Loneliness, one of our least satisfactorily conceptualized phenomena, has been relegated to philosophy and sociology, and when confronted in the therapy session, has been subsumed under depression and treated as if it were depression. However, loneliness is a separate entity with unique characteristics that need to be identified and treated appropriately. Loneliness is a state in which one feels incomplete. The primary affect is longing, whereas in depression, the salient affect is anger. Unlike the depressive, the lonely individual reaches out but can never communicate and, consequently, never quell the longing. An understanding of this constellation makes the identification of loneliness as the primary symptom the prerequisite for treatment. (Author)