The democratisation of cultural criticism over the past 50 years - a product of both the anti-authoritarianism of the late 1960s and the self-interested entrepreneurial spirit of the 1980s - has had two striking consequences: an explosion of popular criticism and a corresponding contraction of evaluative criticism in the academy. In the wider culture, it seems, one opinion is as good as another, and reader reviews on Amazon have as much clout as the Times Literary Supplement. Academics, meanwhile, have retreated into defensive hyper-specialisation: attend an academic conference these days and it is unlikely that you will hear any discussion of aesthetic value or merit.
Somewhere in the middle sits the figure of the "public" critic - who occupies a precarious position, if the frequent cry that the "critic is dead" is anything to go by. One such critic is Michael Billington, who turns 70 this year. He offers a sobering assessment of the predicament of being what he calls a "senior critic".
“It's very complicated. I'm not one of those people who looks back endlessly and nostalgically, but criticism did have a place in journalism when I first started that it doesn't occupy today. It had a solitary eminence. It was a pre-listings age - pre-'puffery'. Newspapers were only eight or 12 pages. There wasn't the profusion of comment or endless series of preliminary interviews we have today."
In the late 1950s and early 1960s, the period during which Billington began to forge his own style while a student at Oxford, popular criticism flourished under the towering twin influence of Kenneth Tynan and Harold Hobson. "They were the two dominant figures," he says. "People would grab the Sunday papers with an enthusiasm, and instantly turn to these columns."
The reason Tynan and Hobson dazzled readers was simple - good writing. "Tynan wrote beautifully. This is the bottom line of criticism, which never gets discussed. I don't mind if I disagree with a critic, or if it's inflammatory, as long as they can write," he says. "To write with maximum volatility and make the arts sound exciting is the responsibility."
In the blogosphere, where comment is free and promiscuous, you would be hard-pushed to identify a critical voice as resonant or as powerful as Tynan's. Even though many bemoan the loss of such prominent arbiters of public taste - Rónán McDonald's book The Death of the Critic is one recent elegy - Billington refuses to take a polarised view. "I welcome the democratic freedom for people to express their opinions, but it's not as new as we think. Before the blogosphere, people wrote letters. I rather miss them. Readers have always reacted, but the game is different now - it's instant and takes less effort."
And in the face of sophisticated publicity machines that attempt to dictate criticism's agenda, Billington believes the public craving for distinctive, analytical voices is actually stronger than ever. "I'm not going to use the word expert - but there remains a definite hunger for someone who has more experience of a particular art form. People may dislike authority, but however much they regard critics as inadequate and parasitic, they still like an opinion to bounce off."
For Billington, the role of the critic is a political one. It is his unwavering conviction that the critic's duty is to be "a one-person resistance movement". "Criticism has become part of consumer culture, hence star ratings are ubiquitous. The critic is one of the last bastions of independent comment in a publicity-saturated age - this rather solitary voice saying, 'Well, hold on, the emperor has no clothes.' We're the little boy."
Billington's championing of Harold Pinter long ago marked him out as a campaigning kind of critic. He has always maintained that theatre should be politically provocative, a stance articulated at length in his history of British theatre, State of the Nation. And the critic, in his view, is a creative accomplice in this - he cites Oscar Wilde's essay "The Critic as Artist" in his support.
Recently, Billington was involved in a heated email exchange with the journalist James Inverne, after Billington reviewed Caryl Churchill's play Seven Jewish Children, about the bombings in Gaza. Inverne criticised his use of the phrase “indiscriminate slaughter", believing it too political. Billington shrugs his shoulders: "I don't see how you can avoid expressing your political opinion in reviewing. If the work of art is addressing something you believe to be an injustice, how can you not address it?"
But didn't Thatcherism fundamentally undermine the language and vocation of criticism by shifting the critical hierarchy itself, valuing spectacle and "bums on seats" above all else, and encouraging reviewers to adopt a boo/hurrah shorthand? Billington isn't sure. "Thatcher did profoundly alter the critical hierarchy for the worse, but I certainly hope I never let those values affect my judgement."
A defiant and effervescent theatre, he argues, is as dependent upon vigorous criticism as the critic is upon the theatre. "Don't forget, first-night audiences of Waiting for Godot walked out, but the critics stayed." Harold Hobson recognised the significance of Beckett's work and saved what is now regarded as the definitive play of the 20th century. So it is no surprise that the angrier letters Billington receives are usually from artists he has not reviewed: "They feel their work has fallen into a void - they want a response."
But, for all that, Billington does acknowledge that his profession is changing. Specialisation continues to be eroded. The National Theatre's live broadcast in June of Racine's Phèdre, directed by Nicholas Hytner, was "a revolution", he says, not only in abolishing elitism, but as an indication that artistic mediums are commingling in a way that will produce a new kind of critic. "The National was anxious film critics didn't review it, but as a piece of cinema it was beautifully composed. Art forms are colliding. Criticism will respond."
Hytner's attack on "dead white male" critics some years ago was an early warning of this shift. The director later apologised for the phrase, but upheld his condemnation.
“What he explained," Billington says, "is that critics like me, though not just me, are in danger of overspecialisation, that we don't see a wide enough variety of art forms." A fair point, he acknowledges, but not one he believes reflects the scope of his own artistic interests. That, surely,
is the paradox of being a "senior critic": having more to say than ever, in a culture that doesn't necessarily want to hear it.
Will Billington be going to Edinburgh this month? "No, I'm having a break from it." Other pleasures beckon. "I'm a cricket nut, so I'm hoping to spend a day or two at Lord's." This is no indication, however, of slowing down. The thing about criticism, he explains, is that it's a job that is never finished.
“Whatever your feelings are about theatre, it's never got to the point where you would like it to be. The mission is never complete."
Michael Billington's "State of the Nation: British Theatre Since 1945" is published by Faber & Faber (£25, hardback)