I’ve been watching a bit of Art School, a series on BBC Two on which five celebrities spend ten days at Chelsea School of Art. For me the star is John Humphrys, though being called the star of a reality television show is a backhanded compliment. When he is not jousting with the tutors, Humphrys looks like a bewildered schoolboy.

He desperately wants to learn the “correct” way to make art. The idea that there is a “correct” way can be a bit of a handicap. He is approaching the whole business with the same acute rationalism that he brings to his usual role of inquisitor to politicians.

Rationalism comes more from the left half of our brains. A psychiatrist called Rotenberg said: “The left hemisphere generates a pragmatically convenient but simplified model of reality.” To make art we somehow have to loosen our grip on logic, surf the complexities of life and not worry too much about what is right.

Humphrys belongs to a sizeable group of people who seem to be mystified about what contemporary art is up to and I have some sympathy with them. I understand their hunger to know by what parameters they can judge an artwork. Every time the Turner Prize comes around someone will ask me: “Yeah, but is it really art?” I think what they are really asking is: “Is it good art?”

People who, like Humphrys, perhaps think that contemporary art is the emperor’s new clothes may judge a work purely for its technical skill or traditional realism. Having been embedded in this fundamentalist bohemian sect all my adult life, to me the rules seem more arcane. They want perhaps to be given a clean empirical way of measuring artistic merit, just as teenagers need a brand to reassure themselves that their trainers look good. To them I say that it takes time to feel comfortable with the slippery language of contemporary art, which is different from the received pronunciation used to intone about Old Master paintings.

Over the past hundred years or so a very particular revolutionary sensibility has influenced the value system used in making and appreciating visual art. When I was a skateboarder, the most admired skaters were not necessarily the most skilful but those that skated with the right “gnarly” spirit. What “gnarly” meant had to be learnt through the skating experience.

It feels to me that the art world today also has its own visual dialect, a kind of educated mischievous slang that is learnt from making, looking at and talking about art for a long time and a love of being challenged or surprised. From outside, the art world must seem like a self-regarding mafia, but it relishes an assault on its values. The dynamic of acceptance into the art canon seems to hinge on the moment when the art world sees an artist’s work and says: “Good rebellion, welcome in.”

A problem for me is that since Duchamp a century ago, anything an artist chooses can be art. Now when judging it I have to make sure that I am using the specific criteria that measure quality in an art work. What those criteria are is just as tricky for me as it is for Humphrys and Co. I look at a work now and think: “I like this,” but am I drawn to it because the juicy red bits would look great next to my yellow sofa or because I agree with its political statement or because it is a masterpiece?

Take those art students who made the front pages a few years ago. Using the special grant that they had received for their degree show, they had gone on holiday to Ibiza and for their exhibition had shown holiday photos, videos and souvenirs. This of course confirmed all the worst fears of the press about modern art, and there was outrage.

The very next day the same students made the headlines again when they showed how they had wrong-footed the prejudiced media and had faked the whole thing, taken the photos on the local beach and hadn’t spent any of the money. I thought, “Very funny hoax, art student fellas.” I enjoyed reading about their prank but was I enjoying it as good art? Hmmm.

Being as sharp and media-savvy as advertising copywriters and making me snicker is not enough. The art world seems littered with clever ideas at the moment, some of them sneaked in under dear old Banksy’s coat. Many of them look to me like cool advertising campaigns (and some end up as such). It seems to me that too often tricksy cleverness is masquerading as artistic talent.

My business is about more than good ideas. For me a successful work of art needs to offer me rewards sensual, emotional and intellectual. If Humphrys wants to understand art he needs to hang around it for more than ten days. As the infuriating bumper sticker says: “If you have to ask you wouldn’t understand.”