This revised edition comes eleven years after the book was first published; the re-writing was done after the author's return to his academic post after five years absence in military service. There has been some reorganization of the material, addition of new material and certain topics have been brought up to date. During the years since the original edition was published there has been a significant development in the field of clinical psychology. Some of this was stimulated by World War II but before this the role of the clinical psychologist had evolved from that of a tester of intelligence levels, a school and vocational adviser, to a diagnostician of personality structure and more recently to that of a therapist. In the preface of the first edition the author noted that the field of clinical psychology can not be limited to psychology as a basic science but is intimately bound up with psychology, medicine, education and sociology. He deplored the lack of an academic curriculum embodying training in each of these fields.