We use parts langage in part because our therapist does. She doesn't support the idea that we are separate people and in session she serves as an anchor to this external reality. And I need that. I want her to treat all of us in the context of our combined and often contradictory experiences and beliefs.
Dissociative patients often have what is called psychic equivalence—that is, they experience internal reality (dissociative parts, flashbacks, even thoughts or emotions) as real and powerful external realities (Fonagy, Gergely, Jurist, & Target, 2005; Target & Fonagy, 1996). While Fonagy et al. (2005) have described psychic equivalence as a failure to mentalize, it is also due to the extreme hypnotic trance logic common in dissociative patients, in which critical thinking and logic are suspended (e.g., Orne, 1959; Kluft, 1982; see Chapter 8).
Thus, they may view parts as real people instead of disowned parts of the self. They experience flashbacks as real events in the present instead of as memories of the past. They may literally perceive the therapist as the abuser because they feel abused. They may take their strong feeling of being bad as unbearable evidence that they are bad. Therapists must not engage in psychic equivalence in regard to dissociative parts—that is, they must not confuse the patient’s dissociative parts that are manifestations of extreme non-realization with actual people who should be treated separately and differently from each other.