The concept of a SourcePerson or OriginalPersonality is one that is found often in the psychological literature but rarely seems to be examined for it's implications. Often it is confused or combined with the concept of a HostPersonality or conversely the CorePersonality.
There are several issues involved in this concept.
It implies the classic psychological perspective that there was an single personality and that it split into fragments under extreme stress. What if there never was a coherent personality to start with? Aside from the concept that being a Singleton is a delusion and the mind is made up of many parts working together (cf. Minsky's Society of Mind), if the trauma starts early enough (and I am aware of people who's abuse started in utero) then there may not be time for a single coherent personality to form, and thus, no single personality to split (and later Integrate).
Obviously the concept of Hosts complicates the issue by bringing in distinct external entities into the equation.
Within the classic splitting-as-defence-mechanism perspective, there seem to be a few main branches.
- The Common Front is the original, source personality and all the others are "splits" - incomplete fragments there to perform specific tasks, hold particular memories and otherwise help protect the original. The CommonFront is thus treated as the most valuable (being the original) and the desires of others expected to be in support roles. Here the 'original' is treated as if they are the most whole and just need to assimilate the fragments to become complete.
This may be accurate in some cases. In others however it negates the reality and the self awareness and self will of the other members of the multiple.
The original may also actually be the thinest of the personalities, existing as a Veil where most of their experience and emotive capacity is provided by others acting 'through' them. Here the original has gradually been ablated as they have segmented off parts of themselves. This can give them the perspective of being the original but with so many gaps in their experience that they believe themselves insignificant.
- The Core Personality is the original, buried deep in the mind, this perspective envisions the "alters" as rings of protectors, keeping the original safe from harm to the extent it does not actually have any interaction with the outside world.
[Not as clear as I intended. Maybe someone can reorganise it]