Tate Britain, London, until 31 August
Policing the borders of art is a tricky business. They’re porous, and they’re constantly shifting. What passes as “art” today may no longer pass tomorrow. It’s like nailing jelly to a tree.
This is not a question that torments most of us. But the movers and shakers in the art world are obsessed with it. Either they’ve got millions riding on their favourites or else they’ve erected palaces of high culture around them.