I haven't read anything particularly recent on this topic, so I have some questions: 1) Does it actually exist, prior to therapy? This may seem like a really stupid question, but there have been papers on the topic that indicated it could be conjured up by the patient's subconscious due to prompting from the psychiatrist. 2) Is it a result of a natural occurance in our mental evolution? As a child's brain evolves, and starts to take on some concept of self, does the child always choose one out of many? Do some children just never choose, and thus spend their lives with distinct -- and possibly conflicting -- personalities? Is one's personality (one's self) just a collection of the common denominator's among all of that one's sub-personalities (this questions could use some explanation, I think: basically, I am not exactly the same person while Mentat on the Physicsforums, as I am while reading in my room, or while at my Kingdom Hall, or while at school, &c...so, could it be that we don't really have a personality, but many sub-personalities that share some common denominators and thus create the illusion of a singular "person")? 3) If so, then where does one draw the line between normal collaboration of sub-personalites, and MPD?