How does Biff's realization that his life is a lie underline the theme of the play? Why does Biff take Bill Oliver's fountain pen? Why can't he tell his father what happened with Bill Oliver? Why does Biff and Happy leave Willy at the restaurant?

Biff takes the pen because it is something biff will never have. The pen in itself is a metaphor for he American dream- a dream that was attained by his father but never fully fulfilled, meaning that people are never really satisfied with what they have, they always want more.

They leave his father at the resturant because they are embarrassed by him.

Biff cannot tell his father because he realizes that he wants more from his life he wants a better life a life that his father struggled all his life for.