Only in the Roman Empire and in Spain under Arab domination has culture been a potent factor. Under the Arab, the standard attained was wholly admirable; to Spain flocked the greatest scientists, thinkers, astronomers, and mathematicians of the world, and side by side there flourished a spirit of sweet human tolerance and a sense of purist chivalry. Then with the advent of Christianity, came the barbarians.

Secret Conversations, 1941-1944 (ed. 1953)