door stood open for all sorts of depravation to creep in. Against this vulgar Arabic the philologists waged unrelenting war, and it was mainly through their exertions that the classical idiom triumphed over the dangers to which it was exposed. Although the language of the pagan Bedouins did not survive intact--or survived, at any rate, only in the mouths of pedants and poets--it became, in a modified form, the universal medium of expression among the upper classes of Muḥammadan society. During the early Middle Ages it was spoken and written by all cultivated Moslems, of whatever nationality they might be, from the Indus to the Atlantic; it was the language of the Court and the Church, of Law and Commerce, of Diplomacy and Literature and Science. When the Mongol invasion in the thirteenth century swept away the ‘Abbásid Caliphate, and therewith the last vestige of political unity in Islam, classical Arabic ceased to be the κοινή or 'common dialect' of the Moslem world, and was supplanted in Arabia, Syria, Egypt, and other Arabic-speaking countries by a vulgar colloquial idiom. In these countries, however, it is still the language of business, literature, and education, and we are told on high authority that even now it "is undergoing a renaissance, and there is every likelihood of its again becoming a great literary vehicle."[14] And if, for those Moslems who are not Arabs, it occupies relatively much the same position as Latin and Greek in modern European culture, we must not forget that the Koran, its most renowned masterpiece, is learned by every Moslem when he first goes to school, is repeated in his daily prayers, and influences the whole course of his life to an extent which the ordinary Christian can hardly realise. [Sidenote: The Nabaṭæans.]