Religion and Science in the Middle Ages

Edward Grant. Science, Religion, and Society: An Encyclopedia of History, Culture, and Controversy. Editor: Arri Eisen & Gary Laderman. Volume 1. Armonk, NY: M.E. Sharpe, 2006.

Although it is customary to use the terms religion and science in any discussion about the interrelationships between these two broad subjects during the Middle Ages (c. 500-1500), it would be more accurate to substitute theology andnatural philosophy, reserving science for the exact sciences that were dependent on mathematics: astronomy, optics, and mechanics. To these, the very inexact science of medicine might be added, since it was regarded as an independent discipline from the days of the great Greek physician Hippocrates in the fifth century BCE. If we confined our attention to the relations between religion and the exact sciences and medicine, there would be little to say, largely because there were no significant issues involving these subject areas during the Middle Ages.

With the exception of the exact sciences and medicine, the operations and structure of the rest of the cosmos was studied by natural philosophy, a discipline that was largely derived from the works of the great Greek philosopher and scientist Aristotle in the fourth century BCE. Natural philosophy, as it was understood from the early centuries of Christianity to the end of the Middle Ages, was the study of change and motion in the physical world. Because its domain was the whole of nature, natural philosophy did not, and could not, represent any single science. Instead, it embraced bits and pieces of numerous sciences, such as physics, cosmology, geology, meteorology, biology, and psychology. It also included theories of the origins of the world, whether it had a beginning or always existed; how animate and inanimate bodies are generated and how they are corrupted and come to an end; how and why bodies fall or rise, and what causes them to move from one place to another; how bodies would act under certain imaginary conditions within or beyond our world.

The secular discipline of natural philosophy raised concerns for the Christian church, which at times attempted to eliminate any claims that seemed hostile to the religion. But the efforts to protect Christians were only temporary reactions, eventually replaced by a full acceptance of that important discipline.

Early Christianity and Greek Science

During the early centuries following the birth of Christianity, the Greek church fathers played an instrumental role in shaping Christian attitudes toward pagan learning, especially Greek science and natural philosophy. Because they came from different backgrounds, the Greek church fathers were hardly of one mind. Some were hostile to science, fearing it as a rival to the faith and as potentially subversive. Others, such as Clement of Alexandria (c. 150-215) and his disciple Origen of Alexandria (c. 185-254), were convinced that Christians stood to profit from knowledge of Greek philosophy and science, so long as these subjects were not studied for their own sakes, but only as “handmaidens to theology,” a procedure already advocated early in the first century CE by Philo of Alexandria, or Philo Judaeus, a resident of the Jewish community of Alexandria. The “handmaiden” approach won widespread support within Christianity and triumphed over the rival approach that sought to avoid all contact with Greek science and learning. It was a compromise between the total rejection of pagan learning and its full acceptance. Christians felt free to use Greek philosophy and science to explicate holy scriptures as well as to elucidate problems in other aspects of their lives. To explain Genesis, with its description of the six days of creation, Greek science and natural philosophy were essential, as is evident in the three great commentaries on Genesis by Basil, Ambrose, and Augustine, which were influential throughout the Middle Ages.

During the first six centuries of Christianity, pagan Greeks continued to contribute to the storehouse of Greek science and natural philosophy. Treatises were written that significantly advanced mathematics, astronomy, medicine, and engineering. In the fifth and sixth centuries, commentaries were written on the scientific works of Aristotle that would play an influential role in medieval natural philosophy. The cultural context within which science and natural philosophy functioned, however, was altered when the Roman Empire split into two parts. The eastern part, which became the Byzantine Empire, survived until 1453; the western part fell into serious decline under the impact of barbarian invasions between the fifth and tenth centuries.

The Introduction of Aristotle’s Natural Philosophy

By the eleventh century, a new Europe was emerging that differed greatly from the Roman Empire. There was a great emphasis on agriculture, urbanization, and education. Europeans knew they were impoverished in the sciences and natural philosophy and wished to remedy this deficiency. To do this they had to translate Greek and Arabic works into Latin, a process they eagerly began in the twelfth century and continued to the end of the thirteenth. When the process was completed, translators in Western Europe had translated into Latin most of the great works from Greek and Arabic authors. This literature ranged over the exact sciences, medicine, and especially natural philosophy. In the latter category, the most important works were those of Aristotle (384-322 BCE), probably the greatest philosopher and scientist of the ancient world.

