Mentalization, the capacity to understand the mental state of oneself and others which underlies overt behaviour,is a developmental achievement through the context of attachment relationship during infancy and childhood. Mentalization based treatment（MBT）is a psychotherapy that promote the further development of mentalizing. MBT for borderline personality disorder（BPD）, developed and manualised by Peter Fonagy and Anthony Bateman,is well-known. According to them,vulnerability to a loss in mentalizing particularly in interpersonal or stressful circumstances is a core feature of BPD. For these patients, traditional psychotherapy would produce iatrogenic harms rather than some improvements.
 To avoid those iatrogenic effects, MBT therapist takes the stance of “not-knowing”. Therapist stimulates the patient’s mentalizing,and makes the patient have some inquisitiveness about the mental states of oneself and others. For this purpose,the triad of“event-beliefaffect”is explored. At first, the problematic act of the patient is detected. Secondly, rewinding to the time when that problematic act has arisen,the therapist collaborate with the patient to identify the event that provokes the failure of mentalization, and to clarify the affect of patient at the moment. Thirdly, to gain alternative perspectives, that situation is explored through the emotional context. Finally,the specific maladaptive belief which causes a disruption of mentalizing is identified. When the same pattern of mentalizing failure is occurred in the process of the therapy, it was brought up in the “here and now”relationship between the patient and therapist.
 As seen above,MBT,which explores the relationship between affect and belief,has some technical features similar to cognitive behaviour therapy, which explores the relationship between maladaptive schema and dysfunctional cognition or problematic feeling. However, to the extent of focusing on the “here and now”relationship between patient and therapist, and of placing an emphasis on the context of transference, MBT is still psychodynamic psychotherapy.