Tragedies are works which focus upon human suffering (both mental and physical) and bring about a catharsis (release of strong, sometimes repressed, feelings and emotions) in an audience. Through his many plays, Arthur Miller illustrates his role as a theorist of tragedy.
A theorist of tragedy examines the abstract principles of the tragedy. Aristotle, in Poetics, defines the characteristics of the tragedy. These characteristics are seen in many of Miller's works (The Crucible, Death of a Salesman, and After the Fall). Each of the texts possess characters who bring out fear, worry, and concern in their audience. Readers feel worry and fear for both Elizabeth and John Proctor, concern for Willy Loman and his family, and concern for Quintin's future.
Miller does not "sugar coat" the struggles of people in the world. Instead, his characters are offered up as sacrifices in order to teach Miller's audiences about hysteria, challenges, pain, lies, hardships, and fear. As the characters traverse through their lives, the audience can both relate to and feel for them openly.
In this sense, Miller illustrates his position as a theorist of tragedy. He illustrates his recognition of the importance of the feelings of the audience and the character's influence upon them.