Mohammedanized — suspicious and scornful of Christian institutions and ideas. The loss of Syria and Egypt combined with the mortal danger from the Saracens intensified the peculiar religious patriotism of the Eastern Empire. This led in turn to a series of quarrels between the popes and the patriarchs of Constantinople. After many schisms, a final break came in 1054 when the Roman Catholic and Greek Orthodox Churches solemnly excommunicated each other. The religious break was merely a symptom of the growing estrangement between East and West. The inhabitants of the Byzantine Empire felt immeasurably superior to the barbarous peoples of the West and dealt with them only for reasons of political and economic convenience. The Westerners viewed the East with suspicion and resentment. The political bond between the three areas had vanished completely; economic contacts were reduced to a minimum, and the cultural patterns which sometimes spread from one region to another were neither numerous nor strong enough to create a common civilization. The Arab Empire, the Byzantine remnant of the Roman Empire, and Western Europe each worked out its own system of institutions and beliefs.
In this shattering of Mediterranean unity it was Western Europe which had the most to lose. The Mohammedans had inherited much of the learning of the Greeks, and to this they added significant material from Persia and India. On these extensive foundations they were able to build a great structure of philosophical and scientific thought which made them leaders in these fields for centuries. They occupied the key position on the ancient trade-route between East and West and made the most of their opportunity by building up an active commerce and thriving industries. Even when, in the ninth century, the Arab Empire broke up into smaller states, Mohammedan civilization retained its essential unity and ideas and goods moved easily from India to Spain. At a time when the largest Western towns were mere fortified villages, when the most learned men of the West were painfully studying commentaries and encyclopedias, the Mohammedans had great