A further feature of this emerging European civilization was a distinctive intellectual tension between the claims of human reason and those of faith. Christianity had developed in a world suffused with Greek rationalism. Some early Christian thinkers sought to maintain a clear separation between the new religion and the ideas of Plato and Aristotle. “What indeed has Athens to do with Jerusalem?” asked Tertullian (150–225 C.E.), an early church leader from North Africa. More common, however, was the notion that Greek philosophy could serve as a “handmaiden” to faith, more fully disclosing the truths of Christianity. In the reduced circumstances of Western Europe after the collapse of the Roman Empire, the Church had little direct access to the writings of the Greeks, although some Latin translations and commentaries provided a continuing link to the world of classical thought.

But intellectual life in Europe changed dramatically in the several centuries after 1000, amid a rising population, a quickening commercial life, emerging towns and cities, and the Church’s growing independence from royal or noble authorities. Moreover, the West was developing a legal system that provided a measure of independence for a variety of institutions—towns and cities, guilds, professional associations, and especially universities. An outgrowth of earlier cathedral schools, these European universities—in Paris, Bologna, Oxford, Cambridge, Salamanca—became “zones of intellectual autonomy” in which scholars could pursue their studies with some freedom from the dictates of religious or political authorities, although that freedom was never complete and was frequently contested.31

This was the setting in which European Christian thinkers, a small group of literate churchmen, began to emphasize, quite self-consciously, the ability of human reason to penetrate divine mysteries and to grasp the operation of the natural order. An early indication of this new emphasis occurred in the late eleventh century when students in a monastic school in France asked their teacher, Anselm, to provide them a proof for the existence of God based solely on reason, without using the Bible or other sources of divine revelation.

The new interest in rational thought was applied first and foremost to theology, the “queen of the sciences” to European thinkers. Here was an effort to provide a rational foundation for faith, not to replace faith or to rebel against it. Logic, philosophy, and rationality would operate in service to Christ. Of course, some opposed this new emphasis on human reason. Bernard of Clairvaux, a twelfth-century French abbot, declared, “Faith believes. It does not dispute.”32 His contemporary and intellectual opponent, the French scholar William of Conches, lashed out: “You poor fools. God can make a cow out of a tree, but has he ever done so? Therefore show some reason why a thing is so or cease to hold that it is so.”33

European intellectuals also applied their newly discovered confidence in human reason to law, medicine, and the world of nature, exploring optics, magnetism, astronomy, and alchemy. Slowly and never completely, the scientific study of nature, known as “natural philosophy,” began to separate itself from theology. In European universities, natural philosophy was studied in the faculty of arts, which was separate from the faculty of theology, although many scholars contributed to both fields.

This mounting enthusiasm for rational inquiry stimulated European scholars to seek out original Greek texts, particularly those of Aristotle. They found them in the Greek-speaking world of Byzantium and in the Islamic world, where they had long ago been translated into Arabic. In the twelfth and thirteenth centuries, an explosion of translations from Greek and Arabic into Latin, much of it undertaken in Spain, gave European scholars direct access to the works of ancient Greeks and to the remarkable results of Arab scholarship in astronomy, optics, medicine, pharmacology, and more. Much of this Arab science was now translated into Latin and provided a boost to Europe’s changing intellectual life, centered in the new universities. One of these translators, Adelard of Bath (1080–1142), remarked that he had learned, “under the guidance of reason from Arabic teachers,” not to trust established authority.34

It was the works of the prolific Aristotle, with his logical approach and “scientific temperament,” that made the deepest impression. His writings became the basis for university education and largely dominated the thought of Western Europe in the five centuries after 1200. In the work of the thirteenth-century theologian Thomas Aquinas, Aristotle’s ideas were thoroughly integrated into a logical and systematic presentation of Christian doctrine. In this growing emphasis on human rationality, at least partially separate from divine revelation, lay one of the foundations of the later Scientific Revolution and the secularization of European intellectual life.

Surprisingly, nothing comparable occurred in the Byzantine Empire, where knowledge of the Greek language was widespread and access to Greek texts was easy. Although Byzantine scholars kept the classical tradition alive, their primary interest lay in the humanities (literature, philosophy, history) and theology rather than in the natural sciences or medicine. Furthermore, both state and church had serious reservations about Greek learning. In 529, the emperor Justinian closed Plato’s Academy in Athens, claiming that it was an outpost of paganism. Its scholars dispersed into lands that soon became Islamic, carrying Greek learning into the Islamic world. Church authorities as well were suspicious of Greek thought, sometimes persecuting scholars who were too enamored with the ancients. Even those who did study the Greek writers did so in a conservative spirit, concerned to preserve and transmit the classical heritage rather than using it as a springboard for creating new knowledge. “The great men of the past,” declared the fourteenth-century Byzantine scholar and statesman Theodore Metochites, “have said everything so perfectly that they have left nothing for us to say.”35

In the Islamic world, Greek thought was embraced “with far more enthusiasm and creativity” than in Byzantium.36 A massive translation project in the ninth and tenth centuries made Aristotle and many other Greek writers available in Arabic. That work contributed to a flowering of Arab scholarship, especially in the sciences and natural philosophy, between roughly 800 and 1200 (see Chapter 9), but it also stimulated a debate about faith and reason among Muslim thinkers, many of whom greatly admired Greek philosophical, scientific, and medical texts. As in the Christian world, the issue was whether secular Greek thought was an aid or a threat to the faith. Western European church authorities after the thirteenth century had come to regard natural philosophy as a wholly legitimate enterprise and had thoroughly incorporated Aristotle into university education, but learned opinion in the Islamic world swung the other way. Though never completely disappearing from Islamic scholarship, the ideas of Plato and Aristotle receded after the thirteenth century in favor of teachings that drew more directly from the Quran or from mystical experience. Nor was natural philosophy a central concern of Islamic higher education as it was in the West. The integration of political and religious life in the Islamic world, as in Byzantium, contrasted with their separation in the West, where there was more space for the independent pursuit of scientific subjects.