By the beginning of the thirteenth century, the major treatises of Greek and Arabic origin in science and natural philosophy were available in Latin translation. It is almost certain that lectures were being given on at least some of Aristotle's books on natural philosophy at the new universities of Oxford and Paris in the first decade of the thirteenth century. This is evident from the fact that in 1210, the Parisian Synod decreed, among other things, that “no lectures are to be held in Paris either publicly or privately using Aristotle's books on natural philosophy or the commentaries, and we forbid all this under pain of excommunication.” The prohibition of 1210 is a good indication that Aristotle's works on natural philosophy were readily available, for otherwise there would have been no need to ban public and private lectures on them. Although the University of Paris is not specifically mentioned in the decree, it is virtually certain that mention of public lectures is a reference to lectures at the university. To place medieval natural philosophy in its proper context, it is essential to describe the structure and character of the universities, which were indeed the “proper context” for Aristotle's natural philosophy and the commentaries on, and elaborations of, it. Indeed, it is almost as if the universities of Oxford and Paris, and their numerous successors, came into being to serve this function.

THE MEDIEVAL UNIVERSITY

In the course of the eleventh and twelfth centuries, Europe had rapidly become urbanized.

Aristotle's natural philosophy and Greek science generally did not begin to enter Western Europe until the middle of the twelfth century. Before that time, only a minuscule part of Greek science and natural philosophy was available in the West. The Romans had not been sufficiently interested in such subjects to translate relevant Greek texts into Latin. But some Roman authors wrote treatises that modern scholars would regard as primarily concerned with natural philosophy. Among those in this group who have left extant treatises, the most famous are Lucretius (ca. 95–ca. 55 bc), Seneca (ca. 4 bc–ad 65), and Pliny the Elder (ca. ad 23–79).

ROMAN AUTHORS

The fame of Lucretius derives from his great poem, On the Nature of Things, which presents a picture of nature based on the atomic theory of Epicurus (341–270 bc), a Greek philosopher. Lucretius dealt with many topics, but the most important was his cosmic vision based on an assumption of an infinity of worlds, each composed of atoms moving in an infinite void space. He assumed that each world comes into being by a chance coming-together of atoms in the void; eventually each world passes away when its atoms dissociate and move into the void to form parts of other worlds. Lucretius was largely ignored by medieval Christianity, because of his attacks on religion and his denial of a created world, as we see in his statement that “our starting-point will be this principle: Nothing can ever be created by divine power out of nothing.”

THE PRELITERATE BEGINNINGS

Natural philosophy began with no name to designate it, and in its embryonic phase it included just about anything relevant to nature. Until the time of Aristotle, who shaped the discipline of natural philosophy for the following two thousand years, the study of nature may be said to have embraced all inquiries and questions about the physical world. On what is such a claim based? Surely it is not based on anything said or recorded. But we may reasonably interpret the earliest form of natural philosophy as embracing “all inquiries about the physical world” because we have no reason not to do so. Natural philosophy may be said to have begun with the first efforts to understand the world by the earliest human beings in their fight for survival. Thus, it extends to preliterate societies, which, for thousands of years, amassed knowledge about the world, which they passed on to subsequent generations.

Members of preliterate societies learned by empirical methods about the habits of this or that animal, or this or that plant, or devised explanations, either magical or natural, about this or that individual natural phenomenon. They must have gleaned knowledge about nature from hunting and from the earliest kinds of agriculture in which they engaged. “But to have the idea of the nature of some particular object is not to have the general conception of a domain of nature encompassing all natural phenomena.”

From its high point in the in the fourteenth century, medieval natural philosophy underwent significant changes in the course of the sixteenth and seventeenth centuries. But just as important as the changes that occurred directly to medieval natural philosophy are the changes that significantly altered almost everything around it. By the seventeenth century, Western Europe had undergone a great transformation from what it had been like in the fourteenth century. Beginning with Gutenberg's invention of the printing press around 1450, followed by Columbus's voyage to America in 1492, and, in the seventeenth century, the inventions of the microscope and telescope, the world in which Aristotle's natural philosophy was developed and nurtured had largely vanished. No doubt other factors of change might be cited, but one that also must be mentioned is the Protestant Reformation, which directly challenged the Catholic Church and therefore the culture within which Aristotle's natural philosophy had flourished. Aristotle's dominance in natural philosophy during the late Middle Ages is partially, if not largely, explicable by the fact that until the first half of the fifteenth century, Aristotelian natural philosophy had no rivals. From the mid-fifteenth century on, this began to change dramatically, as Greek works previously ignored or unknown were translated into Latin and vernacular languages and began to have an impact. Soon rival philosophies emerged among which were Platonism, Atomism, Stoicism, Neoplatonism, Hermeticism, and Copernicanism.

