This book is primarily a study of Man and ultimately embraces all the great qualities and problems of Man. As a study of Man it takes into consideration all the characteristics which make Man what he is. If some readers do note the absence of certain expressions familiar to them, it does not mean that the author does not feel or think as many other people-he does-and very much so; but in this book an effort has been made to approach the problem of Man from a scientific-mathematical point of view, and therefore great pains have been taken not to use words insufficiently defined, or words with many meanings. The author has done his utmost to use such words as convey only the meaning intended, and in the case of some words, such as "spiritual," there has been superadded the word "so-called," not because the author has any belief or disbelief in such phenomena; there is no need for beliefs because some such phenomena exist, no matter what we may think of them or by what name we call them; but because the word "spiritual" is not scientifically defined, and every individual understands and uses this word in a personal and private way. To be impersonal the author has had to indicate this element by adding "so-called." I repeat once again that this book is not a "materialistic" or a "spiritualistic" book-it is a study of "Man" and therefore does and should include materialistic as well as spiritual phenomena because only the complex of these phenomena constitutes the complex of Man.