An equal amount of energy was devoted to achieving a scientific understanding of nature, but it is essential to understand to what use medieval thinkers put this kind of knowledge. As the fertility of the technology shows, medieval Europeans had no deep prejudices against utilitarian knowledge. But the areas in which scientific knowledge could find useful expression were few. Instead, science was viewed chiefly as a means of understanding God’s creation and, thereby, the Godhead itself. The best example of this attitude is found in the medieval study of optics. Light, as Genesis makes clear, was among the first creations of God. The 12th–13th-century cleric-scholar Robert Grosseteste saw in light the first creative impulse. As light spread, it created both space and matter, and, in its reflection from the outermost circle of the cosmos, it gradually solidified into the heavenly spheres. To understand the laws of the propagation of light was to understand, in some slight way, the nature of the creation.
In the course of studying light, particular problems were isolated and attacked. What, for example, is the rainbow? It is impossible to get close enough to a rainbow to see clearly what is going on, for as the observer moves, so too does the rainbow. It does seem to depend upon the presence of raindrops, so medieval investigators sought to bring the rainbow down from the skies into their studies. Insight into the nature of the rainbow could be achieved by simulating the conditions under which rainbows occur. For raindrops the investigators substituted hollow glass balls filled with water, so that the rainbow could be studied at leisure. Valid conclusions about rainbows could then be drawn by assuming the validity of the analogy between raindrops and water-filled globes. This involved the implicit assumptions that nature was simple (i.e., governed by a few general laws) and that similar effects had similar causes. Such a nature was what could be expected of a rational, benevolent deity. Hence, the assumption could be persuasively adopted.
Medieval philosophers were not content, as the above example shows, to repeat what the ancients had said. They subjected ancient texts to close critical scrutiny. Usually, the intensity of the criticism was directly proportional to the theological significance of the problem involved. Such was the case with motion. Medieval philosophers examined all aspects of motion with great care, for the nature of motion had important theological implications. Thomas Aquinas used Aristotle’s dictum, that everything that moves is moved by something else, to show that God must exist, for otherwise the existence of any motion would imply an infinite regression of prior causal motions.
It should be clear that there was no conscious conflict between science and religion in the Middle Ages. As Aquinas pointed out, God was the author of both the book of Scripture and the book of nature. The guide to nature was reason, the faculty that was the image of God in which humankind was made. Scripture was direct revelation, although it needed interpretation, for there were passages that were obscure or difficult. The two books, having the same author, could not contradict each other. For the short term, science and revelation marched hand in hand. Aquinas carefully wove knowledge of nature into his theology, as in his proof from motion of the existence of God. But if his scientific concepts of motion should ever be challenged, there would necessarily be a theological challenge as well. By working science into the very fabric of his theology, he virtually guaranteed that someday there would be conflict. Theologians would side with theology and scientists with science, to create a breach that neither particularly desired.
The glory of medieval science was its integration of science, philosophy, and theology into a magnificent and comprehensible whole. It can be best contemplated in the greatest of all medieval poems, Dante’s Divine Comedy. Here was an essentially Aristotelian cosmos, finite and easily understood, over which God, his Son, and his saints reigned. Humanity and Earth occupied the centre, as befitted their centrality in God’s plan. The nine circles of hell were populated by humans whose exercise of their free will had led to their damnation. Purgatory contained lesser sinners still capable of salvation. The heavenly spheres were populated by the saved and the saintly. The natural hierarchy gave way to the spiritual hierarchy as one ascended toward the throne of God. Such a hierarchy was reflected in the social and political institutions of medieval Europe, and God, the supreme monarch, ruled his creation with justice and love. All fit together in a grand cosmic scheme, one not to be abandoned lightly. The rise of modern science The authority of phenomena
Even as Dante was writing his great work, deep forces were threatening the unitary cosmos he celebrated. The pace of technological innovation began to quicken. Particularly in Italy, the political demands of the time gave new importance to technology, and a new profession emerged, that of civil and military engineer. These people faced practical problems that demanded practical solutions. Leonardo da Vinci is certainly the most famous of them, though he was much more as well. A painter of genius, he closely studied human anatomy in order to give verisimilitude to his paintings. As a sculptor, he mastered the difficult techniques of casting metal. As a producer-director of the form of Renaissance dramatic production called the masque, he devised complicated machinery to create special effects. But it was as a military engineer that he observed the path of a mortar bomb being lobbed over a city wall and insisted that the projectile did not follow two straight lines—a slanted ascent followed by a vertical drop—as Aristotle had said it must. Leonardo and his colleagues needed to know nature truly; no amount of book learning could substitute for actual experience, nor could books impose their authority upon phenomena. What Aristotle and his commentators asserted as philosophical necessity often did not gibe with what could be seen with one’s own eyes. The hold of ancient philosophy was too strong to be broken lightly, but a healthy skepticism began to emerge.
The first really serious blow to the traditional acceptance of ancient authorities was the discovery of the New World at the end of the 15th century. Ptolemy, the great astronomer and geographer, had insisted that only the three continents of Europe, Africa, and Asia could exist, and Christian scholars from St. Augustine on had accepted it, for otherwise men would have to walk upside down at the antipodes. But Ptolemy, St. Augustine, and a host of other authorities were wrong. The dramatic expansion of the known world also served to stimulate the study of mathematics, for wealth and fame awaited those who could turn navigation into a real and trustworthy science.
In large part the Renaissance was a time of feverish intellectual activity devoted to the complete recovery of the ancient heritage. To the Aristotelian texts that had been the foundation of medieval thought were added translations of Plato, with his vision of mathematical harmonies, of Galen, with his experiments in physiology and anatomy, and, perhaps most important of all, of Archimedes, who showed how theoretical physics could be done outside the traditional philosophical framework. The results were subversive.
The search for antiquity turned up a peculiar bundle of manuscripts that added a decisive impulse to the direction in which Renaissance science was moving. These manuscripts were taken to have been written by or to report almost at first hand the activities of the legendary priest, prophet, and sage Hermes Trismegistos. Hermes was supposedly a contemporary of Moses, and the Hermetic writings contained an alternative story of creation that gave humans a far more prominent role than the traditional account. God had made humankind fully in his image: a creator, not just a rational animal. Humans could imitate God by creating. To do so, they must learn nature’s secrets, and this could be done only by forcing nature to yield them through the tortures of fire, distillation, and other alchemical manipulations. The reward for success would be eternal life and youth, as well as freedom from want and disease. It was a heady vision, and it gave rise to the notion that, through science and technology, humankind could bend nature to its wishes. This is essentially the modern view of science, and it should be emphasized that it occurs only in Western civilization. It is probably this attitude that permitted the West to surpass the East, after centuries of inferiority, in the exploitation of the physical world.