Aristotle’s works on logic and natural philosophy came to dominate intellectual discourse throughout the late Middle Ages to the end of the seventeenth century. The core treatises in his natural philosophy are commonly titled: Physics, On the Heavens, On Generation and Corruption, Meteorology, and On the Soul. His works on logic and metaphysics were also extremely important, as were his treatises on biology, politics, and rhetoric. But Aristotle’s works on natural philosophy proved controversial and, for some, threatening. The hostile reaction to Aristotle’s natural philosophy occurred largely in the thirteenth century, the first century when most of Aristotle’s works were available for study and discussion. Prior to the translations from Greek and Arabic into Latin, Western Europe was largely ignorant of the great works of science and natural philosophy that were long known in the Byzantine Empire and Islam. With the influx of such a large body of translated science, it is appropriate to inquire how Christians responded to a body of literature with which they were unfamiliar, but eagerly sought, even though they were probably aware that lurking in that literature were potential problems for the faith.

Even before the great age of translation, Europe was astir in the twelfth century, when the major source of natural philosophy was Plato’s Timaeus. The better-known natural philosophers of this period—Honorius of Autun, Thierry of Chartres, William of Conches, Adelard of Bath, and others—began to challenge ecclesiastical authority by rejecting causal explanations of natural phenomena that invoked God’s omnipotence or relied on biblical passages. Appeals to divine causation came to be regarded as little more than confessions of ignorance. Many scholars in the twelfth century were convinced that only natural explanations could properly explain natural phenomena. In the dynamic society that emerged in the twelfth century, human reason was given a central role that it had not previously had. William of Conches (c. 1080-1154), for example, exalted reason over ecclesiastical authority when he criticized “modern priests” who “do not want us to inquire into anything that isn’t in the Scriptures, only to believe simply, like peasants.” Although he conceded that it is not lawful to speak against the faith or against the church fathers, William insisted: “in those matters concerning philosophy, if they err in any respect, it is permissible to differ from them. For even though they were greater men than we are, yet they were men.”

With the ready availability of new Latin translations of Aristotle’s natural philosophy in the thirteenth century, reason was given a central role that it had not had before. For the first time in the history of Latin Christendom, an extensive, powerful body of learning, rich in natural knowledge, metaphysics, logic, and reasoned argumentation, was available for study and use as a basic curriculum in the new universities that had come into being by 1200 in Paris, Oxford, and Bologna. Some, if not many, theologians grew alarmed at the prospect of a rival, secular body of knowledge that seemed capable of subverting scripture and the revealed truths of the faith.

The Theological Reaction to Aristotle

Aristotle’s description of the cosmos was, unlike Plato’s, in direct conflict with the Christian account in Genesis of a world created by God. Aristotle assumed an eternal, uncreated world, without beginning or end. He assumed the existence of a God, but one utterly unlike the Christian God. Moreover, Aristotle’s God has no knowledge of the world’s existence. Aristotle’s natural philosophy disagreed with the Christian faith on other serious points, enough to worry the theological authorities in Paris, home of the University of Paris, the most prestigious university in Christendom. They were fearful that Aristotle’s natural philosophy was too popular, especially since it was already being used as the basis for the curriculum in the faculty of arts at the University of Paris, and at other universities.

The first significant reaction came in 1210 when the members of the provincial synod of Sens, which included the bishop of Paris as a member, issued a denunciation of various individuals they viewed as heretics, after which they declared that “Neither the books of Aristotle on natural philosophy nor their commentaries are to be read at Paris in public or secret, and this we forbid under penalty of excommunication.” The prohibition was probably ineffective, as evidenced by the fact that it was essentially repeated in 1215. A milder approach was taken in 1231, when Pope Gregory IX established a three-man committee to “entirely exclude what you shall find there erroneous or likely to give scandal or offense to readers, so that, what are suspect being removed, the rest may be studied without delay and without offense.” Pope Gregory invoked the biblical account of the Hebrews despoiling the Egyptians by taking the gold and silver vessels and leaving those of rusty copper or clay. As far as is known, the committee never submitted a report, and the effort to expurgate Aristotle’s natural philosophy was never carried out.

