The ghost is ever present in Hamlet's mind and in the audiences' minds... and the play is constantly concerned with what we do about death... what Hamlet does about death, the way the ghost died... the way that Hamlet inflicts death on Polonius... but also contingent deaths like... the death of Ophelia in her madness for example... and I think that the constant preoccupation of the play... with the way that people react to death... is to me the most fundamental reason why it has been... such an influential work of art.