The fourth wall

The fourth wall is the imagined boundary separating performers from spectators in realistic theatre. Performers act as though the audience cannot see or hear them.

Fourth-wall break: A moment when a performer or fictional character acknowledges the audience or the fact of performance. It deliberately crosses the boundary that realistic theatre normally preserves.
Denis Diderot: An eighteenth-century French philosopher, art critic, and writer who developed influential ideas about acting and drama. His advice that actors ignore spectators anticipates the fourth-wall convention.
Epic theatre: Bertolt Brecht's approach to theatre that interrupts dramatic illusion to encourage critical thought about social conditions. It rejects sustained immersion and makes the mechanics of performance visible.
Cinema of attractions: Early cinema that foregrounded spectacle and directly solicited the viewer's attention rather than sustaining narrative absorption. Its direct exhibition contrasts with the invisible-observer position associated with the fourth wall.
Naturalistic acting: An acting style that presents behavior as plausible, spontaneous, and continuous with ordinary life. Its performers sustain the illusion that the audience is absent.
The Paradox of Acting: Denis Diderot's essay arguing that great actors control their performances rather than simply feel the emotions they portray. It describes acting as if a wall separates performers from spectators.
Alienation effect: A theatrical technique that makes familiar events seem strange to prompt critical examination. Brecht used it to prevent spectators from accepting stage action as transparent reality.
Breaking the fourth wall in film: A film technique in which a character acknowledges the camera or addresses the audience. The camera often occupies the position of the stage's imagined fourth wall.
Proscenium: The architectural frame around a stage opening that separates the stage from the auditorium. The stage opening often supplies the literal frame for the imagined boundary.
Realism (theatre): A theatrical movement that sought to represent ordinary life through plausible characters, settings, and behavior. The fourth wall became a defining convention of realistic performance.

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