human inertia, ineptitude, and the human urges to build,
decorate and destroy.

Variety in human culture is caused by the variety in the human natural
environment, the human social environment and in man himself.

Natural advantages exist and vary from place to place. There are fertile
valleys; there are also mountains and deserts. There are a few fine
harbors, but for the most part landings are difficult and dangerous.
Certain islands have become the bases of civilizations, but this is true
of only a very small number of many existing islands.

Civilizations have flourished in certain climatic zones and not
elsewhere. At one historical period civilizations were established in
the tropics and semi-tropics. In the present period they are located
chiefly in temperate climatic belts.

Another source of differences between civilizations is the variation and
the adaptability of certain peoples to the peculiar conditions out of
which civilization grows.

Still another explanation of the presence or absence of civilization in
particular times and places is the "great man" theory of history. All
human communities, pre-civilized and civilized, have had gifted leaders
whose thoughts and actions have brought about social changes. These
"greats" were the divinely, ideologically or sociologically inspired.
Divine inspiration or revelation led to the founding of religious
faiths. Ideological and sociological inspiration resulted in domestic
cultural changes and the extension of economic, cultural and ideological
activities into foreign lands, thus pushing the frontiers of nations,
empires, and civilizations farther from the chief wealth-power centers.

Thomas Carlyle wrote that history is the lengthened shadows of a few
great men. Arnold Toynbee concluded from his _Study of History_ that
religion has been a prime motive force in the building and preservation
of civilizations.

Technology has been a motive force of hard-to-define importance in
revitalizing, changing, expanding and perpetuating civilizations.
Increased productivity, expressing itself as increases in income,
accumulated wealth and various forms of capital investment, have
provided the economic basis for population growth and the more effective
exploitation of natural resources and labor power, advances in the means
for transportation and communication, accounting, planning management
and "defense."

Among the social motive forces responsible for the developmen