffectiveness on the ground. "Come 1918," writes Gellner, "the crucial standing of nationalism as a principle of political legitimacy is as self-evident as it had been irrelevant in 1815." So it was that the snake in the garden at Vienna became Versailles's eight- hundred-pound gorilla -- the vaunted principle of self-determination, which the conferees would honor to such drastic effect.

These ideas did not wash over Europe in a single, even wave of nationalist sentiment. Gellner identifies four contiguous zones in which historical, cultural, and organizational factors combined to produce distinctive marriages between state and culture.

In the first zone, comprising Europe's Atlantic coast, state and culture developed in tandem and were both well established in nation states like England, France, Portugal, and Spain before nationalism came along. Thus, nationalism's effects in this zone were relatively mild. In the second zone, roughly the area of the old Holy Roman Empire, there were two cultures, the German and the Italian, but no states with which to pair them. Nationalism's challenge here, according to Gellner, was to forge states to house the cultures -- a task of political unification that, thanks to the absence of large ethnic minorities and the relative compactness of the territories, was accomplished fairly easily.

It is in the third and fourth zones that matters become genuinely complicated. In the third, Eastern Europe excluding the former Soviet Union, there is a multiplicity of cultures and of states, few of which coincide. When you add myriad linguistic differences to the mix, according to Gellner, this region seems predestined for disaster under the impact of nationalism. The fourth zone, the former Soviet Union, is a work in progress. The imposition of the Soviet empire after the dissolution of its Tsarist predecessor delayed the arrival of nationalism. It remains to be seen what shape nationalism will take in this part of Europe.

Gellner's study of nationalism, far broader and more nuanced than a brief review can convey, is an impressive accomplishment, drawing on philosophy, political science, history, theology, and literature. Indeed, the book's brevity belies its intellectual heft. Perhaps the most valuable lines come in the concluding chapter, entitled "Practical Implications." "Political stability is in itself a good," Gellner writes. "The idea that any ongoing, established political order deserves to be corrected, or even abolished, because it fails to satisfy an abstract principle (such as the 'self- determination of nations') is indeed absurd." Gellner reveals here his acute awareness that, at bottom, the attempt to come to terms with nationalism -- whether it be part of man's primordial past, or the relatively recent creation of ideologues -- is a struggle to master what Isaiah Berlin (citing Kant) called "the crooked timber of humanity," from which, Kant reminds us, " no straight thing was ever made."

Kevin Driscoll is assistant book editor of the Washington Times.