Postmodernism: Style and Subversion, Victoria & Albert Museum, London

Squaring up to Modernism, its successor was more of a tendency than a movement. But it regained classicism from the dead hand of Fascism

(PAUL MAENZ / ARCHIVIO GIULIO PAOLINI TURIN)

In the 1990s, this newspaper occupied offices in a building by the Argentinian architect, Cesar Pelli.

It wasn't just the height of Pelli's tower that made it monumental. One Canada Square, otherwise straightforwardly flat-sided, was topped off with a pyramid – a form which instantly identified it as an obelisk, albeit of a clunky, non-tapering kind. But for that, Pelli's tower might have been a straightforward piece of Modernism, the sort of thing run up in thousands around the world between 1945 and 1975. By putting one piece of geometry on top of another, though, it killed Modernism off. Canary Wharf, in which Pelli's building stood, was Postmodern, not Modern.

It was a familiar story in just about every field of art-making. Postmodern novels interrupted themselves to question their authors' competence. Postmodern designers reached into the ragbag of kitsch and drew out diamanté and Mickey Mouse ears. DJs mixed tracks, revelling in the power of mismatch. And artists such as Jeff Koons made trademark Postmodern works – glittery things that celebrated the worthlessness of their subjects (balloons, paedophiles, cute little puppies) with impossibly high production values and price tags to match. All this is the subject of a new exhibition at the V&A, a show which, like its subject, is easy to take at face value.

For a style to be called post- anything, lands it with a problem. Defining yourself by rejection sounds adolescent, especially when the thing rejected is as solemn as Modernism. Modernism grew up in a world menaced by fascism. If Hitler, Mussolini and Franco were going in for history – arcades and colonnades, capitals, figure sculpture – then Modernism would reject it. Instead, it looked to rational lines and forms, a geometry that was supranational rather than national, super-ego not id. Oscar Niemeyer's United Nations headquarters in New York, a Modernist icon, is world peace made concrete.

The trouble is that there are only so many games you can play with squares and rectangles, and only so long you can play them. By 1960, the American architect Robert Venturi was already testing the Postmodern water by putting a broken pediment on a house he designed for his mother. When Venturi and his partner, Denise Scott Brown, visited Las Vegas a few years later, the experience "jolted them both clear out of their aesthetic skins". Scott Brown's phrase is significant. One of the characteristics of Modernism had been that it was intrinsic, its moral high-mindedness radiating from the inside out. Postmodernism inverted this rule, or rather everted it. From now on, art and architecture would be all about skins: how things looked, rather than how they were.

As you might expect of the country that gave us bella figura, Italy was an early signatory to the project. The Italian sculptor, Giulio Paolini, once a stalwart of Arte Povera, began making historicist work whose fascination was with the making of historicist work: in L'Altra Figura, two cod-classical plaster busts stare down at the fragments of a third. Ettore Sottsass's Casablanca sideboard for the design group Memphis married the space-invader look of a 1980s video game to a vaguely Japanese aesthetic and covered the lot in pink-and-yellow plastic. Modernism had held that decoration was sinful, that form must follow function. Sottsass cheerily cantilevered the external shelves of his sideboard at such weird angles that they served no function at all.

For all that, Casablanca's Postmodernism is only skin deep. Open the doors and you will find an extraordinarily high degree of finish – beautifully cut tenons, perfect chamfers. It is like looking into an 18th-century cabinet. So, too, with Jeff Koons's Louis XIV, a portrait bust of the Sun King in a generic swagger style. Koons has the Postmodernist's magpie eye for the shiny; the phoniness of his image is enforced by its being made in polished steel. The French historian Jean-Claude Lebensztejn described the Postmodern look as "calm and blank", and Koons's work is this in spades. Its mirrored surface answers narcissism with narcissism. But Louis XIV is also very skilfully and expensively made, using methods more genuinely historical than the image's gimcrack historicism suggests.

What all of this points to is an unexpected moral depth to Postmodernism. Rediscovering ornament was always going to be tricky, especially in architecture: the last time we'd seen the cod-classicism of Ricardo Bofill's dormitory town, Les Espaces d'Abraxas, was in the designs of Albert Speer for Germania. Also, it was not in the nature of a movement whose mood was cheeky rebellion to write its own manifesto: Postmodernism could only ever be a tendency. What emerges at the V&A, though, is the unexpected sense that Postmodernism was underwritten largely by fear. Like any rebellious teenager, it did what it did to see if it could get away with it. Then the world grew up, and moved on.

To 15 Jan

Next Week:

Charles Darwent gets first sight of Firstsite in Colchester

Art Choice

Take a stroll around the Yorkshire Sculpture Park and enjoy Spanish artist Jaume Plensa's large-scale works, which encourage "sensory exploration" (to 22 Jan). At Tate Britain in London, it's all fire and brimstone with John Martin's Apocalypse. Embrace the drama and disaster of the Victorian artist's neglected oeuvre (to 15 Jan).