EVOLUTION OF SOCIAL STRUCTURES 591
by which the systems are maintained. This is, in fact, the prin- ciple that underlies all genetic structures; but in other depart- ments there are many other elements to be considered which complicate the process. The principle may then be stated in its most general form as the interaction of antagonistic forces. In astronomy these are reduced to the two classes, the centrifugal and centripetal ; but in other departments there are many antago- nistic forces, which need not directly oppose one another, but which modify and restrain one another in a great variety of ways. Any one of these forces considered by itself alone is in the nature of a centrifugal force. In astronomy it is well known that if the centrifugal forces were to operate alone, the systems would be immediately destroyed. This would be equally true of any other system and of all natural structures. Any force considered in and by itself is destructive, and no single force could by any possibility construct a system. All systems and all structures are the result of the interaction of a plurality of forces checking and restraining one another. A single unopposed force can produce only motion of translation. A plurality of interacting forces holds the materials acted upon within a limited area, and while no matter or force can be destroyed, the paths are shortened and converted from straight lines into curves and circles, and the bodies impinged are made to revolve rapidly in limited circuits and vortices, and to arrange themselves into orderly systems with intense internal activities. This is the fundamental condition of all organization, and natural systems or genetic structures are organized mechanisms. If we apply it to the bodies or substances which make up the physical world, we see that the intensive internal activities which they thus acquire constitute what we call their properties, and the differences in the properties that different substances possess are simply the different activities displayed by their molecular components due to the differences in their organization. \Fhis doubtless applies to chemical elements as well as to inorganic or organic compounds, and many chem- ists regard even an atom as a system somewhat analogous to a solar system.
In the organic world the process of organization, due to sue-
