The author explores the intersubjective aspect of the devolution of melancholia into psychosis, particularly as it involves the unconscious intersubjective role of the mother. The author considers the possibility that maternal inability to mourn contributes significantly to the foreclosure of the child's “tertiary processes” (the processes involved in the child's development of a differentiated autonomous self and symbolization). In the clinical case presented in detail in this paper, the child's undifferentiated experience with his mother (who was unable to grieve) left no room for the father as the necessary third element in the child's maturational processes.