THE idea that aggression plays a fundamental role in the development of depression is woven into the fabric of psychiatric thinking. It is half a century since Abraham and Freud first suggested that depression was caused by the introjection of aggressive impulses that had originally been directed externally,1,2 and in spite of the dissenting opinions of Balint,3 Bibring,4 and others, their views are still widely accepted. But Abraham and Freud's hypothesis has a fatal flaw. Like psychoanalytic theory in general, it is formulated in intrapsychic terms. Observable change in the patient's mood or behavior are attributed to intrapsychic events which cannot be observed, only inferred on the basis of the same behavioral changes that they were adduced to explain. As a result, it is incapable of being either confirmed or refuted; after 50 years, there is still no evidence for it or