Rational-Emotive Therapy (RET) is predicated on a theory of causality. According to Ellis (1962), beliefs regarding an event, and not the event itself, cause emotional reactions. Mentally healthy persons practice this reational theory of causality. Neurotic persons accept an irrational theory of causality based on coincidental or correlational data. Therapeutic change occurs when irrational theories are tested, refuted, and replaced by rational ones. The ontogenetic development of theories of causality as described by Piaget (1952, 1954, 1960) parallels therapeutic development. Young children possess irrational theories of causality. As they mature, their experiences within a natural environment refute the irrational theories and lead to the development of rational ones. The similarities between developmental and therapeutic progress suggest that rational-emotive educators must be knowledgeable in both cognitive developmental theories and the RET framework. (NRB)