together, will, in the rude state of knowledge in which reliance for
subsistence must be principally upon the spontaneous offerings of
nature, very largely depend upon climate, soil, and physical
conformation. Where much animal food and warm clothing are required;
where the earth seems poor and niggard; where the exuberant life of
tropical forests mocks barbarous man's puny efforts to control; where
mountains, deserts, or arms of the sea separate and isolate men;
association, and the power of improvement which it evolves, can at first
go but a little way. But on the rich plains of warm climates, where
human existence can be maintained with a smaller expenditure of force,
and from a much smaller area, men can keep closer together, and the
mental power which can at first be devoted to improvement is much
greater. Hence civilization naturally first arises in the great valleys
and table-lands where we find its earliest monuments.

But these diversities in natural conditions, not merely thus directly
produce diversities in social development, but, by producing diversities
in social development, bring out in man himself an obstacle, or rather
an active counterforce, to improvement. As families and tribes are
separated from each other, the social feeling ceases to operate between
them, and differences arise in language, custom, tradition, religion--in
short, in the whole social web which each community, however small or
large, constantly spins. With these differences, prejudices grow,
animosities spring up, contact easily produces quarrels, aggression
begets aggression, and wrong kindles revenge.[45] And so between these
separate social aggregates arises the feeling of Ishmael and the spirit
of Cain, warfare becomes the chronic and seemingly natural relation of
societies to each other, and the powers of men are expended in attack or
defense, in mutual slaughter and mutual destruction of wealth, or in
warlike preparations. How long this hostility persists, the protective