Alter ego

An alter ego (Latin, "the other I") is a second self, which is believed to be distinct from a person's normal or original personality. A person who has an alter ego is said to lead a double life. The term appeared in common usage in the early 19th century when Dissociative identity disorder was first described by psychologists. Cicero was the first to coin the term as part of his philosophical construct in 1st century Rome, but he described it as "a second self, a trusted friend".

A distinct meaning of alter ego can be found in literary analysis, wherein it describes characters in different works who are psychologically similar, or a fictional character whose behavior, speech or thoughts intentionally represent those of the author. It's also used to design the best friend of another character in a story. Similarly, the term alter ego may be applied to the role or persona taken on by an actor or by other types of performers.

The existence of "another self" was first recognized in the 1730s. Anton Mesmer used hypnosis to separate the alter ego. These experiments showed a behavior pattern that was distinct from the personality of the individual when he was in the waking state compared to when he was under hypnosis. Another character had developed in the altered state of consciousness but in the same body.

Alter ego is also used to refer to the different behaviors any person may display in certain situations. Related concepts include avatar, doppelgänger, impersonator, and Dissociative identity disorder (DID).

In literature
The title characters in Robert Louis Stevenson's thriller Strange Case of Dr Jekyll and Mr Hyde represent an exploration of the concept that good and evil exist within one person, constantly at war. Edward Hyde literally represents the doctor's other self, a psychopath who is unrestrained by the conventions of civilized society, and who shares a body with the doctor. The names "Jekyll and Hyde" have since become synonymous with a split personality or an alter ego that becomes capable of overpowering the original self.

In Pre-Crisis comic books, superheroes and their secret identities are often considered alter egos. The archetypal comic book hero, Superman, assumes the identity of the "mild-mannered" newspaper reporter Clark Kent in order to live among the citizens of Metropolis without arousing suspicion. Whereas Clark Kent's true self is Superman (or rather the Kryptonian Kal-El), Batman is a character created by Bruce Wayne in order to disguise himself for the purposes of fighting crime. However, there has been suggestions that Bruce Wayne is the mask that the true self, Batman wears, in the episode "Dreams in Darkness" in Batman: The Animated Series. The Batman comics and movies such as Batman Begins have also explored the theme of the true self (Wayne) becoming lost in or giving himself over to the alter ego, much like the plot of Dr Jekyll and Mr Hyde. Post-Crisis comics flip this idea around for both superheroes. Superman becomes the persona that Clark Kent adopts in order to freely use his gifts to help the world without jeopardizing his friends, family and personal life. Conversely, carefree playboy billionaire Bruce Wayne becomes the alter ego necessary to hide the true persona of the crime-fighting Batman. The Incredible Hulk comic book series further complicates this theme, as Bruce Banner loses control to the Hyde-like Hulk whenever he becomes angry, yet also depends upon the Hulk's super powers in order to combat villains. Also the Batman villain Two-Face seems to split his alter-ego from Harvey Dent, whose personality changes from being judge-like to changing back to his Two-Face persona and being ruthless using his two-faced coin to determine life and death.

Comic book-inspired alter egos can be seen in other forms of popular fiction, including television and movie adaptations of comic books, parodies of this genre, and unrelated fictions such as Star Wars or Angel.