With the same astonishing energy they {69} created centres of culture from Baghdad to Cordova. Through Syriac versions of Aristotle's works Arabian teachers carried Greek philosophy into Western Europe when the light of ancient learning had grown dim. The contact with new thought stimulated theological discussion, and the Moslem had to justify himself against the Christian, the Zoroastrian, the Manichæan and the Buddhist. Above the simple ritual demands of the prophet, the recital of the creed--"There is no god but God (Allah), Mohammed is the apostle of God"--the observance of prayer five times daily, the annual fast in the month of Ramadhān, the bestowal of alms, and the pilgrimage to Mecca, arose the debates of the schools and the divisions of sects. The nature of the divine attributes, and their relation to the being or essence of the Deity, the problems of predestination and free will, of reason and revelation, excited eager interest. Beside the Koran vast numbers of traditions concerning religious life and practice were gradually put in circulation, and in the third century after Mohammed's death they were reduced to writing in six great collections. To these sources of truth and rules of conduct the jurists and theologians added two others: agreement or universal consent, where beliefs and practices are generally received though not specially sanctioned by the Koran or tradition; and analogy, by which a doctrine or usage may be accepted as valid because {70} of its resemblance to something legitimated by revelation. Like the higher religions of India, like Judaism in its long and chequered career whether in Palestine or in the Dispersion, like the "universal religions" of Buddhism and Christianity, Mohammedanism has known how to accommodate itself to very different levels of culture. In the Arabian deserts much of the earlier animism still remains. It is not rudely expelled either at the present day as Islam advances through Africa. Other impulses have worked in different directions. There are religious orders and mendicant ascetics. There are mystical schools of refined spirituality, to which the influences of Neo-platonism, of Christianity, and Buddhism, have all contributed. Sūfiism (as this type of thought is called) was fed from various sources, and has assumed different forms in different countries, but its best-known literary products came from the great poets of Persia.