"Two souls, which take possession of my bodily frame by turns, the one being all unconscious of what the other performs"

The experiences Robert describes are strongly reminiscent of what would now be called dissociative identity disorder. This term, which has replaced multiple personality disorder in medical diagnoses, describes a condition in which a person has more than one personality state. These different personalities, which take it in turns to assert control over the individual, are quite distinct from each other: they have different names, memories, self-images and sometimes ages, genders, races and sexual orientations. Switches between personalities are often triggered by stressful events. DID sufferers usually have a main personality referred to as the ‘host’; whilst other identities are in control, the host will not have any awareness of themselves and for this reason patients experience long periods of amnesia. Recognition between personalities varies from patient to patient.