He first gathers his facts, from the best sources at his command, with the closest sifting he can give them, so as to exclude errors of observation or intentional bias. From the facts he aims to discover on the above lines what are or were the regular characteristics of the people or peoples he is studying. The ethnic differences so revealed are to him what organic variations are to the biologist and morphologist; they indicate evolution or retrogression, and show an advance toward higher forms and wider powers, or toward increasing feebleness and decay. To understand them they must be studied in connection and causation. Hence, the method of the ethnologist becomes that which in the natural sciences is called the "developmental" method. It may be defined as the historic method where history is lacking. The biologist explains the present structure of an organ by tracing it back to simpler forms in lower animals until he reaches the germ from which it began. The ethnologist pursues the same course. He selects, let us say, a peculiar institution, such as caste, and when he loses the traces of its origin through failure of written records, he seeks for them in the survivals of unwritten folk-lore, or in similar forms in primitive conditions of culture. Here is where Archaeology renders him most efficient aid. By means of it he has been able to follow the trail of most of the arts and institutions of life back to a period when they were so simple and uncomplicated that they are quite transparent and intelligible. Later changes are to be analyzed and explained by the same procedure.[12-1] This is the whole of the ethnologic method. It is open and easy when the facts are in our possession. There are no secret springs, no occult forces, in the historic development of culture. Whatever seems hidden or mysterious, is so only because our knowledge of the facts is imperfect. No magic and no miracle has aided man in his long conflict with the material forces around him. No ghost has come from the grave, no God from on high, to help him in the bitter struggle. What he has won is his own by the right of conquest, and he can apply to himself the words of the poet: "Hast du nicht alles selbst vollendet, Heilig gluehend Herz?" (_Goethe_). Freed from fear we can now breathe easily, for we know that no _Deus ex machina_ meddles with those serene and mighty forces whose adamantine grasp encloses all the phenomena of nature and of life. The ethnologist, however, has not completed his task when he has defined an _ethnos_, and explained its traits by following them to their sources. He has merely prepared himself for a more delicate and difficult part of his undertaking.