The individual man is the bearer of a double inheritance. As a member of a race, he transmits by interbreeding a biological inheritance. As a member of society or a social group, on the other hand, he transmits by communication a social inheritance. The particular complex of inheritable characters which characterizes the individuals of a racial group constitutes the racial temperament. The particular group of habits, accommodations, sentiments, attitudes, and ideals transmitted by communication and education constitutes a social tradition. Between this temperament and this tradition there is, as has been generally recognized, a very intimate relationship. My assumption is that temperament is the basis of the interests; that as such it determines in the long run the general run of attention, and this, eventually, determines the selection in the case of an individual of his vocation, in the case of the racial group of its culture. That is to say, temperament determines what things the individual and the group will be interested in; what elements of the general culture, to which they have access, they will assimilate; what, to state it pedagogically, they will learn. It will be evident at once that where individuals of the same race and hence the same temperament are associated, the temperamental interests will tend to reinforce one another, and the attention of members of the group will be more completely focused upon the specific objects and values that correspond to the racial temperament. In this way racial qualities become the basis for nationalities, a nationalistic group being merely a cultural and, eventually, a political society founded on the basis of racial inheritances. On the other hand, when racial segregation is broken up and members of a racial group are dispersed, the opposite effect will take place. This explains the phenomena which have frequently been the subject of comment and observation, that the racial characteristics manifest themselves in an extraordinary way in large homogeneous gatherings. The contrast between a mass meeting of one race and a similar meeting of another is particularly striking. Under such circumstances characteristic racial and temperamental differences appear that would otherwise pass entirely unnoticed.