territory a variety of races--Negroes,
Hamites, Semites, Iranians, Indo-Aryans, and a long list of Mongoloid
tribes. Here is a psychological effect of environment. The dry, pure air
stimulates the faculties of the desert-dweller, but the featureless,
monotonous surroundings furnish them with little to work upon. The mind,
finding scant material for sustained logical deduction, falls back upon
contemplation. Intellectual activity is therefore restricted, narrow,
unproductive; while the imagination is unfettered but also unfed. First
and last, these shepherd folk receive from the immense monotony of their
environment the impression of unity.[1182] Therefore all of them, upon
outgrowing their primitive fetish and nature worship, gravitate
inevitably into monotheism. Their religion is in accord with their whole
mental make-up; it is a growth, a natural efflorescence. Therefore it
is strong. Its tenets form the warp of all their intellectual fabrics,
permeate their meager science and philosophy, animate their more
glorious poetry. It has moreover the fanaticism and intolerance
characterizing men of few ideas and restricted outlook upon life.
Therewith is bound up a spirit of propaganda. The victories of the Jews
in Palestine, Syria and Philistia were the victories of Jehovah; the
conquests of Saladin were the conquests of Allah; and the domain of the
Caliphate was the dominion of Islam.

[Illustration: DISTRIBUTION OF RELIGIONS IN THE OLD WORLD (World map
showing distribution of Christians, Mohammedans, Brahmans, Buddhists,
and Heathen).]

[Sidenote: Fanaticism as a force in nomad expansion.]

The desert everywhere, sooner or later, drives out its brood, ejects its
people and their ideas, like those exploding seed-pods which at a touch
cast their seed abroad. The religious fanaticism of the shepherd tribes
gives that touch; herein lies its historical importance. Mohammedism,
fierce and militant, conduced to those upheavals of migration and
conquest which since the seventh century have so often transformed the
political geography of the Old World. The vast empire of the Caliphate,
from its starting point in Arabia, spread in eighty years from the Oxus
River to the Atlantic Ocean.[1183] The rapid rise and spread between 1745
and 1803 of the Wahaby clan and sect, the Puritans of Islam, which
resulted for a time in their political and religious domination of much
of Arabia from their home in the Nejd, recalls the stormy conqu