By destroying their trust in themselves, you make them totally dependent on you and essentially design their understanding of what's real.
The goal is to convince a person that they're insane and that none of their memories or beliefs are reliable. Gaslighting is basically 'crazy making.' It's most often used by sociopaths, cult leaders, lawyers, and bad boyfriends. Regardless of your malicious motive, the tool you're looking for is an insidious form of deception known as 'gaslighting.' So, What Is Gaslighting?
Suppose you want someone to believe in you more than they believe in themselves.
Nonetheless, suppose you need to make someone distrust their own memory and perception of reality.
