Not a week passes without the Daily Mail or the Daily Express bitterly complaining that art has been taken over by anarchists and crackpots.
Empty rooms with flickering neon, piles of bricks, pictures (beautiful pictures as it happens) made with elephant dung, isolated figures half submerged off the Welsh coast - they exercise the middle classes to the point of apoplexy. But what is their art then? What is the artistic culture of the right?
In a word it is tradition - safe landscapes neatly trimmed and fenced off behind Constable's complacent bourgeois farmers, Mr and Mrs Andrews; portraits of aristocrats and their country houses; Pavarotti singing Nessun Dorma without the references to the tyrannies that murder love.
It begins to seem as though art, literature and music are in some way critical by their very nature. There are a million articles and treatises that try to define cultural achievement - beauty, tragedy, the power of the word - in terms of some inherent quality, some arrangement of the paint on the canvas or the words on the page that is a perfect harmony.
But the quality of great art is not technical but social. It challenges or changes the way we see the world. It alludes to what is not yet present, to what might be, to the "ought" as well as the "is". If it produces only complacent confirmation that what is around us is all that there is - then it isn't worthy of the name.
Critical engagement with reality isn't the monopoly of revolutionary artists. It's one of the confusing aspects of discussions of art that so many dedicated socialists ended up producing something called "socialist realism" which was as far from realism as you could get.
A reflection of dogmas and ideologies, it painted happy peasants in a 1930s Russia where the majority of peasants were hungry and landless; it represented the throbbing machinery of industrial progress when the reality was economic crisis.
The irony, of course, is that the great realists - those who understood the conflicts and the contradictions on which social progress rested - were often very far from revolutionary. Balzac's portrayal of how a burgeoning capitalism corrupted friendship and destroyed innocence in Lost Illusions was a searing critique; Dickens's heroes like Pip in Great Expectations live out in their own lives the tensions between justice and greed, love and competition. That the world is not shaped by heroic individuals but by the acts of ordinary people - those who make history - is perfectly expressed at the end George Eliot's Middlemarch:
"[Dorothea's] full nature... spent itself in channels which had no great name on earth. But the effect of her being on those around her was incalculably diffusive. For the growing good of the world is partly dependent on unhistoric acts; and that things are not so ill with you and me as they might have been is half owing to the number who lived faithfully a hidden life..."
For me the key to this passage is the word "faithfully" - for Dorothea's story is partly at least about an attempt to live a life in solidarity and concern for others.
In our society artists are set apart. We have theories to explain why they are what they are, ranging from a special "inspiration" to some extraordinary event in childhood. Whatever the explanation, artists are different from the rest. While the majority of people labour at jobs that deny their creativity and imagination, a privileged few are given the right to make art - whose value is immediately expressed in terms of cash.
All we know about Damien Hirst's diamond-studded skull is how much it is worth, not what it is trying to say about how we see death or diamonds. But that is not just another expression of the way that capitalism as a system turns every human product into commodities. It is also a theft.
It is the impulse of art to explore beyond surfaces, to question appearances, to bend language into unexpected shapes. That's why Pablo Picasso is a great artist - not just because he painted Guernica but because his early Cubist work shattered the naturalistic view of the world and represented reality as full of conflict and contradiction.
Dmitri Shostakovich is a great composer, not because he made the great celebratory Stalingrad Symphony for Joseph Stalin but because he incorporated jazz into his music and created string quartets of extraordinary beauty, full of challenges to the way we hear the world.
Each of us has our own examples. But it is the quality of all great art to be "life affirming", as Leon Trotsky put it: to crack surfaces and challenge complacency and open up the imaginative potential that one day, in a different world, we will each be able to explore for ourselves - and not just those few given permission to exercise their creativity while the rest are denied that possibility.