Presumably, the ban on reading Aristotle’s natural philosophy remained in effect between 1210 and around 1255. During this period, only Aristotle’s ethical and logical works were taught publicly in Paris; his natural philosophy was probably read in private. Whatever the efficacy of the ban, it came to an end no later than 1255, when a list of textbooks in use at the University of Paris included all of Aristotle’s books on natural philosophy. Thus did the scholars of Paris join their Oxford University colleagues, who had always enjoyed the privilege of lecturing and commenting on all the works of Aristotle.

The Thirteen Errors and the Oath of 1272

By the 1260s conservative theologians adopted a new tactic: instead of banning entire works, they began to condemn particular ideas in Aristotle’s works that they regarded as dangerous and offensive. One of the leaders of the conservative faction was Bonaventure (John Fidanza, 1221-1274), a knowledgeable Aristotelian scholar who thought some of Aristotle’s ideas were too dangerous for the faith and should be rejected by all Christians. In 1270, he and his colleagues persuaded the bishop of Paris, Etienne Tempier, to condemn thirteen errors that were derived from the works of Aristotle and his Muslim commentator Averroës. Three errors were directly relevant to the relations between natural philosophy and theology. Two condemned, in different ways, the belief that the world is eternal, and a third condemned the idea that all phenomena below the moon depended on the celestial bodies, which was the basis for astrology, a widely used discipline opposed by the church.

As a further protection against the potential dangers of natural philosophy, a papal legate in 1272 convinced the professors of logic and natural philosophy in the faculty of arts at the University of Paris to swear an oath that “no master or bachelor of our faculty should presume to determine or even to dispute any purely theological question, as concerning the Trinity and incarnation and similar matters.” Because arts masters were not trained to consider theological questions, they now had to swear that they would not do so, a practice that remained until the end of the fifteenth century. If any arts master perhaps inadvertently confronted a question that touched both faith and philosophy, he had to resolve it in favor of the faith or be excommunicated. Only students or masters of theology were judged qualified to apply natural philosophy to theological problems. While arts masters were not to mix natural philosophy and theology, theologians could use as much natural philosophy as they wished to resolve or explain any theological question.

As a consequence of the oath of 1272, natural philosophy remained relatively free of religious considerations, focusing exclusively on natural causation. In stark contrast, theology, as we shall see, imported so much natural philosophy into routine theological questions that they transformed theology into an analytical discipline that had little religious content.

A genuine rivalry existed between the arts and theology faculties at the University of Paris in the thirteenth century. The arts faculty was not regarded as the equal of the theology faculty, because the guardians of revelation were valued more highly than those who relied on human reason. This relationship was but a reiteration of the old doctrine that secular learning is the handmaiden to theology. Moreover, professional theologians, whether or not they were members of a faculty of theology, were important and often powerful members of the church. In Paris, they would have had ready access to the bishop or papal officials. It is not surprising, therefore, that they could easily dominate the arts faculties, whose teachers might have had clerical status but were neither theologians nor members of the clergy.

The Condemnation of 1277

Despite the condemnation of thirteen errors in 1270 and the oath of 1272, conservative theologians in Paris were convinced that numerous ideas and arguments contrary to the faith were being discussed and defended orally, and even written and disseminated. News of the disagreements in Paris reached Pope John XXI, who instructed the bishop of Paris, still Etienne Tempier, to investigate. Within three weeks, Tempier, at the instigation of his advisers and without final approval by the pope, issued a massive condemnation of 219 propositions drawn from many sources, including the works of Thomas Aquinas. Many of them were relevant to science. Some twenty-seven proclaimed, in one form or another, the eternity of the world, which contradicted church teachings about creation.

The eternity of the world became the most important philosophical and theological issue of the late Middle Ages. It was as central to medieval thought as the Copernican heliocentric theory was for the sixteenth and seventeenth centuries and the Darwinian theory of evolution from the nineteenth century to the present. A number of medieval natural philosophers believed that, in terms of natural arguments, the world is uncreated, but they then yielded to the faith and conceded that God has super-naturally created the world. Although he firmly believed in the creation of the world, Thomas Aquinas argued that no conclusive argument could be presented in favor of either creation or eternity. But faith requires one to believe in the creation of the world.

