I think schizophrenia is phenomenally partially caused at a level of complete lack of integration.
Multiple personality may have a hidden link with it but merely tangentially, and not substantially. Or, the opposite, where the content itself is sacrificed.
The reduction (regression) in dissociative disorder has a limit, tangentially limited, (partially) at a level of abstraction( of the cognitive and identifiable level of the personality) This secondary presence of the process, is typified by the borderline of the personality.
Borderline can at times manifest a complete melt down, but it is reactive to outside stimuli, and not stuck in an internal fiasco.
Now to Your question:
“Are you trying to say that a brain in some cases may causes two or more selves which one self cheats another self by creating illusions? There must be an extra self which is aware of what is doing if created illusions are coherent. If that is true then why does one self always cheat another self? How does one self have ability to create illusion? Do you have ability to create illusion? How does one self learn to create illusion? Why never two selves collaborate (instead one always cheat another)?”
Coherence within and without levels of consciousness may determine the real level of objectivity between competing ‘realities’.
It is not as if an illusion is based on a different paradigm of objectivity, it is merely the level of apprehension which determines a cognative cohesion.
Both levels may be understood , or/ and perceived similarly in which case the verbal cues cause pull toward the conscious understanding ( in sight ) whereas the dramatic pre-cognative episode, prevail a more inter -porous lack of borders.
Illusion is learned as a creative tool of re-differentiating content around the tangent (for lack of a better term), by willfully repeating structural variance.
The illusions become defense apparati, where y they attach more significant autonomous pathways, such as described by Wittgenstein as ‘games’ built on resemblance rather then identity.
“How does one develop this sense instead of a collaboration?”
It depends on the will, to power such a system, that effects the power to will such. The latter was called neuroaesthenia, for the primary symptom of lack of power , or, energy.
Power is derived further on in symbolic effect to will, whereas will stays more on the level of affect.
The illusion to falsify defensively becomes more pronounced as the regression continues to repress the cognative sense of difference into less abstract ( bless his soul) , more formal and more linearly contraindicated content.
There is no real nexus between the psychological one and many (similarly, in philosophical universals , there appear no transandentally cognitive object-therefore it has to be presupposed-just like the saying goes, if god did not exist, it would have had to be invented)
“Why never two selves collaborate (instead one always cheat another)?”
This is the most difficult question, that’s why I left it to the last.
Two selves collaborate when there is an opportunity to do so. If one self is not conscious of a relationship to the other, but is aware of the other, then there is a chance of collaboration. But if one is not conscious of it, it uses other methods , such as trickery, not necessarily to invent another persona, but try to reintegrate with a partially affected semblance.
It really is quite a trick, since the deeply felt inductive lack of cohesion, needs a more general mode of objective sense of identifying motives for defensive postures.
Deep defenses are much more difficult to recover with any account of specificity, it is much more of a wild card, and as such, is more prone to suspensions of validity, as far as using presumtion.
Such presumptive tactics try to produce artificially structured rationalizations., wider in scope. This widening presents the additional problem with how consciously will ful, rather then automatic-axiomatic it is.
Philosophers at times are accused of hiding ontic psychologic specificity, as regards will for choice, by covering it with ontological platitudes.
This can be a form if dissection to the problem of power as energy to enable the formation of the will, and is interpreted as a weakness sans sufficient power for integration.
For with insight that is more peripheral then schematic, such tactics are learnable as partial integrative, and as that goes, simulation on lower level mimic becomes available as the last ditch salvigable effort to protect what little is left of the impoverished content.
Others, not so lucky, fall into total basket cases, forever untouchable and absolutely self contained.