59 THE AMERICAN JOURNAL OF SOCIOLOGY
human method of constructing is an artificial method. This con- sists in first forming in the mind an ideal of the finished product, and then arranging the materials in such wise that they will realize that product. The end is seen from the beginning. It is a final or teleological method. Nature also constructs, but the method of nature is just the opposite of that of man. There is no foresight, and the materials are added in small increments until the structure is completed. The method of nature is a differential or genetic method. All natural structures are of this class, and social structures are natural structures.
But natural structures are not so simple as might appear from this statement. They do not consist in the mere mechanical apposition of the raw materials brought into material contact. This would produce only a mass, a heap, a mixture ; it would not produce a structure. A structure implies a certain orderly arrangement and harmonious adjustment of the materials, an adaptation of the parts and their subordination to the whole. How does blind nature accomplish this? It does it according to a universal principle, and it would be impossible to convey any clear conception of the process of social structure without first setting forth, at least briefly, the character of this principle.
It is not only in human society that natural or genetic struc- tures are formed. The organic world affords perhaps the most striking example of the process, and all organisms not only consist of such structures, but are themselves organic structures. Every other department of nature furnishes examples, but there is one other in which the process is so simple that it is easily grasped by the average mind. This is that of astronomy. Each one of the heavenly bodies is a natural structure formed by the raw materials and blind forces of nature, and yet the heavenly bodies are highly symmetrical and perfectly ordered structures. The solar system and all other star systems are also such struc- tures, in which there is perfect adjustment of parts and subordina- tion of the parts to the whole.
This last example will serve a good purpose in explaining the principle, because we are already familiar with the facts of centrifugal and centripetal forces which constitute the principle
