“Tawnee says what she does is Art, Sarge. And she wears more clothes than a lot of the women on the walls around here, so why be sniffy about it?” “Yeah, but…” Fred Colon hesitated here. He knew in his heart that spinning upside down around a pole wearing a costume you could floss with definitely was not Art, and being painted lying on a bed wearing nothign but a smile and a small bunch of grapes was good solid Art, but putting your finger on why this was the case was a bit tricky. “No urns,” he said at last. “What urns?” said Nobby. “Nude women are only Art if there’s an urn in it,” said Fred Colon. This sounded a bit weak even to him, so he added: “Or a plinth. Both is best, o’course. It’s a secret sign, see, that they put in to say that it’s Art and okay to look at.” “What about a potted plant?” “That’s okay if it’s in an urn.” – the complexities of art criticism | Terry Pratchett, Thud!