In a recent article in the Schizophrenia-Bulletin, Goplerud and Depue (1978) discuss our writings on postpsychotic depression (McGlashan and Carpenter (1976a and 1976b). They argue that postpsychotic depression is the depressed phase of bipolar affective illness and thus join many workers who now challenge the diagnosis of schizophrenia in patients in whom affective disturbance is a significant part of the manifest psychopathology. In our response, we place special emphasis on the fallacy of using nondiscriminating similarities between groups (e.g., suicidal ideation) as a basis for positing disease homogeneity. Contrariwise, we argue the value of emphasizing nosologically discriminating features of individual patients in reaching diagnostic decisions.