The Italian artist Piero Manzoni put his excrement into tin cans in the early 1960s and offered it as art, saying that he was exposing "the gullibility of the art-buying public". The revelation that the cans are in fact filled with plaster is fiercely dividing the art world. "Modern art is shit," says Eileen Marley, arch critic of the modern art movement. But modern art collector Jack Warner disagrees. "Modern art is not shit," he counters.