Discuss how and why the idea of duality is so prevalent in nineteenth century writings, especially in The Importance of Being Ernest by Oscar Wilde.

Duality, or the idea that "man is not truly one, but truly two," as Dr. Jekyll puts it in Stephenson's Dr. Jekyll and Mr. Hyde, is one of the most prevalent themes in fin-de-siecle literature. The idea of man's inherent animalism, merely restrained by the trappings of society, rose out of Darwinian ideas about man's descent from apes. The Victorians were also extremely preoccupied with the concept that "criminality" would have an effect on man's physical appearance and believed that various features would "betray" criminal tendencies. These ideas played into concerns that Victorian society was, at its core, hypocritical: the more rules there were about how to conduct oneself in genteel society, the darker was the hidden underworld in which these seemingly genteel men comported themselves at night.
Victorian London was a hotbed of child prostitution, drunkenness, violent crime, and covert homosexual establishments; in London, too, the everyday poor far outnumbered those in high society circles, and yet they were largely ignored and unrepresented. In The Importance of Being Earnest, there are a number of "in-jokes" assumed to suggest that the secret lives lived by Jack and Algernon have a homosexual connotation. The title itself is a pun: "Earnest" was a word used by homosexual men to describe themselves, while Algernon's friend "Bunbury" had a similar connotation. This is a lighthearted play, but it marked the beginning of Wilde's descent into disgrace—its opening night was disrupted by the father of Wilde's lover—and it reflects the duality of Wilde's own existence at this time. Similar dual existences, with politesse used to cover the true nature of man, can be found in Wilde's The Picture of Dorian Gray, Stoker's Dracula, and Stephen's Jekyll and Hyde, among others. All seem to critique the willful blindness of Victorian high society to its own hypocrisy and to explore the idea that social norms are inherently something from which we want to escape in order to live our true lives.