This book is intended to serve as an introduction to the study of human behivor. The author has therefore attempted to present a brief outline in a form favorable for discussion and investigation. The importance of the subject is obvious and has been tragically emphasized by the present world crisis. Little is known about man as he is. Imagination has supplied many of the details in the picture of what he was once supposed to be, while disappointment associated with unrealized expectations of what he might have become has increased the difficulties of taking measure of his present stature. Parent, teacher, physician, student of social phenomena, prospective reformer, statesman and philosopher, each has his special interest in the general human problem. To-day every intelligent citizen is anxiously awaiting the solution to the problem of how "democracy may be made safe for the world". There can be little doubt that in the careful, painstaking study of man as he is will be found the means by which human institutions may be established upon a more rational basis and at least an intelligent effort made to lay the foundations of a durable peace.