The Condemnation of 1277 had a considerable impact on natural philosophy and the way it was done. To discuss one of Aristotle’s conclusions that was contrary to some article of faith, a natural philosopher would cast the argument into a hypothetical format, so that the authorities would not think the author accepted it as true. For example, in considering the eternity of the world, an author might declare that he was assuming, along with Aristotle, the eternity of the world, from which assumption he could show that no species of being could have been actualized from a previous state of potentiality. Thus every species of being in existence must have been in existence previously and therefore had no beginning, and would presumably have no end, clearly indicating the eternity of the world. To avoid charges of heresy, a natural philosopher would usually declare, as did Siger of Brabant in the thirteenth century, that “we say these things as the opinion of the Philosopher [that is, Aristotle], although not asserting them as true.”

It was common for natural philosophers to use the expression “speaking naturally” when they wished it understood that they were speaking solely in terms of natural philosophy without regard to any theological implications. However, all natural philosophers knew that where pronouncements of faith conflicted with Aristotle’s conclusions, the faith must prevail.

God’s Absolute Power

Various articles in the Condemnation of 1277 shaped a different type of hypothetical argument, which was directed against Aristotle’s natural philosophy and rested instead in God’s absolute power to do anything short of a logical contradiction. Thus various interpretations that Aristotle had regarded as impossible—that is, which he regarded as “natural impossibilities” within his world system—came to be treated as hypothetical possibilities, solely because God could create such conditions by supernatural means.

The Possibility of Other Worlds

Condemned article 34 declares that “the first cause [that is, God] could not make several worlds.” This proposition was condemned because it upheld Aristotle’s opinion (in On the Heavens) that “there is not now a plurality of worlds, nor has there been, nor could there be.” Only one world is possible. The implication of Aristotle’s position is that if a plurality of worlds is impossible, not even God could create another world. Anyone who agreed with article 34 would be excommunicated. Although all were expected to concede that God could create other worlds, no one was required to believe that He had actually done so.

Despite the common belief in the Middle Ages that God did not and would not create other worlds, natural philosophers and theologians found it challenging to assume hypothetically that God had indeed done so. They then sought to determine what such worlds would be like, and whether they could coexist with our world. It was not unusual for natural philosophers to imagine that God created other worlds in different arrangements. He might have created an infinite number of successive worlds and may continue to do so into an eternal future; or He may have chosen to create a multiplicity of simultaneously existing worlds. Nicole Oresme, one of the most famous theologians and natural philosophers of the late Middle Ages, imagined concentric worlds: a world within our earth and a world enclosing our world. He even suggested that a world might exist within the moon. Although the existence of such worlds is improbable, they are not impossible, Oresme insisted, because “the contrary cannot be proved by reason nor by evidence from experience.”

Medieval natural philosophers usually imagined that if God did create other worlds to coexist with ours, these worlds would be replicas of our world, although each would be self-contained and operate independently of all other worlds. Thus, contrary to Aristotle’s central argument that only one center and circumference could exist and therefore only one world, scholastics believed that it was at least possible many worlds could coexist simultaneously, and consequently so could many centers and circumferences.

God and Infinite Void Space

Aristotle had argued that nothing existed beyond our unique world—neither matter, nor vacuum, nor place, nor time. Medieval natural philosophers agreed with Aristotle that these entities did not exist beyond our real physical world. But in the hypothetical worlds that God might create, they imagined that matter could indeed exist beyond our world if God chose to create other worlds beyond ours. Moreover, they imagined that if God did create those other worlds, void spaces would exist between them, and hence contrary to Aristotle’s claim, the existence of void space was at least possible. In fact, despite Aristotle’s rejection of extracosmic void space, a number of medieval theologians assumed the actual—not hypothetical—existence of such a space. Theologians were concerned about God’s location in the world. They were convinced that God could not be confined to the finite world He had created. As an infinite being, it was only fitting that He be omnipresent in an infinite void space. Indeed, they identified the infinite void space with God’s infinite immensity.

