This book encompasses the latest established principles and the latest theories advanced in the field of abnormal psychology. The background for these principles and discoveries is set by a brief discussion of the history of the subject. Although this is a symposium consisting of twenty-four chapters, written by different authors, the subject matter has been arranged in such a way as to develop and elaborate upon the subject in proper sequence. Each chapter has been edited to provide uniformity and simplicity of exposition. As in most instances of a symposium type book, some chapters are better than others, but on the whole the selection of subjects presented was of great importance. The discussions were in general interesting, well treated and valuable. The method of approach and language are clear enough to render this book valuable to the lay person and to the student who would seek to keep abreast of the latest findings in the search for the causes and meaning of abnormal psychology.