Esper

An Esper (能力者) is an individual who emits AIM. The term is also used to refer to those who are enrolled in the Academy City Power Curriculum Program​, as well as magicians who are unaware of the nature of their magical abilities, and thus describe them as being esper-related.

Terminology
The original Japanese light novels used the term "Ability User", but before the licensing of Toaru Kagaku no Railgun, the majority of the English-speaking fandom substituted it with "esper". Because its use has become widespread, this wiki uses the term "esper".

A queer event related to this is Seven Seas' English translation of the first volume of A Certain Scientific Railgun, which opted to use "psychic", a term that has been used before by the fandom until "esper" became the standard. Because of this, the English fans that were accustomed to the use of "esper" lobbied for "psychic" to be changed, and Seven Seas acquiesced, even referencing the incident later.

The term "esper" does not automatically imply ESP, one of the two classifications of powers in Academy City, as it could also refer to an ability user that does not have extrasensory perception but instead influences objects in their surroundings, referred to as Psychokinesis. Abilities such as Pyrokinesis are considered esper powers despite the user not having extrasensory perception.

Principles
Espers are described by Index as being individuals with "talent"; this most likely refers to Gemstone espers and each is unable to perform magic without injuring their body. AIM is emitted by every esper; its properties are unique and depend on its emitter and their esper power. For example: the AIM emitted by a Pyrokinetic esper will act to heat up their surrounding environment. Furthermore, espers have a Personal Reality; it is the basis of their esper abilities and is their capacity to substitute standard reality with their own. It is in contrast to the Idol Theory of magic.

Espers are allowed only one specific esper power; Misaka Mikoto, for example, is an electromaster esper in control of phenomena associated with electromagnetism. Despite this however, researchers have made attempts to produce espers with multiple powers, such as either Dual-Skill or Multi-Skill espers. Aside from the mental performance of calculations, no elaborative and preparatory rituals are required by an esper to produce effects related to their abilities.

Moreover, esper abilities are compartmentalised into two categories: Active and Passive categories. Applications of active abilities require conscious, voluntary effort, whilst the application of passive abilities require subconscious, involuntary effort. Esper abilities can be classified as being both active and passive, such as Accelerator's reflection ability. ​

Their interference with and subsequent distortion of reality to produce detectable esper-related effects, is based on quantum theory. Their interference and distortions are isolated phenomena, pertaining only to the observations of the world based upon their Personal Reality. This is in stark contrast with holism, where a large interference with and thus distortion of the laws of the world as a whole are used to produce effects in relation to their abilities.

Power Curriculum Program
An individual who enrolls in this program is called an esper; its purpose is to cut the individual from regular reality and through a series of experiments, drug usage and the like, that individual will be able to achieve and substitute standard reality with their own personal reality. Espers are assigned ranks, which is determined based on the results they have achieved during a System Scan. It is stated that the ability of any Level 0 ranked esper has barely enough influence for them to pass the curriculum's grading examinations.

Theoretically speaking, it is possible for any individual to acquire an esper ability by means of their use of the curriculum. Misaka Mikoto for example, started out as a Level 1 esper, and because of the training she received, she was able to become the 3rd ranked Level 5 esper in Academy City. There are exceptions of course, such as the existence of Level 0s. Furthermore, with the Parameter List, it is apparent that the esper potential of an individual is limited by various factors. This has resulted in researchers determining that it would be wise to concentrate more on the esper development of those whose development is predicted to be of more worth to the city, and more time and resource efficient than that of another person's.

Information regarding the students enrolled in the curriculum, such as their abilities, their level and a brief description of them, is available in the Data Banks of Academy City. Furthermore, certain espers, such as Kamijou Touma, have security protocols in place to ensure that the truth of their abilities are protected.

According to Uiharu Kazari, the name of an esper ability, such as Electromaster or Telekinesis, is decided by the school that its owner is enrolled in. Only under specific conditions can the name of an esper ability be decided by its owner, such as the Railgun. It is unknown however, as to what exact conditions an esper requires to reach in order to be able to officially name their own esper ability, though uniqueness of the ability may be a factor in doing so.

Currently, only Academy City is able to produce espers; although others have tried, such as during the Stargate Project.

Gemstones and speculation
A Gemstone esper is an individual who can emit AIM without requiring participation in any power development program. Gemstones are the beings that Index likely referred to as having "talent"; the envy of their abilities from their peers is what led to the creation of magic. There are currently 50 confirmed Gemstones in the world.

In extension to this, it has been speculated that there may be people who have not realized that they have powers, or that their certain propensities or idiosyncrasies, as subtle as good looks or good penmanship, may actually have this power.