CONDITIONS OF DEVELOPMENT. 245 



It is a matter of common observation that the 

 human mind will not develop to full power without a 

 certain amount of stimulus from its surroundings, — 

 without something to urge it to activity. All sys- 

 tems of primary education are based upon this fact ; 

 and even after the schools have done their work, 

 unless some change of conditions of life, infusion 

 of new ideas, or adversity and misfortune, occur 

 to compel the mind to great activity, it will not 

 attain its greatest development. It will not only 

 lack the power of rapid calculation and compre- 

 hensive judgment, but will be narrowed in the range 

 of its feelings, and wanting altogether in certain 

 sympathies. A general proof of this is furnished 

 by comparing the average mental development of 

 those who, having no high intellectual interests, 

 live always without change in quiet villages and 

 on farms, with the development of those who dwell 

 in cities and also travel. We see also that the 

 mind and the brain — its physical mechanism — 

 not only need an active stimulus from the environ- 

 ment to attain their normal development, but need 

 constantly new stimuli to retain those powers in 

 perfection. This principle has a very wide and 

 important application, as can be seen by reviewing 

 the conditions necessary to the development of 

 animals. They all require the action of stimuli 



