Major points of conflict existed between Church doctrine and ideas espoused in the natural books of Aristotle. The introduction of Aristotle's works into Latin Christendom in the thirteenth century was potentially problematic for the Church and its theologians. Although a clash was hardly inevitable, it was not long in coming. It seems to have hit hardest at the University of Paris, which not only had the greatest theological school of the Latin Middle Ages but also had one of the best and largest arts faculties. And yet, the conflict that developed must never be allowed to obscure the most important fact: that the translated works of Aristotle were enthusiastically welcomed and highly regarded by both arts masters and theologians. Indeed, Aristotle's philosophy was so warmly received that try as they might, the forces arrayed against it could not prevail.

THE CONDEMNATION OF 1277

The struggle against Aristotle was concentrated in the University of Paris and its environs. In 1210, soon after Aristotle's works in natural philosophy had become available in Latin, the provincial synod of Sens decreed that the books of Aristotle on natural philosophy and all commentaries thereon were not to be read at Paris in public or secret, under penalty of excommunication. Confined to the locale of Paris, this ban was repeated in 1215, specifically for the University of Paris.

The division of the Roman Empire from the late third century onward into an essentially Greek-speaking eastern part and a Latin-speaking western part had a momentous consequence for intellectual life and therefore for the history of science and natural philosophy. With the passage of time, knowledge of the Greek language in the Western empire became relatively rare. Because Greek had been the language of science, this meant that Greek science was essentially unavailable to those whose sole language was Latin. To become accessible to the Latin-speaking West, a Greek scientific treatise had to be translated into Latin. Few treatises were. Apart from a small number of Hippocratic medical treatises and the few translations made by the likes of Chalcidius and Boethius, almost no significant works of Greek science were translated into Latin. During the ninth and tenth centuries, when the Arabs were translating a large portion of Greek science into Arabic and also adding to this legacy, and during the period when Greek science continued to be read and studied in the Greek-speaking Byzantine Empire, the West had before it only the rudimentary science of the Latin encyclopedists already described in chapter 1. By a.d. 500, knowledge of Greek had become rare and knowledge of the exact sciences even rarer. Except for occasional translations, which sometimes failed to circulate or perished completely, little was added to the now dominant encyclopedic tradition.

Many of the Aristotelian principles and concepts described in chapter 4 were retained in the Middle Ages. These concepts – element, compound, matter, form, the doctrine of contraries, the four types of change, celestial incorruptibility, and others – were too fundamental to be abandoned or even altered significantly. Numerous other of Aristotle's arguments and ideas, however, were changed considerably and sometimes wholly replaced. The most significant transformations in Aristotle's natural philosophy during the late Middle Ages, from the standpoint of the history of science, occurred in his treatment of motion. Here the departures were truly dramatic. Aristotle's explanations of natural and violent motion were largely abandoned, especially those on violent motion.

One striking departure occurred in Aristotle's basic formulation as described in chapter 4. There we saw that for Aristotle V∝ F/R, where V is velocity, F is motive force, and R is the total resistance offered to the applied force, a quantity that, presumably, includes the resisting object or body plus the resistance of the external medium in which the motion occurs. To double V, R could be halved and F held constant; or, F doubled and R held constant. To halve V, F could be halved and R held constant; or R doubled and F held constant. Aristotle realized that in halving a velocity F might be reduced to the point where it was smaller than R and therefore unable to move it.

A description of the structure and operation of the medieval universities is essential because of the importance of these institutions for the development of Western science. The universities had emerged as a result of the transformation of society and intellectual life that had occurred in Western Europe by the twelfth century.

The highly feudalized Europe of the seventh and eighth centuries was drastically altered by the eleventh century. During the late eleventh and twelfth centuries, political conditions improved dramatically, due in no small measure to French-speaking feudal lords who brought reasonably stable governments to Normandy, England, Italy, Sicily, Spain, and Portugal. The vigor of a revitalized Europe is also evidenced by the reconquest of Spain, which was well underway by the end of the eleventh century.

With the establishment of greater security, Europe's economy revived, and the standard of living rose for all segments of society. This was occasioned by significant agricultural improvements, most notably the advent of the heavy plough, to which the horse was now harnessed instead of the ox. This substitution was made possible by the introduction of the nailed horseshoe and the collar harness, which together made horses far more effective agricultural engines than oxen. No less significant was the replacement of the two-field system of crop rotation with the three-field system, which also allowed for a major increase in food production.

Aristotle's natural books formed the basis of natural philosophy in the universities, and the way in which medieval scholars understood the structure and operation of the cosmos must be sought in those books. By his use of assumptions, demonstrated principles, and seemingly self-evident principles, Aristotle imposed a strong sense of order and coherence on an otherwise bewildering world. Aristotle's medieval disciples, who formed the class of natural philosophers during the late Middle Ages, would eventually extend Aristotle's principles to activities and problems beyond anything that the philosopher himself had considered.

Aristotle was convinced that the world he sought to understand was eternal, without beginning or end. He regarded the eternity of the world as far less problematic than any assumption of a cosmic beginning that also implied a future end to the world. It was better to postulate eternity than be forced into an explanation that required an infinite regress of causal beginnings. The idea that matter could have a beginning seemed impossible to the ancient Greeks, for if one were to arrive at some alleged pristine matter, it would inevitably lead to the question of what caused it, and so on. Without a beginning, however, the world could not have been created, and thus Aristotle's ideas about the eternity of the world set him in opposition to the theologians of the great monotheistic religions of Judaism, Christianity, and Islam.

