How does Biff ‘s realization that his life is a lie underline the theme of the play?
One of the major themes of this play is the difference between appearance and reality. The members of the Loman family have been scurrying to keep up the appearances of a well-adjusted and successful family when the truth is that Willy is no longer successful at his job, and Linda defends her husband and enables him to the point that she could allow him to kill himself. Willy has lived an unfocused and unproductive life, haunted by the realization that his father was an adulterer while Happy hops from one woman to the next in his attempt to find the love and attention he didn't get from his parents.
Everyone attempts to keep up this appearance with horrific results. Willy is finally pushed to the point of suicide. At the grave, the absence of doting mourners is obvious, and Biff is finally driven to the epiphany, "We never told the truth for ten minutes in this house" (Requiem). His avoidance of finding his father with another woman is finally released. He understands his own drive to work on the land instead of in the business world and sets off to find it. Unfortunately, his mother and brother remain in the same state of mind, hopefully NOT doomed to repeat Willy's fate.