Now Biff and Happy Loman enter the scene. They are Linda and Willy's two sons. Biff and Happy get along well, but they're still living at home even though they're at the age that they should be out in the world seeking their respective fortunes. Biff says he is 34 years old so maybe Happy is 30 or 31.
           At this time, Willy and Linda have been talking in the kitchen, but once Linda goes to bed, Willy keeps talking. He has a long imaginary conversation with Biff and Happy as children. He's shows signs of Schizophrenia and maybe manic depression. I think he loves his sons and he's proud of them, but wants them to get out of the house and start a life of their own. 
     This addition to Willy's character makes me think. What caused him to develop some psychological disorder? Was it inherited? Or did some event traumatic event in his  life cause this? Perhaps it was the long hours of solidarity while driving from state to state. Or maybe the recurring disappointment of not making a sale. Will we find out? Or is it simply a detail that doesn't pertain to the plot?