Introduction Modern psychiatry recognizes three major sources of influence on the psychopathology of the individual patient: the physiologic, the psychologic, and the sociologic. This triadistic approach is not rigorously adhered to by every psychiatrist or by every school of psychiatry, but even the most loyal proponent of the organic, the psychodynamic, or the environmentalist viewpoint usually at least acknowledges the actual or potential importance of one or both of the other two approaches. In clinical practice psychiatrists have for many years utilized a three-pronged attack on mental disease, attempting to alter physiologic influences by, for example, pharmacologic agents, and to change psychologic and sociologic influences by psychotherapy and manipulation of the environment. As knowledge advances in each of these areas, of course, the clinician is in a better position to alter favorably the course of his patient's illness. We are currently concerned with one aspect of this problem: What is