Show to what extent and in what ways dramatists use the irrational behaviour of their characters to further the action of the plays

Willy and Biff are both rather irrational to put it mildly. In All My Sons, the entire play revolves around Willy's descent into madness and eventual suicide. The action of the play is furthered by his reactions to the things around him that have made him such an unstable character. He cannot control himself; period. But it is Willy's actions and irrational behvior that move this plot along from one scene to the next.

I recently watched the screen version of this play starring Dustin Hoffman. It was entirely true to Miller's work.