Luigi Pirandello's 1921 play Six Characters in Search of an Author is an example of modernism, in which, as in the plays of Brecht and Beckett, the play breaks through the "fourth wall" of the proscenium and impresses upon us its own theatricality, through use of masks and other devices. This rhetorical construction is known as "metatheater," a theater which reflexively comments on the nature of theatric illusion rather than simply presenting an illusion.
Pirandello's audience in this context would immediately have associated the masks with two theatrical traditions, those of classical Greek tragedy and comedy and a native Italian one of Commedia dell'arte.
In classical Greek comedy, in which masks are worn, one standard feature is known as the "parabasis," in which an actor playing the playwright speaks directly to the audience, usually commenting on the nature of the play itself.
Commedia, even more than Greek comedy, uses stock characters named only by type (the old man, the clever servant, etc.) and includes interruptions and interludes, improvisations, and asides to the audience. The masks suggest that the very radicalism of Pirandello's metatheater is in fact grounded in historic traditions, and the masked characters, thus evoke not so much the illusion of individual people but the history and nature of theater and character themselves.