Twenty years is a long time in the life of a science. While the historical roots of psychology have not changed since the first edition of this book, some of the offshoots of the various theories and systems discussed have been crit ically reexamined and have undergone far-reaching modifications. New and bold research has led to a broadening of perspectives, and recent devel opments in several areas required a considerable amount of rewriting. I have been fortunate in the last fifteen years to have worked with about 2,000 psychologists and other behavioral scientists who contributed to several collected volumes I have edited. As the editor-in-chief of the In ternational Encyclopedia of Psychiatry, Psychology, Psychoanalysis and Neurol ogy, I have had the privilege of reading, scrutinizing, and editing the work of 1,500 experts in psychology and related disciplines. In addition, I have written several books and monographs and over one hundred scientific papers. Armed with all that experience, I have carefully examined the pages of the first edition. Chapter 8 required substantial rewriting and several new sections have been added to other chapters: Current Soviet Psychol ogy (Chapter 2, Section 7); New Ideas on Purposivism (Chapter 5, Sec tion 4); Recent Developments in the Sociological School of Psychoanalysis (Chapter 9, Section 4); and Present Status of Gestalt Psychology (Chapter 12, Section 4). Chapter 15 was omitted, and two new chapters were added: Chapter 14 (Humanistic Psychology) and Chapter 16 (Selected Research Areas).