It is often not just life stress but also a person's idiosyncratic response to life stress that leads to psychopathology. Thus, despite problems in reliability, the validity of defenses makes them a valuable diagnostic axis for understanding psychopathology. By including a patient's defensive style as part of the diagnostic formulation, the clinician is better able to comprehend what seems initially most unreasonable about the patient and to appreciate what is adaptive as well as maladaptive about the patient's defensive distortions of inner and outer reality. Clinical appreciation of the immature defenses (e.g., hypochondriasis, fantasy, dissociation, acting out, projection, and passive aggression) is particularly useful in classifying and caring for individuals with personality disorders.