Book excerpt: From the unfaithful husband to the binge eater, from the secret cross-dresser to the pilferer of worthless items, there are those who seem to live two lives, to be divided selves, to be literally of two minds. This division or "vertical split" appears in a person at odds with himself, a person who puzzles over, and even heartily dislikes, that parallel person who behaves in so repugnant a manner. In Being of Two Minds, Arnold Goldberg provides trenchant insight into such divided minds - their origins, their appearances, and their treatment. Goldberg's inquiry into divided minds leads to a return to the psychoanalytic concept of disavowal, which forms the basis of the vertical split. Goldberg explores the developmental circumstances that tend to a reliance on disavowal, provides numerous examples of the emergence of disavowal in the treatment situation, and considers the therapeutic approaches through which disavowal may be addressed. He is especially perceptive in discussing the manner in which the therapist's own tendency to disavow may collusively interact with that of the patient. Goldberg considers the full range of splits to which disavowal gives rise, from circumscribed instances of dissociation to the much-debated multiple personality disorders. He gives special attention to the role of the vertical split in patients with behavior disorders; here his thoughtful insights point to a treatment approach that significantly differs both from the simple ascription of a 'self disorder' and from the usual pedagogical emphasis on issues of self-control and/or punishment. As Goldberg shows, the repugnance felt by many therapists for offensive behaviors emanating from the patient's parallel self are frequently shared by the patient, who commonly despises misbehavior that he is unable to understand. Being of Two Minds begins to formulate just such understanding, to the great benefit of patient and therapist alike.