A century ago Marcel Duchamp signed a urinal with the name ‘R. Mutt’, entitled it ‘La Fontaine’, and exhibited it as a work of art. […] There is a useful comparison to be made here with jokes. It is as hard to circumscribe the class of jokes as it is the class of artworks. Anything is a joke if somebody says so. A joke is an artefact made to be laughed at. It may fail to perform its function, in which case it is a joke that ‘falls ﬂat’. Or it may perform its function, but offensively, in which case it is a joke ‘in bad taste’. But none of this implies that the category of jokes is arbitrary, or that there is no such thing as a distinction between good jokes and bad. Nor does it in any way suggest that there is no place for the criticism of jokes, or for the kind of moral education that has an appropriate sense of humour as its goal. Indeed, the ﬁrst thing you might learn, in considering jokes, is that Marcel Duchamp’s urinal was one—quite a good one ﬁrst time round, corny by the time of Andy Warhol’s Brillo boxes and downright stupid today.
– Roger Scruton, Beauty (2009)