Because God was regarded as an incorporeal being without dimensions, theologians insisted that the infinite void space, which was identified with God’s immensity, was itself dimensionless. As Thomas Bradwardine, an eminent fourteenth-century theologian and mathematician, expressed it: God “is infinitely extended without extension and dimension.” The belief that God is omnipresent in an infinite, extracosmic void space became commonplace in the early seventeenth century. It was accepted by the great English scientist Isaac Newton, who assumed the existence of an infinite void space in which God was substantively omnipresent and, as Newton explained, “suffers nothing from the motion of bodies” and where “bodies find no resistance from the omnipresence of God.” But Newton and others in the seventeenth century regarded void space as three-dimensional and therefore that God is a three-dimensional being, thus radically departing from their medieval predecessors.

Motion in Void Space

Medieval natural philosophers agreed with Aristotle that in our cosmos no vacuum could exist, or come to exist, by natural means, a belief that was summed up by a famous aphorism: “nature abhors a vacuum.” This dictum was accepted without dissent during the Middle Ages and remained unchallenged until the seventeenth century, when experiments finally led to its rejection. Despite their unanimous agreement with Aristotle that nature abhors a vacuum, medieval natural philosophers departed radically from Aristotle’s interpretations. Although they readily conceded that vacua could not exist by natural means, they assumed that God annihilated all the matter within the world, or part of the world. They also questioned Aristotle’s most important conclusions about motion in void space. Aristotle’s view was that such motion would be unintelligible and impossible, because in the absence of any material resistance, a body’s motion in void space would be instantaneous—that is, it would be moved with an infinite velocity.

In responding to Aristotle, scholastic authors devised a series of interesting counterarguments to show that if a vacuum did exist, motion in it would be finite and therefore like any ordinary terrestrial motion. They argued that bodies moving in a void space possessed their own internal motive force and internal resistance to that motive force. In this manner, they met Aristotle’s preconditions for finite motion in the real physical world, namely a motive force and a resistance to that motive force to prevent the body from moving instantaneously.

Another significant proposition condemned in 1277, article 49, asserted that “God could not move the heavens [or world] with a rectilinear motion; and the reason is that a vacuum would remain.” To deny that God could move the world with a rectilinear motion just because a vacuum would remain where once the world had rested was tantamount to restricting God’s absolute power and supporting Aristotle, who had rejected the existence of void space anywhere, and under any circumstances. Although they might have ignored this article, some theologians were moved to inquire what would happen if God did indeed move the world with a rectilinear motion. Nicole Oresme regarded such a motion as an absolute motion, since there would be no other motion to which it could be compared. Within Aristotle’s system of the world, such a rectilinear motion was inconceivable.

Natural Impossibilities

Medieval scholastic theologians departed from Aristotle’s physics and cosmology on many vital points. They did this by showing that phenomena Aristotle regarded as impossible were indeed possible by God’s supernatural power. Some of these phenomena were derived from articles condemned in 1277; others were extensions of God’s absolute power to situations not included in the articles. What emerged was a series of interesting speculations, or thought experiments, in which certain Aristotelian principles were challenged and even subverted. The invocation of God’s absolute power to annihilate all matter or move the world with a rectilinear motion despite leaving behind a void space proved to be powerful methodological tools. In the seventeenth century, they were adopted by natural philosophers such as Pierre Gassendi and Thomas Hobbes. Walter Charleton, an English follower of Gassendi, declared that the most laudable act of philosophers was to assume “natural impossibilities.”

Medieval appeals to God’s absolute power, however, had little, if any, religious motivation. Wherever we find it in medieval theological and scientific literature, it is almost never intended to make a religious point. Theologians had become addicted to an analytical approach to theology that used natural philosophy, logic, and even mathematics to explicate a great variety of questions that were only superficially theological. They were actually exercises in philosophical analysis. The most significant form of medieval scholastic literature in both natural philosophy and theology was in the form of questions, almost always beginning with the word “whether.” There were questions about other worlds, about God’s powers, about the infinite and infinity, and numerous questions on various aspects of motion, including the motion of angels. Theologians often asked whether God could make other worlds; whether God could make a better world than this world; whether God knew that He would create a world from eternity; whether God could make a creature exist for only an instant; whether God could make some actual infinite with respect to dimension or multitude; whether an angel could be moved from place to place successively in some time; whether an angel could be moved from place to place in an instant. The replies to these questions were usually couched in the analytic language of logic and natural philosophy.