The critical spirit of inquiry that developed and even flourished in Western Europe during the twelfth century was, as we saw, confined to interpreting and elaborating a by-then traditional body of Latin learning that was largely Platonic and Neoplatonic. But even as they exercised their intellects on the old learning, they had become aware that there was a body of learning of which they were ignorant. As Christians slowly wrested control of much of Spain and Sicily from Islamic rule, they came into contact with Islamic culture and the Arabic language. They not only learned of a large body of learning in the Arabic language but also that there were treatises in Greek. We may assume that the literature in the Greek and Arabic languages ranged over the whole spectrum of learning, extending from the humanities and literature to science and natural philosophy. Western interest in this body of literature focused almost exclusively on logic, science, and natural philosophy, largely ignoring the rest of it. The translations from Arabic and Greek to Latin occurred during the twelfth and thirteenth centuries. The lengthy process represents what is probably the greatest intellectual expropriation of knowledge by one culture and civilization from other cultures and civilizations.

THE WORLD OF THE TRANSLATORS

The translators came from all parts of Europe and worked alone or collaboratively.

Most of my publications over many years have in one way or another been about, or concerned with, natural philosophy. In all those years, however, neither I nor anyone else has seen fit to write a history of that discipline. Although numerous histories of science have been published, and will undoubtedly continue to appear, I am unaware of any history of natural philosophy. It occurred to me that an account of the historical evolution of natural philosophy should prove helpful to a better understanding of the development of the history of science itself. Indeed, as readers will discover, the historical relationship between natural philosophy and science is by no means straightforward. Opinions about their association and interconnections have often been controversial and sometimes quite elusive.

Once I determined to write a history of natural philosophy, I had to decide whether that history should be all encompassing – from its origins to its general replacement by modern science – or whether it should be confined to one or two historical periods. Because my area of specialization has been the late Middle Ages, it seemed plausible to begin with the origins of natural philosophy in the ancient world and conclude at about 1500, when medieval natural philosophy reached the height of its development. Around 1998 I became aware of an opinion that claimed that natural philosophy was always about God, even when God is not discussed or mentioned; and, consequently, that natural philosophy could not be science, because the latter was never about God.

To understand the substantive character of natural philosophy, it is essential to describe the kinds of literature in which medieval natural philosophers expressed their thoughts. In Chapter 7, I mentioned the two most basic forms of scholastic literature: (1) the commentary on a text and (2) the questions format in which the author, or commentator, formulates a series of questions on Aristotle's text, posing the questions sequentially in the order of the text. Examples from both of these types will illustrate the most fundamental methods of conveying natural philosophy to a broad audience.

Textual Commentaries on the Works of Aristotle

In the preceding chapter, I distinguished four varieties of textual commentaries. Because the first two methods were used primarily for teaching and conveyed little of the commentator's opinions, I shall illustrate only the third and fourth types. The third type was that in which the commentator separated his commentary from the text on which he was commenting. This could take two forms, the first of which involved a section-by-section sequential commentary on the text, while the second was a paraphrase of Aristotle's text.

The section-by-section sequential commentary was probably the most popular and probably the easiest to follow. In this method, the commentator cited a section of Aristotle's text followed by his commentary on that passage, a technique that derived from Averroes, the great twelfth-century Islamic commentator, who quoted a section of Aristotle's text followed by comments, in which he explained Aristotle's meaning and intent.

Although the early centuries of Christianity played a significant role in shaping the relations between natural philosophy and theology in the Middle Ages, developments in the twelfth and thirteenth centuries were more directly relevant in establishing the interplay between these two enormously important disciplines, an interplay that may appropriately be interpreted as surrogate for the relationship between science and religion. Nevertheless, to better appreciate and understand the long-term connections and antipathies between these two disciplines, it is desirable to describe briefly the manner in which they began their relations in the early centuries of the rise and development of Christianity.

When Christianity first emerged within the Roman Empire, pagan culture and literature were already centuries old. The fact that Christianity, in contrast to Islam some centuries later, was disseminated rather slowly – it was not until 392 ad that Christianity became the state religion, almost four centuries after it first emerged – enabled Christians to adjust to pagan philosophy and literature and to contemplate what role, if any, it might play in their religion. Those who were instrumental in shaping the attitudes of the early Church toward pagan philosophy, and especially natural philosophy are known collectively as the Church Fathers. They came to represent two major approaches toward pagan natural philosophy. The first approach was quite hostile, regarding pagan science and philosophy as of little use to Christianity and even potentially harmful.

