Other personalities are created to handle new traumas, their existence usually occurring one at a time. Each has a singular purpose and is totally focused on that task. The important aspect of the mind's extreme dissociation is that each ego state is totally without knowledge of the other. Because of this, the researchers for the CIA and the Department of Defense believed they could take a personality, train him or her to be a killer and no other ego stares would be aware of the violence that was taking place. The personality running the body would be genuinely unaware of the deaths another personality was causing. Even torture could not expose the with, because the personality experiencing the torture would have no awareness of the information being sought. Earlier, such knowledge was gained from therapists working with adults who had multiple personalities. The earliest pioneers in the field, such as Dr. Ralph Alison, a psychiatrist then living in Santa Cruz, California, were helping victims of severe early childhood trauma. Because there were no protocols for treatment, the pioneers made careful notes, publishing their discoveries so other therapists would understand how to help these rare cases. By 1965, the information was fairly extensive, including the knowledge that only unusually intelligent children become multiple personalities and that sexual trauma endured by a restrained child under the age of seven is the most common way to induce hysteric dissociation.

~ Lynn Hersha

A man who lives a part, not to others but alone, is exposed to obvious psychological dangers. In itself the practice of deception is not particularly exacting. It is a matter of experience, a professional expertise. It is a facility most of us can acquire. But while a confidence trickster, a play actor or a gambler can return from his performance to the ranks of his admirers, the secret agent enjoys no such relief. For him, deception is first a matter of self defense. He must protect himself not only from without, but from within, and against the most natural of impulses. Though he earn a fortune, his role may forbid him the purchase of a razor. Though he be erudite, it can befall him to mumble nothing but banalities. Though he be an affectionate husband and father, he must within all circumstances without himself from those with whom he should naturally confide. Aware of the overwhelming temptations which assail a man permanently isolated in his deceit, Limas resorted to the course which armed him best. Even when he was alone, he compelled himself to live with the personality he had assumed. It is said that Balzac on his deathbed inquired anxiously after the health and prosperity of characters he had created. Similarly, Limas, without relinquishing the power of invention, identified himself with what he had invented. The qualities he had exhibited to Fiedler: the restless uncertainty, the protective arrogance concealing shame were not approximations, but extensions of qualities he actually possessed. Hence, also, the slight dragging of the feet, the aspect of personal neglect, the indifference to food, and an increasing reliance on alcohol and tobacco. When alone, he remained faithful to these habits. He would even exaggerate them a little, mumbling to himself about the iniquities of his service. Only very rarely, as now, going to bed that evening, did he allow himself the dangerous luxury of admitting the great lie that he lived.

~ John Le Carré