The criterion for determining whether God could or could not do any particular act was the principle of noncontradiction, which asserts that a statement and its negation cannot both be true at the same time. If the action involved God in a contradiction, it followed that God could not perform the act in question; if no contradiction was involved, it was assumed that God could perform the action. For example, some theologians and natural philosophers denied that God could make an actually infinite thing or dimension, because if God did create an actual infinite, He could not create anything greater than that infinite, because it is absurd to suppose that there is anything greater than an infinite. Although this was equivalent to setting limits on God’s absolute power, it was an essential move, because it is a contradiction to suppose the possible existence of anything greater than an actual infinite.

Some theologians conceived of yet other paradoxical ways by which God’s power might be thwarted by imaginary theological dilemmas using logical and mathematical arguments. In the fourteenth century, English theologian Robert Holkot applied the medieval doctrine of first and last instants to the following imaginary situation: A man is alternately meritorious and sinful in the last hour of his life. He is meritorious during the first proportional part of his last hour and sinful in the second proportional part; he is again meritorious in the third proportional part, and again sinful in the fourth proportional part, and so on through the infinite series of decreasing proportional parts up to the instant when death occurs. Because the instant of death is not part of the infinite series of decreasing proportional parts of the man’s last hour, it follows that there is no last instant of his life and, therefore, no last instant in which he could be either meritorious or sinful. Therefore God cannot judge him. In this rather strange, even bizarre, manner, Holkot devised a logical argument in which God is stymied and unable to render a judgment on someone just deceased. Holkot, however, was simply applying the medieval concept of first and last instants to the infinite divisibility of a continuum. Many theologians engaged in similar tactics, since virtually all of them were familiar with such logico-mathematical techniques that were frequently used to resolve paradoxical situations.

Theologian Natural Philosophers

The emergence of the theologian natural philosophers in the late Middle Ages was a monumental occurrence and was instrumental in shaping the history of science in Western Europe. All theologians who wrote more than cursorily on natural philosophy, whether in straightforward treatises on natural philosophy or by importing natural philosophy into their theological commentaries, may be appropriately characterized as theologian natural philosophers. Earlier in the history of Western Christianity, Greek natural philosophy and science were to be used only as “handmaidens to theology,” not studied for their own sakes. Relatively little natural philosophy posed a direct challenge to the church until Greco-Arabic science and natural philosophy, especially Aristotle’s natural philosophy, became available in the twelfth and thirteenth centuries. Its eager acceptance by both arts masters and most theologians worried more conservative theologians, who used their influence to ban or expurgate the works of Aristotle. There is no doubt that the reaction to the Condemnation of 1277 played a significant role in reshaping medieval Aristotelian natural philosophy. Appeals to God’s absolute power to do anything short of a logical contradiction produced a series of bold, hypothetical questions about the physical world and beyond that world. Such stimulating, imaginary questions—most of them about “natural impossibilities” in Aristotle’s physical world—emerged in both natural philosophy and theology.

By the end of the thirteenth century, the old “handmaiden to theology” role was occasionally paid lip service but was largely ignored. The explanation is simple: theologians were as enthusiastic about Aristotle’s logic and natural philosophy as were the arts masters in the faculties of arts. Theologians studied these disciplines as much for their own sakes as for their utility in explaining scripture and the articles of faith. Even conservative theologians, such as Bonaventure, recognized the great utility of Aristotle’s natural philosophy, not just for explaining matters of faith, but also for understanding the operations of the physical world. Indeed, if theologians had decided to oppose Aristotelian learning as dangerous to the faith, Aristotle’s works could not have become the focus of studies at the universities. But they had no good reason to oppose it, since Western Christianity had a long tradition of using pagan thought for its own benefit. Difficulties arose as they adjusted to Aristotle’s thought, but in time—by the end of the thirteenth century—that adjustment had been made and many came to study Aristotle because of their genuine interest in natural philosophy for its own sake.

