Density of population is determined by the combination of two factors, namely the birth rate and the migration rate. No community of large dimensions is a purely genetic aggregation, maintained wholly by its birth rate. It is at the same time a congregation, a group brought to gether in part by the incoming of individuals or families born in other parts. Genetic aggre gation itself is more or less complicated by variation, and this, in combination with the re sults of migration, gives rise to a composition of the population of elements more or less un like. The physical differences thus comprised include organic variation, differences of age, the difference of sex, and the degrees of kinship. The degrees of kinship include consanguinity, or the nearest degree of blood relationship; pro pinquity, the somewhat remoter degree of neigh boring communities that have much intermar ried; nationality, the kinship of those who from their birth have been of the same speech and political association; potential nationality, or nationality in the making; ethnic race, glottic race, chromatic race, and eephalic race.
These compound race terms are used to avoid confusion. Ethnic race includes those nearly related nationalities which speak closely related languages and exhibit common psychological characteristics. For example. the Teutonic race includes the Saxon-English, the Dutch, the Ger mans, and the Scandinavians, all related na tionalities. The glottic race is a yet broader kinship which includes those related ethnic races which at some remote period had a common cul ture and spoke the same language, as, for ex ample, the Aryan glottic race, which includes the Teutons, the Celt, the Latins, and the Slays. Chromatic race is that remote degree of relation ship which includes all glottic races of the same general color of the skin and type of hair. Cephalic race is that most remote degree of kin ship which is manifested in peculiarities of cranial structure. There are various gradations from the dolichocephalie. or long head of the negro, to the brachycephalic. or broad head of the Mongol.
The influence of the physical environment is seen in the degrees to which a population is heterogeneous, no less than in the degree of den sity. The causation, however. is perhaps more in direct. 'Naturally isolated regions, and regions that offer no great temptation to immigration, remain relatively homogeneous. Agricultural regions remain more homogeneous in population than mining regions or points of commercial or industrial opportunity. of great agricultural fertility which share also in other advantages have usually in the world's history become heterogeneous in population through another cause also besides immigration. Armed invasion and conquest have brought differing, often alien, races into enduring contact, and their relations have commonly been determined more directly than has generally been supposed by the physical environment, which has caused a scat tering or a concentration of the invaders or of the invaded, or of both. Sooner or later, what ever the admixture of nationalities and races, a large degree of amalgamation takes place in every population through intermarriage. While external influences may be tending to make a social population composite, its own internal forces work toward homogeneity and unity.
(2) The gocial ifind.—The evolution of the
social mind is determined by those physical facts of the density and composition of a social popula tion which condition its subjective life. The more homogeneous a population is the more certainly will its individuals be moved by common im pulses. Heterogeneous populations have varied interests, which is another way of saying that they respond to differing stimuli. Again, the va riety and intensity of the stimuli themselves are determined partly by the environment, and partly by the demotic composition.
The like responses from which social activities are developed are temporary or habitual, and the stimuli of temporary like responses include near ly all of the initial causes of association. Where the stimuli are persistent and lead to habitual conduct the whole nervous organization is mold ed accordingly. Mental and practical resem blances are created. The stimuli presented by external nature create types of emotion and of intellect. The stimuli of economic opportunity, leading to activities of utilization, create types of disposition. The stimuli which impel men to adapt themselves to their environment, when they have failed to adapt the environment to themselves, create types of character. Types of emotion, intellect, disposition, and character in their various combinations make up the vari ous types of mind.
The important types of intellect are (1) those in which judgment is determined subjectively, by instinct, habit, and auto-suggestion; (2) those in which it is objectively determined, by ex ternal suggestion : (3) those in which it is subjectively determined, by emotion, mood, and temperament; and (4) those in which it is ob jectively determined, by evidence. The types of disposition are (1) the aggressive; (2) the in stigative (which, instead of directly attacking, commanding, or inventing, tries to achieve the purposes of life by working through other men by suggestion, temptation, or persuasion) ; (3) the domineering (the disposition of those who have the power to impress others, and who love to assert authority) ; and (4) the creative, the disposition of those who assume responsibility and convert ideas into realities. The types of character are (1) the forceful, directly created by the struggle for existence which eliminates weaklings: (2) the convivial, which emerges when the struggle for existence has been so far successful that men may relax their efforts and devote themselves to pleasure; (3) the austere, which is produced by reaction against the ex cesses of the convivial; and (4) the rationally conscientious. which is produced by reaction against the excesses of the austere. The types of mind are (1) the ideo-motor, the activities of which are for the most part instinctive; (2) the ideo-emotional, which is emotional (rather than physically active), imaginative, suggestible, instigative. and convivial; (3) the dogmatic emotional, marked by an extreme development of preferential attention, devotion to a dominant idea or belief, intolerance. domineering disposi tion, and austere character; (4) the critical intellectual, in which the ideo-motor, ideo-emo tional, and dogmatic emotional activities, always present in combination, are habitually kept under the control of a critical and vigilant in tellect, and in which disposition is creative and character rationally conscientious.