Self-reference

In natural or formal languages, self-reference occurs when a sentence, idea or formula refers to itself.

Self-reference is studied and has applications in mathematics, philosophy, computer programming, second-order cybernetics, and linguistics, as well as in humor.

Contemporary philosophy sometimes employs the same technique to demonstrate that a supposed concept is meaningless or ill-defined.

[2] In mathematics and computability theory, self-reference (also known as impredicativity) is the key concept in proving limitations of many systems.

[3] Numerous programming languages support reflection to some extent with varying degrees of expressiveness.

[4] 'Taming' self-reference from potentially paradoxical concepts into well-behaved recursions has been one of the great successes of computer science, and is now used routinely in, for example, writing compilers using the 'meta-language' ML.

Thinking in terms of self-reference is a pervasive part of programmer culture, with many programs and acronyms named self-referentially as a form of humor, such as GNU ('GNU's not Unix') and PINE ('Pine is not Elm').

Examples include Miguel de Cervantes' Don Quixote, Shakespeare's A Midsummer Night's Dream, The Tempest and Twelfth Night, Denis Diderot's Jacques le fataliste et son maître, Italo Calvino's If on a winter's night a traveler, many stories by Nikolai Gogol, Lost in the Funhouse by John Barth, Luigi Pirandello's Six Characters in Search of an Author, Federico Fellini's 8½ and Bryan Forbes's The L-Shaped Room.

Speculative fiction writer Samuel R. Delany makes use of this in his novels Nova and Dhalgren.

Nova ends mid-sentence, thus lending credence to the curse and the realization that the novelist is the author of the story; likewise, throughout Dhalgren, Delany has a protagonist simply named The Kid (or Kidd, in some sections), whose life and work are mirror images of themselves and of the novel itself.

The short stories of Jorge Luis Borges play with self-reference and related paradoxes in many ways.

During the 1990s and 2000s filmic self-reference was a popular part of the rubber reality movement, notably in Charlie Kaufman's films Being John Malkovich and Adaptation, the latter pushing the concept arguably to its breaking point as it attempts to portray its own creation, in a dramatized version of the Droste effect.

Kurt Gödel claimed to have found such a loophole in the United States Constitution at his citizenship ceremony.

The ancient symbol Ouroboros , a dragon that continually consumes itself, denotes self-reference. [ 1 ]
Drawloom , with drawboy above to control the harnesses, woven as a repeating pattern in an early-1800s piece of Japanese silk. The silk illustrates the means by which it was produced.
graffiti art on a wall stating "SORRY ABOUT YOUR WALL"
A self-referencing work of graffiti apologizing for its own existence
Self-referential graffiti . The painter drawn on a wall erases his own graffiti, and may be erased himself by the next facade cleaner.