_The Efforts of Man to Satisfy Physical Needs_.--All knowledge of primitive man, whether derived from the records of cultures he has left or assumed from analogy of living tribes of a low order of civilization, discovers him wandering along the streams in the valleys or by the shores of lakes and oceans, searching for food and incidentally seeking protection in caves and trees. The whole earth was his so far as he could appropriate it. He cared nothing for ownership; he only wanted room to search for the food nature had provided. When he failed to find sufficient food as nature left it, he starved. So in his wandering life he adapted himself to nature as he found it. In the different environments he acquired different customs and habits of life. If he came in contact with other tribes, an exchange of knowledge and customs took place, and both tribes were richer thereby. However, the universality of the human mind made it possible for two detached tribes, under similar environment and similar stimuli, to develop the same customs and habits of life, provided they had the same degree of development. Hence, we have independent group development and group borrowing. When nature failed to provide him with sufficient food, he learned to force her to yield a larger supply. When natural objects were insufficient for his purposes, he made artificial tools to supplement them. Slowly he became an inventor. Slowly he mastered the art of living. Thus physical needs were gradually satisfied, and the foundation for the superstructure of civilization was laid. _The Attempt to Satisfy Hunger and to Protect from Cold_.--To this statement must be added the fact that struggle with {83} his fellows arose from the attempt to obtain food, and we have practically the whole occupation of man in a state of savagery. At least, the simple activities represent the essential forces at the foundation of human social life. The attempt to preserve life either through instinct, impulse, emotion, or rational selection is fundamental in all animal existence. The other great factor at the foundation of human effort is the desire to perpetuate the species. This, in fact, is the mere projection of the individual life into the next generation, and is fundamentally important to the individual and to the race alike. All modern efforts can be traced to these three fundamental activities. But in seeking to satisfy the cravings of hunger and to avoid the pain of cold, man has developed a varied and active life. About these two centres cluster all the simple forces of human progress. Indeed, invention and discovery and the advancement of the industrial arts receive their initial impulses from these economic relations.