The last is the salient circumstance. In any society, the special cultivation of serious literature and the arts and sciences depends on one or more of three conditions--(_a_) the existence of a cultured class living on unearned incomes, as in ancient Athens, middle Rome, and modern England and France; (_b_) public expenditure on art and culture, as in ancient Athens, Renaissance Italy and modern France, and in the German university system _par excellence_; or (_c_) the personal concern of princes and other patrons to encourage ability. In the nature of the case it was mainly on this last and most precarious stimulus that Saracen culture depended. Taking it at its zenith, under such rulers as Haroun Alraschid and El-Mamoun at Bagdad, and Abderrahman III and Hakam II of Cordova, we find its advance always more or less dependent on the bounty of the caliph; and even if, like Abderrahman and his son Hakam, he founded all manner of public and free schools, it depended on the bias of his successors rather than on public opinion or municipal custom whether the movement should continue. Abderrahman's achievement, seen even through Christian eyes, was so manifold as to constitute him one of the great rulers of all history; but the task of making Moorish civilisation permanent was one which no series of such statesmen could have compassed. The natural course of progress would have been through stable monarchy to constitutionalism. But Christian barbarism, with its perpetual assault, kept the Saracens forever at the stage of active militarism, which is the negation of constitutionalism; and their very refinement was a political danger, no less than their dynastic strifes.