It is clear that every civilization undergoes a process of historical change. We can see that a civilization comes into existence, passes through a long experience, and eventually goes out of existence.

To know is not too demanding: it merely requires memory and time. But to understand is quite a different matter: it requires intellectual ability and training, a self conscious awareness of what one is doing, experience in techniques of analysis and synthesis, and above all, perspective.

A civilization is complicated, in the first place, because it is dynamic; that is, it is constantly changing in the passage of time, until it has perished.

After years of work in both areas of study, I concluded that the social sciences were different, in many important ways, from the natural sciences, but that the same scientific methods were applicable in both areas, and, indeed, that no very useful work could be done in either area except by scientific methods.

A community is made up of intimate relationships among diversified types of individuals--a kinship group, a local group, a neighborhood, a village, a large family.

When goods are exchanged between countries, they must be paid for by commodities or gold. They cannot be paid for by the notes, certificates, and checks of the purchaser's country, since these are of value only in the country of issue.

A state is not the same thing as a society, although the Greeks and Romans thought it was. A state is an organization of power on a territorial basis.