Esper

An esper (能力者) is an individual who emits AIM. The term is also used to refer to those enrolled in the Academy City Power Curriculum Program​, as well as magicians by those unaware of the magical nature of their abilities, and therefore define them as 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 individuals with "talent"; this likely refers to Gemstone and each cannot use magic without injuring themselves. AIM is emitted by every esper and their power relates to the properties of their AIM. A Pyrokinetic for example will emit AIM that will heat up their environment. Furthermore, espers have a Personal Reality, which is the basis of their abilities and their capacity to substitute reality with their own. It is in contrast with magic's Idol Theory.

Espers can only access one specific power; Misaka Mikoto, for example, can only control electromagnetic phenomena. Despite this, however, researchers have attempted to create espers with multiple powers, such as Dual-Skill and 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. Active abilities require conscious effort to use, while passive abilities require subconscious effort. Abilities can be classed as both active and passive, such as Accelerator's ability. ​

Their interference with and subsequent distortion of reality to create effects is based on quantum theory. Their interference is an isolated phenomenon, 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 the laws of the whole world is used to make effects.

It is impossible to become an esper once an adult, to the point that the existence of adult espers is seen as improbable.

Academy City's espers have existed for over half a century in the world of Toaru, with the first modern esper being a girl nicknamed "the Beginning Child", who was trained by Academy City based on Meiji-era psychic 's data. The system used for the Beginning Child would become the foundation for the Power Curriculum Program to create espers.

Power Curriculum Program
A person enrolled in this program is called an esper and, through a series of drugs usages and experiments, will be cut off from regular reality and enabled the capacity to substitute it with their own. Espers are ranked according to their System Scan results; it is stated that Level 0 espers barely have enough influence to pass the curriculum's grading exams.

Any individual can use the curriculum to acquire powers, such as Misaka Mikoto, who started out as a Level 1 and worked hard during her training to become the 3rd ranked Level 5 esper in Academy City. There are exceptions of course, as with the case of Level 0s. Furthermore, with the Parameter List, it is apparent that esper potential is limited by various factors. This has resulted in researchers determining that it would be wise to focus on developing an esper whose ability is worth more to the city and whose training is predicted to be more 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 is classified.

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 must meet to officially name their own esper ability, though its uniqueness may be a factor.

Currently, only Academy City can create 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.

Many Academy City students are aware of Gemstone rumors, but treat them as urban legends. This is due to many feeling that it is unfair for esper powers to be gained without having gone through the Power Curriculum Program to attain them. Currently, Sogiita Gunha, who is the strongest Gemstone, and Himegami Aisa are the only two known Gemstone's in Academy City. Kamijou Touma, as mentioned by Kumokawa Seria, does not classify as a Gemstone esper as due to his powers being unrelated to AIM; it is believed that Imagine Breaker is beyond the current understanding of Academy City researchers.