A classic is classic not because it conforms to certain structural rules, or fits certain definitions (of which its author had quite probably never heard). It is classic because of a certain eternal and irrepressible freshness.
For what are the classics but the noblest thoughts of man? They are the only oracles which are not decayed, and there are such answers to the most modern inquiry in them as Delphi and Dodona never gave. We might as well omit to study Nature because she is old.
The fact is, the public make use of the classics of a country as a means of checking the progress of Art. They degrade the classics into authorities. They use them as bludgeons for preventing the free expression of Beauty in new forms.
Books that have become classics -- books that have had their day and now get more praise than perusal -- always remind me of retired colonels and majors and captains who, having reached the age limit, find themselves retired on half pay.