Guénon's argument was that the 20th-century West represented the final stage of a final age, the apotheosis of worldly decadence, in which materialism was emphasized over the spirit, individuality over community. The Renaissance, he proposes, was not a rebirth but a death; science, rationality and humanism were products of delusion. A cure -- or at any rate, a refuge -- could be found in the primordial truths that underlay all religions before modernity's distortions. Guénon scorned democracy; he believed in a hierarchical religious elite and saw himself as one of its elect.

He was right about one thing: there was something revolutionary about the notion of the individual that developed after the Renaissance. He was right, too, that religious and aesthetic compromises were required in a democratic culture with its beliefs in rights and liberties. But he could not imagine any way for a democratic culture of religion to develop: his religious truth left no room for reason or autonomy. The Reformation, for him, was a deformation. These views are what traditionalism shares with varieties of Islamic fundamentalism.

They are also what led it to flirt with various leadership cults and, ultimately, with Fascism, most obviously in the work of an Italian traditionalist, Julius Evola (1898-1974), who was inspired by Guénon. Evola wrote about the Holy Grail, about esoteric belief and magic, but in the 1920's and 30's he tried to influence both Italian Fascism and German Nazism. Mr. Sedgwick suggests that Evola even visited SS headquarters in Germany, urging the organization to supplement its vision with his.

Evola wanted Fascism to be ''more radical'' and Nazism to be less bourgeois. In his 1934 book, ''Revolt Against the Modern World,'' Evola wrote: ''What is really needed is a total catharsis and a radical 'housecleaning.' '' One method was to spur on ''the most destructive processes of the modern era.'' It was a message hailed by right-wing Italian terrorist groups in the 1960's and, in different ways, by the left-wing terrorists who followed.

In a less blunt way, such tendencies were even evident in the early work of the Romanian scholar of religion, Mircea Eliade, who was influenced by both Evola and Guénon in the 1920's and 30's. He later developed what Mr. Sedgwick calls a ''soft traditionalism,'' devoting his career to studying archaic religions and their views, an interest that influenced the course of academic religious studies in the United States. But in his earlier traditionalist days, when he hailed ''a nationalist Romania, frenzied and chauvinistic,'' Eliade was lured by the attractions of Romanian Fascism and the Iron Guards, a past that came to light only after his death in 1986, leaving an indelible blot on his reputation.

This doesn't mean that all traditionalist belief is fascistic or that its restless quest for lost religious truth is inherently problematic; indeed, much of value has come out of traditionalist examinations of art and religion. But its anti-modern and anti-democratic polemics can have disturbing consequences. And Mr. Sedgwick shows that inscribed in its origins is the belief that truth could only be attained by overturning the modern world and its Western host; moral considerations and human consequences are treated as irrelevant.

Traditionalism declared a war in which modernity itself was the enemy. Only in the total destruction of democratic individualism and liberal humanism could the lost wisdom be restored. In some arenas, that is the battle still being fought.

Correction: July 14, 2004, Wednesday An article and a picture caption in Arts & Ideas on Saturday about a group of 20th-century European intellectuals whose movement has been called traditionalism misspelled the given name of one of them. He was Frithjof Schuon, not Firthjof.