FUNDAMENTALLY THERE are three sources from which the actor may derive the physical actions which give a scene its visible and outward form and which, having been invented, must be motivated by the actor so that they may be performed as though they were involuntary and inevitable: first, the plot; second, the mood and atmosphere of the scene; and third, the character.
The major plot actions are obvious, and they are clearly indicated in the script: Brutus stabs Caesar; Hamlet kills Polonius; Juliet drinks the potion. Such actions the actor must perform of necessity, but it remains for him to choose a manner of performing them which will be appropriate to the character he is playing. In the plays of Ibsen, and of many other playwrights, however, most of the action of the plot is antecedent action -- that is, action which has been performed before the play begins and which is revealed to the audience only through the dialogue. The Greeks avoided all violent action in their plays and contrived to have all the scenes of violence performed off stage, and then revealed to the audience by means of a tableau or a speech delivered by a messenger.
But even in plays in which most of the action either has happened before the play begins or happens off stage, there is a constantly changing relationship between the characters: they fall in love with each other, or they come to hate each other; they learn things about each other, and come to understand each other to a greater or lesser degree; at the highest level of drama they make self-discoveries and learn to know themselves. But through all of this, whatever the plot development, the main purpose of drama is to enable the audience to get to know and understand the characters and their interrelationships.
In the scene between Nora and Mrs. Linden in the first act of A Doll's House, which was used as an exercise for Chapter 9, Nora reveals to Mrs.