One narrative technique for consolidating the gains a client makes involves a therapist writing letters to the person. this is documenting the evidence.Basically, the externalization of a problem consists in the linguistic separation of the problem of the personal identity of the client.In recent years, therapists around the world have begun to evaluate the narrative approach, reducing the weight of the traditional client-therapist relationship and treating the concept of personal identity as a fluid social construction. The appeal of this Narrative Therapy goes beyond the technique, since it represents a fundamental change of direction in the therapeutic world that has been called the Third Wave.