Let me say at the outset of this lecture that I am not going to play that ancient game of trying to define the indefinable. Names of literary genres are but tags for works of art which have certain historical relations, but there is no more reason to believe that Hamlet and the Eumenides have a common essence than there is to insist that Louis Capet and Louis Philippe have a common essence, or that the Lever Building in New York and Lincoln's log cabin have a common essence. People have been trying for years to give satisfactory definitions of such terms as “tragedy,” “comedy,” “novel,” even “poetry,” and they have never succeeded. The reason for their failure is clear enough. Words have a history. When they are first used, it is likely that they are unambiguous, but as times goes on, they are applied to more and more different things.