This emphasis upon the instincts reaches an extreme form in W. Trotter’s _Instincts of the Herd in Peace and War_, where the herd instinct is made all-dominant. According to Mr. Trotter the herd instinct arouses fear in the individual and rules him through rigorous conventional means--in a large percentages of cases to his detriment. In conjunction with his theory of instincts, Professor McDougall has advanced a noteworthy conception of the sentiments. The three leading expressions of sentiment are love, hate, and respect. Sympathy is regarded as an elemental sentiment, in fact, as an emotion in its simplest form. A sentiment is “an organized system of emotional tendencies centered about some object.” The sentiments comprise an important phase of the self, and function powerfully in determining social conduct. It was in 1901 that Professor E. A. Ross made his initial contribution to psycho-sociologic thought--seven years before his _Social Psychology_ was published. His first great work was _Social Control_. In this excursus he defined social psychology as the study of “the psychic interplay between man and his environing society.”[XXIII-20] This interplay is two-fold: the domination of society over the individual (social ascendancy); and the domination of the individual over society (individual ascendancy). Social ascendancy may be either purposeless (social influence) or purposeful (social control). Social psychology, according to Professor Ross, deals with psychic planes and currents; it does not treat of groups, which is a part of the preserve of psychological sociology. The psycho-sociologic grounds of control are found in such factors as sympathy, sociability, an elemental sense of justice, and particularly in group needs. There are individuals whose conduct exasperates the group. “In this common wrath and common vengeance lies the germ of a social control of the person.”[XXIII-21] Perhaps the best part of Professor Ross’ discussion of social control is his analysis of the agents of control.[XXIII-22] Public opinion and law are the two most important means of controlling individuals. The weakness of one, in this connection, is its fitfulness; of the other, its rigidity. Personal beliefs and ideals function widely and effectively because of their subjective character. An individual may escape the operation of law; he can hide away from the winds of public opinion; but he cannot get away from his own ideas and conscience. It is for this reason that religious convictions are powerful. Art as a means of social control is commonly underrated. It arouses the passions, kindles sympathies, creates a sense of the beautiful and perfects social symbols, such as Columbia, La Belle France, Britannia.[XXIII-23]