Quick, give an example of the ideal of beauty in the 20th century. Did you name a Mondrian painting, or Marilyn Monroe? There’s a good chance it was the latter (or some other movie star,) but what will art historians centuries from now have to say on the subject? “Art is no longer interested in providing an image of natural beauty, nor does it aim to procure the pleasure ensuing from the contemplation of harmonious forms,” and that’s fine for the avant-garde, but the divergence of art from the concept of physical beauty does mean that it is difficult to predict which aesthetic tradition will have real staying power.