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 developments 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 International 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").