There is in every person the possibility of an "Integrated Soul Personality". However, normally the average person is split to a greater or lesser degree, dependent upon the amount of pain, trauma and undigested stress in their lives and dependent upon the amount of work they have done to integrate their personalities by means of therapy and meditation.Therapy and psychology allow intellectual appreciation of the problem in ourselves and others. It takes meditation to heal the splits and integrate the separated selves.
In trance states, a Shaman would often deliberately become possessed by the souls of dead ancestors, who would impart advice and wisdom. Again, it takes a strong sense of the Higher Soul Infused Personality to be able to enter into the various unintegrated parts of the personality and then return as it is easy to get lost.
For thousands of years it was common knowledge that Personalities migrated from body to body, lifetime after lifetime. Only a Soul Integrated personality can remember their past lifetimes. It is fairly common for Split patients to have at least one alter who claims to be a dead ancestor and their access to this information shows that these people are in the process of integration, their amnesia is starting to slip.
So called normal people have no access or experience of this reality through deep amnesia and they are fearful of the tales of ghosts and ancestors because of their not wanting to face up to their painful memories which are the real cause of their amnesia.
However, there is no need for this fear. The real experiences we cannot face up to as children, once accessed in energy enhancement meditation are easily and painlessly digested and integrated by the adult.
However, the cure for split personality for everyone is integration of the splits by grounding all the negative energy created by traumatic experiences which sustains the splits. As we ground all the negative energy through meditation, so the splits disappear and one integrated soul personality becomes in charge..