In modern civilization the increasing attractiveness of the city is one of the apparent social facts.[6] Social psychology may reasonably be expected to throw light upon the causes of this movement of population from rural to urban conditions of life. Striking illustrations of individual preference for city life, even in opposition to the person's economic interests, suggest that this problem of social behavior so characteristic of our time contains important mental factors. Since sensations give the mind its raw material,[7] the mind may be said to crave stimulation. "In the most general way of viewing the matter, beings that seem to us to possess minds show in their physical life what we may call a great and discriminating sensitiveness to what goes on at any present time in their environment."[8] This interest of the mind in the receiving of stimulation for its own activity is an essential element in any social problem. The individual reacts socially "with a great and discriminating sensitiveness" to his environment, just as he reacts physically to his stimuli to conserve pleasure and avoid pain. The fundamental sources of stimuli are, of course, common to all forms of social grouping, but one difference between rural and urban life expresses itself in the greater difficulty of obtaining under rural conditions certain definite stimulations from the environment. This fact is assumed both by those who hold the popular belief that most great men are country-born and by those who accept the thesis of Ward that "fecundity in eminent persons seems then to be intimately connected with cities."[9] The city may be called an environment of greater quantitative stimulations than the country. The city furnishes forceful, varied, and artificial stimuli; the country affords an environment of stimuli in comparison less strong and more uniform. Minds that crave external, quantitative stimuli for pleasing experiences are naturally attracted by the city and repelled by the monotony of the country. On the other hand, those who find their supreme mental satisfactions in their interpretation or appreciation of the significant expression of the beauty and lawfulness of nature discover what may be called an environment of qualitative stimulations. The city appeals, therefore, to those who with passive attitude need quantitative, external experiences; the country is a splendid opportunity for those who are fitted to create their mental satisfactions from the active working over of stimuli that appear commonplace to the uninterpreting mind. If Coney Island, with its noise and manufactured stimulations, is representative of the city, White's "Natural History of Selborne" is a characteristic product of the wealth of the country to the mind gifted with penetrating skill.