The term is popularly thrown around as an accusation in arguments on social media and I have seen it misused in many circumstances where people were just accusing others of lying but dressed it up in the fancy term of gaslighting.
Gaslighting is derived from a plot point in the Patrick Hamilton play “Gas Light”. Jack Manningham is searching for jewels in an upstairs flat. During his disappearences his wife Bella notices the gas lighting in her own flat dimming. Jack tries to convince her that she is imagining this, knowing that it is he who is causing the dimming by lighing the lamps in the upstairs flat. This is part of a larger pattern of Jack causing Bella to doubt her own experiences, as he attempts to convince her she is going insane.
Effective gaslighting involves a relationship of some kind. It involves one party in the relationship intentionally leveraging their influence to convince the other party they are mistaken in what they have seen, or heard, or experienced.
Sexual abusers will gaslight victims into believing that the abuse never took place, or that it was consensual, or that the victim actually instigated the events.
A business owner engaged in fraud will manipulate staff members who notice irregularities and will attempt to convince them that they have seen 1+1 and arrived at an answer of 3.
The person doing the gaslighting is generally in a position of power in the relationship. The victorian patriarchal husband, the paterfamilias, the wealthy Dowager Aunt, the boss, a teacher, a mentor, a politician, leader or a tribal elder.
Gaslighting is a form of psychological manipulation. It is not a one off event. You can’t be gaslighted in a single interaction. It requires a long term pattern of behaviour.
It is a behaviour prevalent in religious cults where the “glorious leader” through a structured programme of interactions leads acolytes to doubt their entire belief system and replace it with a blind faith in the paradigm of the leader. Gaslighting is preparatory to brainwashing. By gaslighting you have the acolyte doubt their reality, opening them to manipulation. Then you are free to replace their reality with your own – which is the brainwashing piece.
A form of gaslighting is highlighted in the George Orwell novel 1984. History is edited to reflect current reality. A back issue of a newspaper showing the award of a medal to a war hero is replaced to reflect the current reality where the hero has become an enemy of the state. If you seem to remember the individual was some kind of hero, and you go back to check, you will find your memory of the past is flawed.
These days with Deep-Fake technology you will see evidence of people saying and doing things that never happened. But how will you know the truth? What is reality in a post-truth society?