SD is a theory put out there for people who resort to having to use 'parts' due to past trauma experiences. It is usually something that happens because of trauma in the developmental years. Again, it is a theory. Seems pretty sound though. Many trauma therapists speak of 'parts'.
So for instance, I used to have a 'part' of me that ran outside in the freezing cold and laid down in ditches (to die I am assuming). I have no attachment (myself) to ditches whatsoever. No idea why I did that but it was really freaking dramatic and scary as crap for those around me. Myself? While in this 'ditch seeking part', I wasn't scared at all. Nor was the 'observer' who would try to talk this part into getting out of the ditch. No real emotion. Just an incredible need for safety that is many times conflicting with a 'immediate' need for safety that the part can't see.
So for instance, I used to have a 'part' of me that ran outside in the freezing cold and laid down in ditches (to die I am assuming). I have no attachment (myself) to ditches whatsoever. No idea why I did that but it was really freaking dramatic and scary as crap for those around me. Myself? While in this 'ditch seeking part', I wasn't scared at all. Nor was the 'observer' who would try to talk this part into getting out of the ditch. No real emotion. Just an incredible need for safety that is many times conflicting with a 'immediate' need for safety that the part can't see.