Although Neoplatonism and Neoplatonic interpretations of Aristotle's works shaped the understanding of Aristotle's ideas in late antiquity in the Greek world of the Byzantine Empire, Greek science, medicine, and natural philosophy, especially Aristotle's natural philosophy, were disseminated eastward into Syria and Persia, largely by way of translations, first from Greek into the Syriac language, and then Syriac and Greek into Arabic. Religious tensions and animosities were the major catalyst for this eastward thrust of Greek science and natural philosophy. To strike a blow against paganism, the Roman Emperor Justinian closed the Neoplatonic philosophical school in Athens in 529 ad. A number of the philosophers at the school, including Simplicius, opted to move to Persia and continue their philosophizing under the aegis of the Persian king, Chosroes. In time, however, all of these philosophers chose to return to the Byzantine Empire. King Chosroes made an arrangement with Emperor Justinian to allow their return on condition that Justinian would not coerce them into embracing the Christian faith. Justinian honored his commitment and the returning philosophers lived in peace.

THE TRANSLATIONS

But the major problem for the Byzantine Empire derived from two schismatic sects, the Nestorians and Monophysites. The Nestorians took their name from Nestorius, who had been a monk in Antioch but was made Patriarch of Constantinople in 428. Anastasius, who also had been a monk in Antioch, insisted that the Blessed Virgin Mary was the mother only of the human body of Christ, and not of Christ's divinity.

LIFE

Aristotle was born in 384 bc, in the town of Stagira, which lay in Macedonia in northern Greece. His father was Nicomachus, a physician, in the service of King Amyntas of Macedon; his mother was Phaestis, a woman of independent wealth. In 367, as a lad of seventeen, Aristotle moved to Athens to study with Plato in the Academy, where he remained for twenty years, until the death of Plato in 347. It is plausible to assume that during those twenty years, Aristotle heard, and participated in, important philosophical discussions involving some of the greatest minds of the time. The themes that were debated must surely have ranged across issues that were dear to Plato, such as metaphysics, ethics, logic, politics, and epistemology. And although physics and cosmology were not themes to which Plato devoted much time and effort, Aristotle must surely have had occasion to engage in discussions about those subjects.

With the death of Plato in 347 and the emergence in Athens of anti-Macedonian sentiment, Aristotle, who never became an Athenian citizen, departed Athens and traveled to the coast of Asia Minor. There, he lived first in Assos, where he married Pythias, the niece of Hermias, the tyrant of Assos. He moved next to Mytilene, on the island of Lesbos, where he met Theophrastus, who became an important friend and future colleague. It is likely that during his approximately four years in this region, Aristotle studied marine biology and used what he learned in his biological treatises.

Aristotle, as we saw, restricted the scope of natural philosophy by defining it as a branch of theoretical knowledge just below metaphysics and mathematics. It was the discipline that studied bodies undergoing change and motion, which included virtually every physical body in the universe and thus seemingly embraced medicine and alchemy within the domain of natural philosophy. But that did not occur, largely, I suspect, because the extant works that came to be identified with the name of Aristotle did not include works on medicine and alchemy and these disciplines were, therefore, not regarded as belonging to natural philosophy.

NEOPLATONISM AND ITS APPROACH TO ARISTOTLE

Aristotle was obviously not the only one who wrote on subjects regarded as part of natural philosophy. But so overwhelming was his influence, and so numerous his works, that Aristotle's works on natural philosophy, or physics, came to be regarded as synonymous with that discipline. To express one's opinions and judgments on natural philosophy as understood by Aristotle, it became customary in antiquity to comment on Aristotle's works. The name of the first commentator, or commentators, is unknown. Indeed, how Aristotle's works fared during the first few centuries after his death is a mystery. But in the second half of the first century bc, Aristotle's fortunes changed dramatically as a result of the efforts of Andronicus of Rhodes, who produced an edition of the works of Aristotle that forms the basis on which subsequent texts were based.

As we look back on the history of science, it seems that a strong case can be made for the assumption that the emergence of modern science was in some significant and meaningful sense dependent on the existence of a well-developed natural philosophy. To establish this thesis, we must first go back to the late Middle Ages, when natural philosophy reached its mature development after it became a required subject in the medieval universities. Did this mature and institutionalized natural philosophy possess the requisite characteristics that would enable science in general, and the particular sciences that comprise it, to emerge in the centuries to follow?

Is this perhaps a pseudo-issue? Was it not true that during the late Middle Ages exact, or “middle,” sciences, such as astronomy, optics, and mechanics, already existed independently of, but concurrently with, natural philosophy? In truth, these exact sciences had themselves once been a part of natural philosophy as far back as the period just before Aristotle. In his classification of theoretical knowledge, Aristotle classified the exact sciences as independent of natural philosophy, because they were seemingly as much mathematical as they were natural philosophy; but they were neither mathematics nor natural philosophy. Nor were they sciences in the later modern sense. Why is this so? Precisely because they were mathematical disciplines that were only supposed to focus on limited problems that could be resolved only by mathematics but were not to be resolved by natural philosophy.