Modern language, science and culture owes much to the Muslim empire of the early Middle Ages.
'We should not be ashamed to acknowledge truth from whatever source it comes to us, even if it is brought to us by former generations and foreign peoples.' The philosopher Al-Kindi, who wrote those words in 9th century Baghdad, understood better than most how much human history has been shaped by the interaction of different cultures. He was one of the thousands of Arab scholars employed to translate, analyse and develop Greek learning by the Abbasid caliphs, rulers of the great Muslim empire of the 8th to the 13th centuries.
The translation of hundreds of works of philosophy, science, music, mathematics and medicine had a lasting influence on the Arabic language, and Arab and Muslim culture. The translators did not simply transmit the ideas of others unchanged, but rather reshaped Greek sciences to fit the needs of a different society. Arab doctors developed and refined the medicine of the Ancient Greeks while Arab philosophers applied Aristotle's principles to theology and law. Two centuries after Al-Kindi it would be European scholars who were flocking to study Arabic in order to transmit both Greek and Arab learning to a new audience in the cultural backwaters of England, France and Italy.
Robert of Chester was one such scholar. He travelled from England to Toledo in Spain to learn Arabic, and in 1145 completed a translation of Abu-Ja'far Muhammad Ibn Musa al-Khwarizimi's treatise on calculation. Al-Khwarizimi's work, which was already two centuries old by the time Robert of Chester read it, gave us the words 'algebra' - from the Arabic 'al-jabr' - and 'algorithm' - a corrupted version of the author's name. It also popularised the use of Indian numerals 1, 2, 3 in place of the cumbersome Latin system used in Europe at the time. Al-Khwarizimi also worked on linear and quadratic equations; the use of the letter 'x' to denote the unknown in algebra also developed out of the Arabic word shay, or 'thing', which was rendered 'xay' in Spanish.
The work by Arab mathematicians on algebra and number theory also stimulated discoveries in other areas such as geometry, trigonometry and astronomy. Arab scholars did more than translate and transmit - they also developed and refined the ideas of the Greeks. Omar Khayyam, known chiefly in Europe as a poet, combined trigonometry and approximation theory to solve algebraic equations using geometry. Astronomy also took a leap forward through the combination of Greek and Arab learning. Arab craftsmen produced complex astronomical instruments, astrolabes, which helped them plot the positions of the stars and tell the time of day.
Muslim Spain, or Al-Andalus, in particular played a crucial role in the cross-fertilisation of Arab and European culture. Conquered by Muslim armies in the first century of Islam, Spain became an extraordinary cultural melting-pot. Muslims, Jews and Christians, Arabs, Berbers and indigenous Spaniards all played a part in developing poetry, philosophy and music. Maimonides, the great Jewish philosopher and doctor who was born in Cordoba in 1135, was one such figure. His most important work, Guide of the Perplexed, was influenced by the writings of the Muslim scholar Al-Farabi on Plato and Aristotle. Cordoba was also the birthplace of Maimonides' contemporary, the philosopher Ibn Rushd - better known as Averroes in Europe - the foremost commentator on Aristotle of his day.
One of the glories of Al-Andalus was its architecture, described by Titus Burckhardt as an 'alchemy of light'. Here he describes the great palace of the Alhambra in Granada: 'The Court of the Lions in particular sets the example of stone transformed into a vibration of light; the lambrequins of the arcades, the friezes in muqarnas, the delicacy of the columns which seem to defy gravity, the scintillation of the roofs in green tile work and even the water jets of the fountain, all contribute to this impression.'
