The biological composition of a group altered by fresh contacts and by intermarriages with members of other groups; and this alteration in biological composition takes place while the language and the social structure of the original group persist little changed. In the United States of America, for instance, language and social institutions are predominantly Anglo-Saxon, far more so than are the racial elements in the population. Ideas and feelings organize themselves in the human mind in sentiments; and in terms of sentiments a great deal of social behaviour can be described. People all recognize the power of such sentiments as love of family, love of nation, attachment to church, class feeling, and such violent aversions as anti-Semitism, anti-clericalism. The history of nations, the history of churches, and much other social history, is the history of the growth, transformation, and decay of collective sentiments.