Artist: Avant-garde artists intend their work to challenge a society's mainstream beliefs and initiate change.
Conclusion
If an avant-garde work becomes popular, it’s an unsuccessful work.
Evidence
Avant-garde artists want to challenge mainstream beliefs and change them. Mainstream beliefs don’t change much over any short period of time. (The idea being that if you’re popular with the mainstream, you must not be challenging and changing the mainstream as you had intended)
Evaluation
The author is rebutting the claim in question. She ultimately argues that if an avant-garde work becomes popular, it is not successful.
Goal
We want something like .