This, as mentioned by @arrgghh is the phenomena that I am most interested in, sympathetic towards, and want to know about, in myself and others. My psychosis was this - the seeming discovery of something very unpleasant inside me.
Rather than reject my psychosis, I have spent the last 30 years or so attempting to explain my psychotic experience in a way this is not ‘crazy,’ hocus pocus or what have you.
There are lots of psychologists and philosophers that claim that there is a duality in the human psyche. This theory is proclaimed by very down to earth, rational theorists such as Adam Smith, George Herbert Mead, Mikhail Bakhtin, and Hermans and Kempen.
I work in a department of economics, so I may be biased, but the economic aspect of these theories, as espoused by Adam Smith seems to me to be the particularly powerful motivation for the situation to continue. Adam Smith argues that it is due to the fact that we split ourselves that we engage in human economic endeavour. If we were not split we would rest when we are physically sated, when we have had sex, eaten, we would rest, as animals do. But if we always see ourselves from the point of view of an other which is in ourselves, then their is no end to our desire. We don’t just want a mode of transport to get to place B more quickly, a bike might do, we want a cool car, even a Rolls Royce or Ferrari. We don’t want just an apple, or some rice, but sushi, and caviar.
Few, if any, of these theorists explain however, how it might be possible that we can be dual or split.
But there are a couple or three theorists at least (Freud, Nishida, Rochat) that suggest (or hint) that we can spit ourselves only because the other role, other than our selves, is scary, very unpleasant, something that we do not want to see because it so horrific, and in that sense “demonic.”
The nastiness-theory-of-human-splitting is not complex, but quite simple, and down to earth.
Children get to know themselves from a first person perspective. They then later learn that they are that which they can see in mirrors and that which can be referred to by pronouns and names. At this point, when introduced e.g. to the little person in the mirror, rather than reject their former first person self, they learn to have a relationship between the two selves.Since infants are accustomed to relationships between parents and infants they initially understand their own internal relationship in this way: that they are a parent-child diad. The problem, and nastiness, may come later when this relationship becomes sexualised. Then every taboo comes to bear.
If you are playing the role of a mummy and a child and start to feel sexually self-attracted then:
This internal relationship if such exists would be incestual, between a parent and child.
This internal relationship if such exists would be intergenerational (between a parent and child) and yet sexual so it would be paedophile.
This internal relationship if such exists would be a homosexual relationship (there is only one person in which it occurs, a person that is necessarily of one sex)
This internal relationship if such exists would be a autoerotic (masturbatory) relationship since again there is only one person there.
Then, in a paradoxical way, the overlap of all these socially condemned, abhorrent relationships, the very unpleasantness of this relationship, facilitates its continuation. If it were not for the unpleasantness, the duality would be outed, out of the closet, and then disintegrate, be unconcealed.
Rochat further argues that getting a whiff of the other in self, can lead to schizophrenia: paranoia, voices, anything is better than seeing the duality that is in us (as Pans said).
But maybe there is a way of accepting, or even being grateful towards, nice to, loving in a non sexual way, and transforming an unpleasant relationship into a pleasant, loving (in a nice way) one.