At the time of the opening of Tate Modern – London’s temple to contemporary art – a story swept the press. A visitor had reportedly dropped his wallet in a gallery. Realising this, he went back into the room to find a crowd gathered admiringly round the leather rectangle. When he stooped to retrieve his possession, an attendant rebuked him for touching an exhibit. Whether or not it happened, this anecdote fast became the sardonic gospel of the enemies of modern art, filed alongside similar legends of gallery cleaners accidentally chucking out what they assumed to be rubbish on the building floor but were in fact the famous Turner-shortlisted works Garbage or Sweet Paper.

To conservatives all these stories hold the same moral: that once anything can be accepted as creativity it becomes impossible to distinguish between a work of art and lost property or litter.

This week the anti-modernists were offered another sheaf of newspaper cuttings to keep safe in their wallets. David Hensel, a sculptor from Sussex, submitted to the Royal Academy summer exhibition a piece that consisted of a large bronze laughing head mounted on a plinth of slate and kept in place by a support shaped like a bone.

Pleased to have the piece accepted as item 1201 in the catalogue – One Day Closer to Paradise (edition of 9, £3,640 each) – Hensel was dismayed on visiting the show to find that his effort had been decapitated; he was represented in the exhibition by what looked like a dog’s toy on a paving stone. It turned out that the head had become separated from the support during unpacking.

For the artistic reactionaries the Hensel event tops even the wallet story as proof that modernists would believe that a fart was art if a man in a bow tie told them it was. The sculptor David Mach, a selector for the summer show, was even on record praising the “minimalist” qualities of the bone-on-slab display. And as the faces of traditionalists aped the roaring mouth of Hensel’s missing head they were given even more cause to cackle when it turned out that the bronze bonce had not simply been left behind in a storeroom but had gone before the selectors as a separate art-work and been rejected.

As pointed out over at, yet another bone thrown to the anti-modernist dogs is the fact that the plinth with the bit on top is now expected to sell for far more than the original price of the whole combination. For the provisional wing of the watercolourists association this will prove that modern Britart combines artistic indiscrimination with financial idiocy.

I wonder, though, whether the RA’s embarrassment is quite the humiliation of modern art that it appears. The argument that the selection panel has been stupid – and fooled into elevating a mistake into art – rests largely on the fact that they were not seeing what the artist intended. But an artist’s interpretation of his or her own work has only limited validity; it’s outsiders who decide how it goes down. You can write a play and call it a comedy, but if theatregoers don’t laugh there’s no arguing with them.

Or imagine that the last chapter of a crime novel were accidentally omitted in a mix-up at the printers. Readers and critics who admired the ambiguity of the ending – and welcomed the author’s departure from the convention that every loose end must be tied – are not wrong or stupid. They simply responded honestly to what they were shown and expressed a preference for work that was willing to ignore traditions.

In the same way, Mach’s full approval of what turned out to be half a work is perfectly justifiable. The head part of the artwork is fairly familiar, heavily reminiscent of the laughing heads in the work of the great Spanish artist Juan Muñoz. But the vast slate slab supporting its fragment of skeleton has a peculiarity and spookiness that makes it unusual; dismissable as art only by those who believe that good art necessarily requires heavy effort.

The great critic Professor John Carey caused some horror by concluding in his recent book What Good Are the Arts? that “anything can be a work of art. What makes it a work of art is that someone thinks of it as a work of art.”

Our inner aesthete flinches at this brutal reductionism, but the confusion at the RA proves Carey’s point. There is nothing absurd about the idea that Hensel’s sculpture became more appealing and intriguing to some people when half of it got left in a cupboard.

If someone then went on to claim that any permutation of what Hensel has done is superior to Monet or Picasso, there are arguments of depth, originality and technique that could be marshalled against them. But, finally, any view of the whole or the half of his sculpture is, like all artistic judgment, a matter of opinion.