In 2001, a cleaning lady in an art gallery had thrown away an art work by Damien Hirst, consisting of dirty glasses and a full ash tray. In January 2005 garbage collectors threw a heap of litter from the street in their car, which afterwards appeared to be a modern sculpture.
In his book 'Art versus Nonart' (2003) Tsion Avital relates how a museum director told him that in one of the boxes, which had been delivered in preparation of an exhibition of modern art, nothing else but small pieces of polystyrene could be found, the usual filling material to safeguard transportation of art works. Since they could not find any object, assistents cut the polystyrene pieces, thinking the work was possibly packed inside the polystyrene. But no, nothing there. Maybe the work had been stolen or got lost in some way? When the artist was contacted with the news that the boxes had arrived but without the work, it appeared that the pieces of polystyrene were the work of art, upon which the artist took the museum into court for damaging his work.
In Rumania a man had hanged himself in a park with modern sculpture, and only after some considerable time the public began to realize that he was not part of the exhibition. Maybe this story is not really true, but that it circulates is an indication that there is a consensus that everything - really everything - can be art. Which means that it is impossible to distinguish a work of art from anything else.
(Source: 'Niet alles is kunst', Kraaijpoel, Meyer, Allan; Aspekt 2010, unfortunately not as yet in English.)
It all began with the 'fountain', which in reality was and always will be a pissoir, by Marcel Duchamp, a 'readymade' from 1915. Duchamp was a joker, not a serious artist, and the idea that a 'readymade' could be art opened the door to the immense sea of nonsense which began its crazy trajectory through 20C art history.
Duchamp: 'Fountain', 1915
In music, it was Eric Satie who turned his limitations into an asset and wrote some interesting works, some of them really beautiful (Gymnopedies), and one remarkable work: 'Socrate', a very subdued cantata where absence creates the dreamy atmosphere of an empty room filled with nostalgia. But it was especially his nonsense pieces which were taken-up with delight by postwar nontalents like John Cage, seeing in Satie a legitimization of their lack of musical imagination, skill, and their 'rebellion' against a musical culture where they would never be accepted as serious musicians.
A link to 'Socrate':
With the liberation from any sense of aesthetics, artistic meaning/achievement, and skills, concept art and concept music is the bottom line of decadence, and not even skillful decadence as we sometimes can admire in fin-de-siècle art and music, but cheap, kitschy, puerile decadence, the climate of the playing ground, where people fool around and exploit the gullable for money. Probably the man in the sculpture park was a concept artist who finally understood the non-meaning of his trade.