Fourth wall

The fourth wall is the imaginary "wall" at the front of the stage in a traditional three-walled box set in a proscenium theatre, through which the audience sees the action in the world of the play. The concept is usually attributed to the philosopher, critic and dramatist Denis Diderot. The term itself was used by Molière. The fourth wall illusion is often associated with naturalist theatre of the mid 19th-century, and especially with the innovations of the French director André Antoine.

The restrictions of the fourth wall were challenged in 20th-century theatre. Speaking directly to, otherwise acknowledging or doing something to the audience through this imaginary wall – or, in film and television, through a camera – is known as "breaking the fourth wall". As it is a penetration of a boundary normally set up or assumed by works of fiction, this is considered a metafictional technique. In literature and video games, it occurs when a character acknowledges the reader or player.