On the other hand, the tradesman, the manufacturer, the professional man, the specialist in every vocation, seeks his clients as the difficulties of travel and communication decrease over an ever-widening area of territory. This is another way in which the mobility of the population may be measured. However, mobility in an individual or in a population is measured, not merely by change of location, but rather by the number and variety of the stimulations to which the individual or the population responds. Mobility depends, not merely upon transportation, but upon communication. Education and the ability to read, the extension of the money economy to an ever-increasing number of the interests of life in so far as it has tended to depersonalize social relations—all these have vastly increased the mobility of modern peoples.
The term mobility, like its correlative, isolation, covers a wide range of phenomena. It may represent at the same time a character and a condition. As isolation may be due to the existence of purely physical barriers to communication, or to a peculiarity of temperament and a lack of education, so mobility may be a consequence of the natural means of communication, or of an agreeable manner and a college education.
It is now clearly recognized that what we ordinarily call a lack of intelligence in individuals, races, and communities, is frequently a result of isolation. On the other hand, the mobility of a population is unquestionably a very large factor in its intellectual development.
There is an intimate connection between the immobility of the primitive man and his so-called inability to use abstract ideas. The knowledge which a peasant ordinarily possesses, from the very nature of his occupation, is concrete and personal. He knows individually and personally every member of the flock he tends. He becomes in the course of years so attached to the land he tills that the mere transposition from the strip of soil on which he has grown up, to another with which he is less intimately acquainted is felt by him as a personal loss. For such a man the neighboring valley, or even the strip of land at the other end of the village is in a certain sense alien territory. A large part of the peasant's efficiency as an agricultural laborer depends upon this intimate and personal acquaintance with the idiosyncrasies of a single plot of land to the care of which he has been bred. It is apparent that under conditions like these, very little of the peasant's practical knowledge will take the abstract form of scientific generalization. He thinks in concrete terms because he knows and needs no other.
On the other hand, the intellectual characteristics of the Jew and his generally recognized interest in abstract and radical ideas are unquestionably connected with the fact that the Jews are, before all else, a city folk. 'The
