This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book aims to provide students, therapists, educators, and individuals interested in furthering the field of psychotherapy with an opportunity to review brief therapy in relation to attachment disorders in the light of what is becoming known in neuroscience. It also provides an overview of brief therapy in the twenty-first century and a summary of the main brief therapies. The book describes an integration of the current understanding within outcome orientated and brief therapies, of core belief structures, and the theories of object relations and attachment disorder. Cognitive analytic therapy (CAT) is an integrated model of psychotherapy that is underpinned by object relations theory and Kelly’s personal construct theory. The aim of CAT is to enable clients to understand and manage selflimiting beliefs and emotional states by identifying, working with, and changing these patterns of expression.