In the first chapter the writer gives us his definition of society as "any group or number of individuals who cultivate acquaintance and mental agreement--that is to say, like-mindedness." The unit of investigation in sociology is declared to be the individual member of society, or, as the writer calls him, in relation to the investigation in hand, the "socius." Whether in strict logic the unit of investigation in _sociology_ can be the individual, even granting, as must be done, that he is born social, is a point on which we are not fully satisfied. We should be disposed to think that the study of the individual was rather what Mr. Spencer would call a "preparation" for sociology than an integral part of the science itself. From a practical point of view, however, it must be conceded that a treatise on sociology would begin somewhat abruptly if it did not present in the first place an adequate description of the "socius," especially setting forth those qualifications and tendencies which fit and impel him to enter into relations with other members of the human race. Chapter V of the present work deals with The Practical Activities of Socii, and shows in an interesting manner what may be called the lines of approach of individuals to one another in society. Sometimes the approach is by means of conflict, and the writer shows how this may be a preparation for peaceful relations through the insight it gives into opposing points of view. He distinguishes between primary and secondary conflict--the first being a struggle in which one individual violently strives to suppress or subdue an opposing personality, the second a mere trial of differing opinions and tastes, leading often to a profitable readjustment of individual standpoints.