The central ideas making up Harry Stack Sullivan's theory of personality find their first expression in this book. Here he set forth his view of psychiatry as the study of interpersonal relations. "Psychiatry," he wrote, "is the study of processes that involve or go on between people. The field of psychiatry is the field of interpersonal relations under any and all circumstances in which these relations exist. A personality can never be isolated from the complex of interpersonal relations in which the person lives and has his being." Through his development of the theory of interpersonal relations, Harry Stack Sullivan not only made a vital contribution on the treatment of mental disorder—in particular, schizophrenia—but he opened an entirely new approach to the study of human personality. "The core of Sullivan's theory," says Lloyd Frankenberg in the New York Times, "is that people, interacting, shape people....He has evolved an analytic method, for all its subtlety and elaboration, wonderfully coherent, organic and usable." The influence of Harry Stack Sullivan has had a powerful impact. He has been called one of the half dozen truly great figures in American social psychology, one who has opened new horizons of research and, in the view of many analysist, made the most original contribution to psychiatry since Freud.