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 “Wandering Jew” acquires abstract terms with which to describe the various scenes which he visits. His knowledge of the world is based upon identities and differences, that is to say, on analysis and classification. Reared in intimate association with the bustle and business of the market place, constantly intent on the shrewd and fascinating game of buying and selling, in which he employs that most interesting of abstractions, money, he has neither opportunity nor inclination to cultivate that intimate attachment to places and persons which is characteristic of the immobile person.[9]