I was watching a film where something like this was the twist ending and it got me thinking, "If somebody believes that they're an impostor of themself is there a name for that and if there is then what is it?"
The name of Impostor Syndrome makes it sound like a perfect fit, but it's not. Impostor syndrome is where one doubts their own skills and fears being discovered as a fraud, not where one actually believes themself to be a duplicate replacement of the real person. I tried looking it up, but with how unreliable search engines are these days, I didn't get any results that matched what I was looking for. The first few pages of results were the Capgras Delusion, which is "the belief that a close relative or spouse has been replaced by an identical-looking impostor." There was also the Fregoli Delusion, which is "the belief that people the sufferer meets are actually the same person." and Subjective Doubles, which is the belief that the person has a doppelganger out there with a life of their own.
Is there a name for a delusion where a person believes that they themself are a duplicate/doppelganger/clone/etc. that's replaced the real version, like the Capgras Delusion except regarding oneself rather than a relative?
