In The Psychotherapy of Personality Disorders, Lisa J. Cohen introduces Emergent Systems Theory, an integrative model of the many different types of psychotherapy, with an emphasis on personality pathology. This model proposes five general levels of the mind/brain, each of which dates back to a different point in human evolutionary history and has its own distinct psychological functions and psychopathology. This book argues that formulating patients’ psychological difficulties in terms of the levels involved permits systematic selection of the most appropriate treatments and can also enhance communication across the mental health field.