11 ideas that everyone accepts that are wrong.

1. That popular music is the authentic voice of the  people, not the sound of commerce and habit. 
2.  Originality comes only from the untrained. (training in related fields doesn't count)
3. Actors and actresses are the same as the roles they play. It follows that composers are the same as their compositions.
4. Our perceptions of art are not influenced by publicity and advertising. 
5. Our most successful musicians are also our greatest artists. 
6. Our most successful composers are also are best.
7. Only art which is reviewed matters.
8.  A rich gatekeeper can't artificially create and maintain a style.
9. When a new style emerges the old styles die.
10. Only my point of view is correct.
11. Poor scansion is acceptable in opera.