_Progress Is Enhanced by the Interaction of Groups and Races_.--The accumulation of civilization and the state of progress may be much determined by the interaction of races and groups. Just as individual personality is developed by contact with others, so the actions and reactions of tribes and races in contact bring into play the utility of discoveries and inventions. Thus, knowledge of any kind may by diffusion become a heritage of all races. If one tribe should acquire the art of making implements by chipping flint in a certain way, other tribes with which it comes in contact might borrow the idea and extend it, and thus it becomes spread over a wide area. However, if the original discoverer used the chipped flint for skinning animals, the one who would borrow the idea might use it to make implements of warfare. Thus, through borrowing, progress may be a co-operative process. The reference to people in any community reveals the fact that there are few that lead and many that follow; that there is but one Edison, but there are millions that follow Edison. Even in the educational world there are few inventors and many followers. This is evidence of the large power of imitation and adaptation and of the universal habit of borrowing. On the other hand, if one chemical laboratory should discover a high explosive which may be used in blasting rock for making the foundations for buildings, a nation might borrow the idea and use it in warfare for the destruction of man. Mr. Clark Wissler has shown in his book on _Man and Culture_ that there are culture areas originating from culture centres. From these culture centres the bow-and-arrow is used over a wide area. The domestication of the horse, which occurred in central Asia, has spread over the whole world. So stone implements of culture centres have been borrowed and exchanged more or less throughout the world. The theory is that one tribe or race invented one thing because of the {27} adaptability to good environment. The dominant necessity of a race stimulated man's inventive power, while another tribe would invent or discover some other new thing for similar reasons. But once created, not only could the products be swapped or traded, but, where this was impossible, ideas could be borrowed and adapted through imitation.