Final answer:
The proscenium stage is called the fourth wall because it acts as a metaphorical barrier that separates the audience from the performance, creating an illusion of an enclosed space. Actors 'break the fourth wall' when they address the audience directly, acknowledging their presence and interrupting the illusion.
Step-by-step explanation:
The proscenium stage is often referred to as the "fourth wall" because it acts like a window through which audiences view the performance. This comes from the setup where the stage is framed by a proscenium arch, creating a visible barrier between the actors and the audience. It is this frame that forms the fourth wall, a metaphorical division suggesting there are three other walls encasing the action on stage. These other walls are the backdrop and the wings on either side, which, along with the proscenium, enclose the stage much like a room. When a performer addresses the audience directly, it is said they are "breaking the fourth wall," disrupting the imaginary barrier and acknowledging the presence of the audience. In contrast to stages like the thrust or the arena, the proscenium stage supports this illusion by potentially hiding all technical elements of a production. This structure creates an environment where the audience is a passive observer of the dramatic narrative unfolding before them. Proscenium stages are the most common type of theatrical space, and if you have attended a theatre performance, it was likely in a proscenium theatre where the stage directly faces the audience. The division between the spaces for audiences and the spaces for production is distinctive in these theatres. Familiarity with the proscenium stage helps both the audience and performers maintain the illusion of the staged reality.