Theorists who endorse the concept of symptom substitution reject treatments of psychopathology that do not address the underlying causes of symptoms. They hypothesize that such treatments lead to worsening or relapsing of original symptoms, or the substitution of new for old symptoms. In contrast to behavioristic approaches that dispute this hypothesis, Ellis accepts the concept of symptom substitution. Unlike the psychodynamic positions which are credited with the concept, however, rational-emotive therapy (RET) focuses on changing underlying irrational philosophies and beliefs. Symptom substitution is believed to be prevented in RET by teaching clients to dispute irrational thinking in an ongoing way.