An excellent essay that is extremely pertinent to this question is Arthur Miller's "Tragedy and the Common Man," in which Miller discusses the traditional classical understanding of tragedy as applying only to royal, high-born characters and argues that tragedy is a genre that is just as applicable to "normal" characters, or the "common man." The classical tragedy does indeed only pick noble-born subjects to demonstrate the catharsis that is such an essential element of tragedy. Miller argues that this is incorrect for two reasons: firstly, modern psychiatry has shown that the complexes that famous tragic heroes such as Oedipus suffered from affect everybody, and secondly, the way that all humans, whether noble-born or not, appreciate and love tragedy, strongly indicates that tragedy is something that applies to all. Miller then goes on to underline what is at the heart of the genre of tragedy:
As a general rule, to which there may be exceptions unknown to me, I think the tragic feeling is evoked in us when we are in the presence of a character who is ready to lay down his life, if need be, to secure one thing--his sense of personal dignity. From Orestes to Hamlet, Medea to Macbeth, the underlying struggles that of the individual attempting to gain his "rightful" position in his society.
This therefore leads him to use this common thread in his own modern tragedies, but through using the "common man" instead of only using such important and noble individuals. Miller goes on to explain that actually taking a common man as a tragic protagonist allows the playwright to explore the ways in which he or she is barred from gaining his "rightful" place in society by big forces within that society that seem to stand against him or her. This helps audiences to understand the struggles of characters like Willy Loman, who are prevented in so many ways from gaining their "rightful" position in society by the forces of consumerism. When considering Arthur Miller as a theorist of tragedy it is important to appreciate therefore the impact he had in forming what has come to be known as the domestic tragedy, which makes tragic heroes out of "common" people.
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.