Full Idea
The avant-garde art of the twentieth century played a significant role in defeating definitions that had prevailed in earlier times, such as ones maintaining that art is representation, expression or significant form
Gist of Idea
Defining art as representation or expression or form were all undermined by the avant-garde
Source
Stephen Davies (The Philosophy of Art (2nd ed) [2016], 2.2)
Book Reference
Davies,Stephen: 'The Philosophy of Art (2nd ed)' [Wiley Blackwell 2016], p.27
A Reaction
I really think the first rule of philosophical aesthetics is 'ignore Marcel Duchamp'. We wouldn't give up our idea of philosophy if someone managed to publish a long string of expletives in a philosophy journal. Would we??