The opening of Tate Modern this Friday poses a difficult but pertinent question: how do we define what it is to be modern? While we may think we can identify literary Modernism in Joyce's stream of consciousness style or Modernist atonality in Schoenberg's music, Modernism in art encompasses a broad spectrum of work, from a Cubist collage to a "living sculpture" by Gilbert & George.
The confusion that still exists about what's modern about modern art stems partly from the blurring of the term Modernism with its cognates, modernity and modernisation. Modernity, to give an example, is the condition you're in if you have an illicit encounter with a total stranger on a plane. Modernisation gives you the aeroplane, the bigger seats, the zip-up fly and the Wonderbra. Modernism, in its turn, suggests that the contemporary condition is the ideal state in which to make art. For this reason the art historian TJ Clark dates the start Modernism as far back as Jacques Louis David's Death of Marat, a painting which was made as a piece of French Revolutionary propaganda in 1793. Marat is Modernist, argues Clark, because it was an unprecedented image made in an unprecedented situation.
The innate radicalism of Modernism is the reason why a true Modernist artist will never get to run an art museum. If the Italian Futurist Filippo Marinetti, who in 1909 said "turn aside the canals and flood the museums", was alive today and director of Tate Modern, we would be treated to the sight of the collection bobbing up and down on the Thames. Today, no one would give an artist that kind of power over a national art collection.
This hasn't always been the case; before Modernism, when artists saw themselves as the keepers of history and tradition, they were all faithful curators of the past. In 1768, the painter Joshua Reynolds was made President of the Royal Academy. Sir Joshua was no Modernist; he saw the establishment of a British school of history painters as entirely dependent on a tradition established by Michelangelo, Raphael and the Antique. The RA impresario Norman Rosenthal has recently claimed that Reynolds was a defender of contemporary art. But Reynolds was only "contemporary" in the sense that he made art continue by continuing to make things that looked like old art.
Almost anyone, given sufficient application and a teacher, can learn to do a decent life-drawing. But the true logicians of Modernism are few and far between, because to win the game of modern art you have to make your own rules.
As the country drags itself from the mire of its own history, the erudite nuances of "Post-Modernism" make little sense, and few of the YBA generation would be happy with that label. The most interesting art that has been produced in Britain over the last decade is resolutely Modernist. Artworks such as Douglas Gordon's film 24 Hour Psycho, Steve McQueen's Turner Prize-winning Deadpan, or Gavin Turk's blue plaque Cave, have the essential credentials of being unprecedented and so clearly of their time. All three are works that have emerged from modernity's dark heart.
But has Tate Modern got its criteria right? Pay a visit and decide for yourself.