The author is not unaware of the new theories concerning the parallelism of human development by which it is contended that absolute uniformity of man's thoughts and actions, aims and methods, is produced when he is in the same degree of development, no matter in what country or in what epoch he lives. This theory has been pushed until it has been said, nothing but geographical environment seems to modify the monotonous sameness of man's creations. The author does not accept this theory, yet he does not here controvert it. It may be true to a certain extent, but it surely has its limitations, and it is only applicable under special conditions. As a general proposition, it might apply to races and peoples but not to individuals. If it builds on the hereditary human instincts, it does not take into account the will, energy, and reasoning powers of man. Most of all, it leaves out the egoism of man and his selfish desire for power, improvement, and happiness, and all their effects, through the individual, on human progress. In the author's opinion the progress of peoples through consecutive stages of civilization is entirely compatible with his belief that knowledge of specific objects, the uses of material things, the performance of certain rites, the playing of certain games, the possession of certain myths and traditions, and the carrying on of certain industries, passed from one country to another by migration of their peoples, or by contact or communication between them; and that the knowledge, by separate peoples, of the same things, within reasonable bounds of similarity of action and purpose, and with corresponding difficulty of performance, may well be treated as evidence of such migration, contact, or communication. Sir John Lubbock expresses the author's belief when he says,[315] "There can be no doubt but that man originally crept over the earth's surface, little by little, year by year, just, for instance, as the weeds of Europe are now gradually but surely creeping over the surface of Australia." The word migration has been used by the author in any sense that permitted the people, or any number thereof, to pass from one country to another country, or from one section of a country to another section of the same country, by any means or in any numbers as they pleased or could.