What is the theme in A Life in the Theatre by David Mamet?

The lines between reality and fantasy are blurred by certain aspects of A Life in the Theatre. For Robert, life is the theater. He plays the role of a professional actor both onstage and off, insisting on indoctrinating John with his accumulated knowledge. Throughout A Life in the Theatre, Robert does not draw many definite boundaries between the fantasy world of the theater and the reality of life offstage. Though he tells John in scene 6 that an actor must have a life outside the theater, in scene 5, Robert goes on about how ugly sounds, like voices and accents, bother him on and offstage.