This study of human nature has been written with the conviction that every man desires fullness of life, hence is willing to undertake any investigation which promises to put him in surer command of his resources. It endeavors to disclose various lines of development in such a way as to arouse enthusiasm for one of the most fascinating subjects that ever engage human attention the study of the human mind. In so doing no attempt is made to persuade the reader that there is one, and only one road to success, one theory or principle of interpretation. The purpose of the book is rather to aid each reader to investigate for himself, and advance from the point already attained. Hence while the book is offered as a contribution to the science of human nature, it is first of all practical.