_The Elementary Ideas and their Development._—These two principles, or rather demonstrated truths,—the unity of the mind of man, and the substantial uniformity of its action under like conditions,—form the broad and secure foundation for Ethnic Psychology. They confirm the validity of its results and guarantee its methods.
As there are conditions which are universal, such as the structure and functions of the body, its general relations to its surroundings, its needs and powers, these developed everywhere at first the like psychical activities, or mental expressions. They constitute what Bastian has happily called the “elementary ideas” of our species. In all races, over all continents, they present themselves with a wonderful sameness, which led the older students of man to the fallacious supposition that they must have been borrowed from some common centre.
Nor are they easily obliterated under the stress of new experiences and changed conditions. With that tenacity of life which characterises simple and primitive forms, they persist through periods of divergent and higher culture, hiding under venerable beliefs, emerging with fresh disguises, but easily detected as but repetitions of the dear primordial faiths of the race.
_The Ethnic Ideas and their Origin._—From the monotonous unity of the elementary ideas, the common property of mankind in its earliest stages of development, branched off the mental life of each group and tribe, not discarding the old, but adding the new under the external compulsion of environment and experience.
Where such externals were alike or nearly so, the progress was parallel; where unlike, it was divergent; analogous in this to well-known doctrines of the biologist.
Such branches were constantly blending in peace or colliding in war, leading to a perpetual interaction of the one growth with the other, engendering a complexity of relation to each other and to the primitive substratum. But the ethnic character, once crystallised, remained as ingrained as the national life or the bodily stigmata. It compelled the members as a mass to look at life and its aims through certain lights, to comprehend the world under certain forms, to move to a measure, and dance to a tune.