Isaacs' simple realistic premise is that because emotion is a built-in mental process, it is always useful. He explores the why and how of those uses. Old questions in psychology are more satisfactorily answered and new questions are asked and answered. Among the many implications of the book we discern a broad panorama of new views about how personality develops, what are psychological health, illness, and effective treatment of disorders. Isaacs includes a never-before achieved clear path to prevention of a broad array of symptom disorders.Because Isaacs controverts hallowed common wisdom and points to defects and scientific weaknesses in all mainstream theories, tradition-bound readers may initially resist the ideas; ideas that for many readers are counterintuitive. An open-minded reading and use of the book may lead readers to conclude this is one of the more important psychology books of our period. This book is for all professionals and students dealing with uses of personality and for lay people interested in understanding the human mind.