Spain and Sicily also saw the transmission of paper making to Europe from the Middle East. Arab craftsmen learnt this new technology from China in the 8th century and brought it with them to Spain, from where it reached the rest of Europe by the 12th century. Our reams of paper today still bear the traces of this long journey - 'ream' comes from Old French 'rayme' and Spanish 'resma', a word directly borrowed from the Arabic 'rizmah', meaning a bale or a bundle. Paper making had already played a significant role in reshaping Arab society before it reached Europe. As early as the 9th century, the court bureaucracy of the Abbasid caliphs relied on paper documents to record government transactions, rather than parchment. The Stationers' Market in Baghdad was home to more than 100 paper and booksellers at the same period. When the Mongols sacked Baghdad in 1258, it was said that the Tigris river ran black with the ink from the city's ruined libraries. At the same date, it is unlikely that the books of London would have discoloured more than a puddle or two.
Spain did not only form a meeting point between the Muslim and Christian states of the early Middle Ages, it was also a contested border zone, scarred by conflict as well as shaped by cultural exchange. Robert of Chester translated the books captured as war booty when Toledo fell to the Christian King Alphonso VI in 1085. War bred intolerance and cruelty on all sides: Maimonides fled from Cordoba to Cairo after the city was taken by the Muslim Almohad dynasty, who launched a series of attacks on Jews and Christians. By the 14th and 15th centuries all that remained of Al-Andalus was a tiny enclave on the southern coast. The last great city of Al-Andalus, Granada, fell to Christian forces in 1492. Many of its Muslim and Jewish inhabitants fled rather than face the horrors of the Inquisition, following the route taken by earlier refugees to North Africa. Abd al-Rahman Ibn Khaldun, one of the great pioneers of sociology, came from just such a family - refugees from Seville, who migrated to Tunisia in the early 14th century. His Muqaddimah (The Introduction, or Prolegomena in Latin) was one of the first attempts to provide a theory to explain the pattern of events in history, as opposed to merely listing the deeds of the rich and powerful.
Thousands of miles from Spain, war and conquest also played a part in the transfer of ideas from east to west. The crusades - celebrated in European history as a heroic endeavour by pious Christians to free Jerusalem from Muslim rule - were remembered by Arab historians as a period of destruction and terror. The Crusaders' brutal occupation of parts of what is today Lebanon and Palestine did, however, speed up the movement of new technologies. Soldiers returning from the Crusades brought back new tools such as the wheelbarrow, and popularised the use of windmills.
The knowledge and skill of Arab doctors, who had maintained Greek medicine as a living tradition when most Europeans had forgotten it, was also transmitted to Europe around this time. The Persian doctor and statesman Ibn Sina - also known as Avicenna - was one of the most influential writers on medicine of his time. Ibn Sina's Qanun fi l-Tibb (Canon of Medicine) served as a basis for more than seven centuries of medical teaching and practice. It covered topics as diverse as the treatment of diarrhoea, pharmacology of herbs, fevers, tumours and pathology. Generations of doctors across the Arab world and Europe learnt the principles of Ibn Sina's teachings as a mnemonic: the poem was translated into Latin several times between the 13th and 17th centuries as the Cantica Avicennae.
It was through the work of Muslim philosophers such as Ibn Rushd and Ibn Sina that practically all of Aristotle's writings were rediscovered in Europe. The collapse of the Roman Empire in the west meant more than the destruction of a system of government, it also saw huge cultural losses as towns shrank, libraries were destroyed and literacy declined. Aristotle's works were only preserved in the eastern part of the Roman Empire, which had its capital in Byzantium, and from there travelled to Baghdad to be translated by Al-Kindi and his contemporaries.
The value of Aristotle's work to European scholars of the 12th century was not the result of some abstract qualities embodied in the text, however. The ideas had to connect with the material and social realities of the age. The translation movement in 9th century Baghdad was produced by the needs of the rulers of a powerful empire. The trading networks which played such a crucial role in the development of the Muslim empire were able to carry new ideas to far-flung corners of the world. Likewise in Europe in the 12th century Aristotle's ideas, as developed by Arab writers, were not simply translated by chance. They were taken up by a new class of lay teachers in Europe who wanted and needed a different kind of knowledge to the church learning of the clergy. This new knowledge, which relied on reason rather than on rote learning and deference, was one of the seeds which would germinate into the Renaissance.