It should be emphasized that no effort was ever made in the West to Christianize Aristotle and secular learning. Natural philosophy was viewed as an essential discipline for understanding a world that God had created but left to operate rationally, according to natural laws He had devised. Natural laws were not to be explained by appeals to holy scriptures or miracles. It was the business of natural philosophy, not theology and religion, to explain the natural workings of the world. Ironically, it was theologians, thoroughly trained in natural philosophy when they were students in the arts faculties before matriculating in the higher faculty of theology, who were the most innovative and imaginative interpreters of Aristotle’s natural philosophy. Because of this dual capacity, it is appropriate to regard them as a class of theologian natural philosophers.

To understand why theologian natural philosophers were more important for the development of natural philosophy than the arts masters who taught natural philosophy and logic, one need only understand that arts masters were not trained in theology and were either forbidden to introduce theological issues into their natural philosophy, as at the University of Paris, or were reluctant to do so, because they knew theologians would be weighing their every word and would denounce them if they were viewed as jeopardizing the faith in any manner. By contrast, the theologians, who were trained in both theology and natural philosophy, could readily apply science or natural philosophy to theology and, conversely, theology to science and natural philosophy. But while they frequently applied natural philosophy to theology, they rarely ever applied theology to natural philosophy, because, like their colleagues in the arts faculties, theologians used natural philosophy to provide natural—not super-natural—explanations for the physical phenomena of the world.

Reason and the Medieval University

The natural philosophy that was developed in the medieval universities in both the arts and theology faculties was firmly based on the use of reason. For virtually all questions considered, the authors presented affirmative and negative arguments and then defended the position they deemed correct. All scholastic natural philosophers were trained to argue in rational, analytic terms, and medieval natural philosophy is a model of reasoned argumentation. Theologians were not only the most imaginative contributors to natural philosophy, but some also made significant contributions to science and mathematics, as the names of Albertus Magnus, John Pecham, Theodoric of Freiberg, Thomas Bradwardine, and Nicole Oresme bear witness. Theologians had a remarkable degree of intellectual freedom and were careful not to allow their theology to hinder inquiry into the structure and operation of the physical world. Biblical texts were not used to “demonstrate” scientific truths by blind appeal to divine authority. That would have been regarded as futile and unproductive.

Christianity benefited from the fact that it developed within the Roman Empire and thereby had an opportunity to adjust to secular, pagan learning, which it used to help explain the faith. For the long term, it was also important that Western Christianity, unlike the Byzantine Orthodox Church or Islam, accepted a separation between church and state, and analogously kept natural philosophy and theology as distinct disciplines. The emergence of early modern science was greatly facilitated by the fact that medieval theologians did not inject the supernatural into natural philosophy. They were interested in resolving virtually all questions by means of logic and reason. Indeed, both natural philosophy and theology became analytic disciplines. It was because of this great emphasis on reason, that medieval scholars prepared the way for the emergence of early modern science in the sixteenth and seventeenth centuries.

But the emphasis on reason alone would not have been sufficient. The techniques of analysis and argument that were developed at the medieval universities had to become widely disseminated and deeply rooted. Natural philosophy was an old discipline, but never in any society had it been extensively practiced and widely disseminated. It was always the study of a few individuals located here and there. But the medieval university changed all that. Universities were located all over Europe; by 1500 there were approximately seventy-five, each teaching logic and natural philosophy as a basic curriculum. Since all the sciences that emerged as independent subjects centuries later were fragmentarily embedded in medieval natural philosophy that was taught at the universities, one can legitimately claim that science and scientific modes of thought were already deeply embedded in medieval society.

Important features of science—such as experiment, careful observation, and the consistent application of mathematics to real physical problems—were not part of the approach to medieval science. Natural philosophers and scientists would add them in the seventeenth century. But the indispensable use of reason and analysis were made routine during the Middle Ages, without which modern science could not have come into being. The emergence of the universities and the class of theologian natural philosophers made it possible for natural philosophy to develop and flourish in ways that had never before been feasible. This background to early modern science explains why, after the thirteenth century, there was a general absence of a science-theology controversy in Western Europe until the condemnation of Galileo in 1633.