As the socialization of all mankind advances to ever greater unities, the linguistic limitations sprung from former stages of evolution prove to be a hindrance. The mother tongue, of course, forms the first and most important entry for the individual to the common store of knowledge. But in view of the linguistic limitation of which I have just spoken the efforts in our day are carried on with renewed zeal to create a _universal auxiliary language_ (p. 100) by means of which intercourse should be made possible beyond the language boundaries. There have already been gratifying results.[I] [I] At the present time "Ido" is the best. It is a highly practicable artificial language, and its advocates have succeeded in organizing it to insure its normal development. An older and still rather widespread form called "Esperanto" has failed to organize itself so as to insure its development and it must inevitably die out. =60. Civilization.= Everything which serves the social progress of mankind is appropriately called civilization or culture, and the objective characteristic of progress consists in improved methods for seizing and utilizing the raw energies of nature for human purposes. Thus it was a cultural act when a primitive man discovered that he could extend the radius of his muscle energy by taking a pole in his hand, and it was another cultural act when a primitive man discovered that by throwing a stone he could send his muscle energy a distance of many meters to the desired point. The effect of the knife, the spear, the arrow, and of all the other primitive implements can be called in each case a purposive transformation of energy. And at the other end of the scale of civilization the most abstract scientific discovery, by reason of its generalization and simplification, signifies a corresponding economy of energy for all the coming generations that may have anything to do with the matter. Thus, in fact, the concept of progress as here defined embraces the entire sweep of human endeavor for perfection, or the entire field of culture, and at the same time it shows the great scientific value of the concept of energy.