The term multiple personality does refer to the most striking feature of the disorder, but it also misplaces the emphasis. The key to making sense of dissociative identity disorder is to look not at the personalities but at the memory barriers between them. We could describe a house in two ways, either as a collection of rooms or as a collction of walls. Both are true, but one cannot construct a house out of rooms. Only walls can be constructed, and rooms are the result. When we first confront multiple personality, we see dramatically different personalities before our eyes. We see rooms, and it is easy to forget that their existence is really a consequence of there being walls- that is, dissociative memory barriers resulting from trauma.
As memory barriers become fixed and are maintaned over time, the personalities on opposite sides develop separate histories, values, allegiances, possessions, and relationships. All of us have different sides to ourselves. Multiples are not unique in this way. The difference is that “singletons”, as multiples sometimes call the rest of us, have a shared consciousness and memory. We, too, have different facets or parts of themselves, but our sense of our own identity is unitary.
Jeffery Smith M.D.
from A Fractured Mind by Robert B Oxnam