'If I was a writer, and dead," wrote Roland Barthes, "I would like my life to be reduced, thanks to the care of a friendly biographer, to a few details, a few tastes, a few inflections - let's call them biographemes."  He should be so lucky. Now Barthes is both a writer and dead, two undeniably friendly biographers, Marianne Alphant and Nathalie Léger, have taken the details, tastes, inflections, paintings, writings, lectures and photographs from Barthes's hitherto impeccably reticent life and made a vast, noisy, interactive, multi-media, many-ringed circus of an exhibition of them at the Pompidou Centre in Paris.  They even find space on the walls to print the above quotation, which shows a nice sense of irony. Barthes, had he been alive today (and not run over by a laundry truck in Paris in 1980, aged 64), would surely have curated the exhibition rather differently, if at all.  As soon as you enter the exhibition, you are confronted by a pristine black 1957 Citroën 19 in all its semiotic pomp. How they got it to the centre's sixth floor is a question no amount of top French penseurs could help you with. It was just this car that Barthes hymned in his contemporaneous essay "The New Citroën". "I think that cars today," he wrote, "are almost the exact equivalent of the great Gothic cathedrals: I mean the supreme creation of the era, conceived with passion by unknown artists, and consumed in image if not in usage by a whole population which appropriates them as a purely magical object."  This essay was typical of Barthes's still massively influential book Mythologies, in which the great critic took everyday things and theorised about them as systems of signs. There were essays about wrestling, the semiotically dense nature of washing powders (and their attendant cult of foam), the ubiquity of plastic, the iconography of Abbé Pierre, the perplexingly desexualised nature of stripping, and more.  Appropriately, in the exhibition, surrounding the Citroën, is a display of plastic things: a 1950s film of sprightly and spiteful French wrestlers, washing-powder ads ("Ah, cette blancheur... Persil!" says one woman dressed in grey to a smug woman in pristine white), a column of Guide Bleu tourist books - each with an apposite Barthesian quote.  Barthes took these objects, which he called signifieds, and said that they had meanings beyond themselves. As a result, they formed networks of signs whose rules he laid bare. Much of Barthes's insight was into bourgeois society's secret codes and his first achievement as a globally significant intellectual was to demystify them and expose their hidden ideological structures. Inevitably, given that Barthes was an aesthete of Proustian sensitivity, this enterprise wasn't as cheerless as it might sound.  Arguably, it took a marginal figure to do what Barthes did, to (in Dennis Potter's words) tear away the masks through which "western society sustains, sells, identifies and yet obscures itself by painting or powdering over its raddled, whore-like visage". Indeed, the history of postwar French intellectual life was of figures from the margins sweeping into the mainstream of Gallic culture and shaking it out of its morosité. There was Julia Kristeva, the Bulgarian Hegelian; Michel Foucault, the homosexual post-Nietzschean gay scientist; Jacques Derrida, the Algerian Jew expelled from school because of his background.  Barthes's theorising, his joy at dallying in the literary margins (such as his analysis of Balzac's Sarrasine), grew from his experiences of being an outsider. Barthes was brought up a Protestant in a Catholic country, a gay man with a lifelong beef against the French bourgeoisie. That beef arguably came from observing how his mother received no support after the death of her naval-officer husband in 1916. She was betrayed by her class, and her loyal son betrayed that class by exposing the grubbily ideological structures behind its most apparently natural and blameless products.  All these Barthesian signifieds are on show at the Pompidou. Together they become one vast sign system whose significance is to make the critic into a lovable saint who had his finger on the pulse of virtually everything that was culturally significant. There are extracts from films about which Barthes wrote, a circular white room floored with white shingle and lined with Japanese artefacts to provide a reflective homage to Barthes's book The Empire of Signs, a chamber of pornographic drawings to commemorate his book Sade, Fourier, Loyola, a glass case with beautiful illustrated editions of d'Alembert and Diderot's Encyclopédie.  Elsewhere in the exhibition, you can listen to Claude Lévi-Strauss helpfully define structuralism, and hear Chico and Groucho Marx in A Night at the Opera. Then it's over to a cleverly designed interactive computer fashion game that illustrates Barthes's analysis of the extensive sign system of the fashion industry.  It's a cute, if somewhat precious show, which serves to take that signified, Roland Barthes, and give him a mythic makeover. Barthes, were he alive today, might not like this, or might experience the not entirely unpleasant frisson of adoring fans canonising him inside a temple of modern art. His lovely voice resounds from speakers in the ceiling, we hear the clatter of his typing (though not, sadly, this reportedly accomplished pianist playing Beethoven), and everywhere there are yellow newspaper cuttings, books and manuscripts.  Alphant and Léger have created a secular icon, a parallel to that priestly legend Abbé Pierre whose status Barthes analysed in Mythologies nearly half a century ago. There Barthes wrote that the myth of the abbé had at its disposal a precious asset: his physiognomy, with its benign expression, Franciscan haircut and missionary's beard. Barthes's physiognomy is just as suggestive and is put to work for myth-making purposes here. There are walls of photographs of Barthes - often close-ups - and their cumulative impact is to create a new iconography of the intellectual. Only in France.  But, there's more to the Pompidou's myth of Barthes than his physiognomy. The most suggestive exhibit in the show consists of a wall covered with hundreds of his index cards. One resists the temptation to genuflect and pray. It is a monument to the might of the intellectual, as is the reconstruction of his study with its books, manuscripts and files - every last scrap might be significant, and every cough and spit might mutate into a holy relic.  The myth of Barthes is never more potent than before this wall, where the faithful bow humbly and look for meaning in his scribbled notes to himself. Only in France could there be such a homage to an intellectual; but by the same token only in France would such an exhibition be curated with such gusto.  In Britain, we don't have the raw material of a multi-disciplinary, aesthetically refined intellectual life to stage thus, say in Tate Modern, still less the temperament to revere a great writer so. True, there was a little Wittgenstein exhibition at the Royal Academy a few years ago, but it was tucked away in the library. We, at least, can be trusted to put a thinker's biographemes where the sun don't shine. Barthes would have probably liked that even less than this show.  · At the Pompidou Centre, Paris, until March 10. Details: 00 33 1 44 78 12 33
He saw cathedrals in Citroëns and modern myths in washing powder. Now a new exhibition turns Roland Barthes into an icon