Psychological realism delves into the mental states of characters and seeks the underlying causes for their actions, causes rooted in their psychology. The style of the play need not be realistic in the usual sense, and Arthur Miller's Death of a Salesman is such a play. The set and the way the action moves from place to place is not realistic but expressionistic, but the psychological picture created for each character and the way characters interact is real and rooted in mental states, and the connection between the two generations is the key issue.
The character of Biff is a reflection of his father and carries on in his own life the same sorts of failures seen in his father. It is Willy's wife who states that attention must be paid to the life of Willy Loman. She understands him and his problems, and she forgives his shortcomings. She is, after all, the one who has been most wronged by his behavior on the road and by his leaving her to handle the problems at home. In the end, Willy leaves a legacy behind in the form of his sons, and this is a mixed legacy. Happy accepts the American dream, and more specifically Willy's dream of success, while Biff finally rejects it and proves to be strong enough to face reality as his father never could. He has learned a lesson from the life of Willy Loman, and this is a lesson that others could learn as well if they paid closer attention to his life.
Biff seems always to reject Willy's views and to be opposed to the way Willy lives his life, but in truth Biff has an affinity for his father that he is usually denying. These psychological tensions are brought out through the contradictory actions the boy takes toward his father over time. It is also apparent that the failures in his own life can be traced to similar values as espoused by his father. As a young man, Biff has been much closer to Willy and has accepted the values the father passes to the son. Those values are...