Death of A Salesman: Themes Analysis

Death of A Salesman has several themes that run throughout the play.  The most obvious theme is the idea of reality versus illusion.  Though Linda, Biff and Happy are all unable to separate reality from illusion to some degree, Willy is the main character who suffers from this ailment.  For years, Willy has believed that both he and his boys (particularly Biff) will one day be great successes.  Though he's a disrespected salesman, he calls himself the "New England man." Though Biff has done nothing with his life by the age of thirty-four, Willy tells others and tries to make himself believe that his son is doing big things" out west.  Willy's brother, Ben, continually appears in the troubled man's mind, offering hints on how to make it in the world of business.  Willy feels that he must live up to the standard that Ben has set, but this is found to be impossible by the end of the play.  Only Biff ever realizes who he is ("a dime a dozen") and what his potential really is.  He is the only member of the family to finally escape from the poisonous grasp of illusion. 
One of Miller's secondary themes is the idea of the American Dream.  Throughout his play, Miller seems to criticize this ideal as little more than a capitalist's paradigm.  Though Willy spends all of his adult life working for a sales company, this company releases the salesman when he proves to be unprofitable.  Willy confronts Howard, his boss (and Miller indicts free market society), when he charges, "You can't eat the orange and throw the peel away-a man is not a piece of fruit." Here, Willy feels that Howard has gone back on his father's word by forgetting him in his golden years, throwing away the peel after eating the orange, so to speak.  Thus, Willy is unable to cope with the changing times and the unfeeling business machine that is New York. 
In many ways, Death of A Salesman has a tragic theme consistent with great tragedies such as Oedipus the King and others.  Though Willy is a very modern man, and certainly not a member of the aristocracy, he lives a very tragic life.  Though he believes that he and his sons are great men, his flawed character perverts his idealistic vision of success and happiness. 
The idea that "personality wins the day" is one such flaw in Willy's logic.  Indeed, substance, not personality or being well liked, is what wins the day.  Charley and Bernard, who have success but not personality, prove to Willy that his notion is incorrect.  But unfortunately, Willy never understands this, and so goes to his grave never truly realizing where he went wrong.