During the first four centuries of Christianity, the Roman Empire was a geographical colossus, extending from the Atlantic Ocean in the west to Persia in the east, and from Britain in the north to regions south of the Mediterranean Sea. Within this Greco-Roman world, Christianity was born and disseminated. Its birth and early development occurred in a period of vast religious change and economic upheaval. For the first two hundred years of its existence, Christianity was no more visible and noticeable than many other of the numerous mystery religions and cults that had proven attractive to people at all levels of society. The sense of comfort that pagans derived from their belief in the traditional Homeric and Roman gods of the state religions was disappearing. The new cults – for example, Isis, Mithras, Cybele, and Sol Invictus (Unconquered Sun), as well as Gnosticism and Christianity – that were replacing the traditional deities not only borrowed ideas and rituals from one another but also came to share a few basic beliefs. The world was evil and would eventually pass away. Humans, sinful by nature, could achieve never-ending bliss only if they turned away from the things of this world and cultivated those of the eternal spiritual realm. Along with practicing varying degrees of asceticism, many of the cults believed in a redeemer god who would die in order to bring eternal life after death to his faithful followers.

Because Aristotelian natural philosophy is the major emphasis in this volume, our discussion of it must necessarily encompass Aristotle's natural books (libri naturales), as described in chapter 3, and the medieval commentaries and questions on those works. The natural books of Aristotle were far from a thorough, well-rounded, coherent, and systematic description and analysis of the physical world. But in those treatises, a wealth of topics and ideas were included, and a remarkable breadth of coverage. The natural books were the best available guides for the study of the universe, which is why they served as the fundamental texts for natural philosophy in the universities of the Middle Ages. It was that natural philosophy that functioned as the world view of the Middle Ages, a world view that was embodied in a special kind of literature – the questions literature – that was peculiar to the Latin Middle Ages and to the medieval university.

THE QUESTIONS LITERATURE OF THE LATE MIDDLE AGES

The questio, or question, was the most widely and regularly used format for natural philosophy. As we saw in chapter 3, it grew out of the commentary, but it was structurally akin to the oral disputation that was such a prominent feature of medieval university education. It was actually a teaching master's written version of the questions that he presented orally in his classroom lectures.

It is fun to think for oneself about grand intellectual issues. This book focuses upon some of the big questions about science. Little attention is paid to the personalities or politics of the science studies area on which it builds. It stands back from the literature of its field, avoiding reliance on arguments from disciplinary authority and ignoring the shorter swings of disciplinary fashion.

The big questions about science are those which try to assess what science has accomplished and what it might yet achieve. The traditional image of science as progressively building reliable knowledge of external reality on a foundation of secure fact, has had its underlying assumptions effectively criticised, especially by the present generation. There is a new image available. Science is merely a prominent form of socially legitimated belief in modern society. As society moves from depending on an aristocracy of learning to a free market in ideas, science moves from the consensual pronouncements of an institutionalised international orthodoxy to multi-faceted linguistic codifications of the culture of competing local forms of life.

The new image is not entirely persuasive. The practical ways in which science affects our everyday lives seems to require that science contains at least approximate truth about reality. In science studies, debates occur between the older philosophically oriented view and the newer view of science as a social construction (e.g. Kitcher, 1993, which follows a similar strategy to the present book). The older view asked the big questions but answered them unsatisfactorily, while the newer view has put much more limited questions in their place.

Introduction

This book has extended a fallibilist realist conception of science in terms of the view that we change our immediate reality in terms of our ideas while simultaneously changing our ideas to match reality. It has conceded to scepticism that we do not reach certainty in scientific conclusions; the fragments of fully explicit scientific reasoning are set within frames of optimising judgements about wider considerations. The rigorous science that we explicitly consider depends on contextual assumptions which are subject to change. At least some values are present even in our most nearly objective conclusions. Inevitably, then, the way we evaluate science is affected by local and short term factors. I have argued that there are many cognitive frameworks in an open society and that we produce science by trying to reconcile them at several levels of cognitive activity. In this way we hope to minimise the dependence of science on very localised contexts. So far I have offered techniques for optimising scientific judgements in the present. Must we lose touch with the science of the remoter past? Must future science be unclear to us? Are we locked into our own historical period? It would be unfortunate if we were. Relativism across time is as problematic a philosophy as relativism across the spatially dispersed cultures of the present. On such a view, we could not hope to understand the past and we could not hope to anticipate the future.

Rationality

One of the intellectual skills we have inherited from the ancient Greeks is a way of formalising arguments by laying down explicit rules which ensure that a conclusion reached from true premises is also true. These rules of valid reasoning were elaborated by the ancient Greeks into deductive systems such as Aristotelian syllogistic logic and Euclidean geometry.

The success of this tradition made explicit formalised deductive reasoning into a model for all reasoning. It made argument the primary form of rationality and explicit argument according to universally agreed rules became a skill inculcated by education and applied widely in systematised learning. Our ideals of knowledge came to be shaped around this model of rationality. We should strive to formulate our ideas in statements, beginning with assertions about which there is minimal room for doubt, building on this firm foundation with valid reasoning that preserves truth at every step. Because such reasoning is explicit, it can be publicly scrutinised. Because it is valid, it does not depend on who produced it or where it is produced, but holds for anyone who is prepared to accept the premises.

Aristotelian syllogistic logic (which renders reasoning as triads of statements, in which the conclusion follows from two premises, according to a limited set of rules, e.g. ‘All men are mortal’ / ‘Socrates is a man’ / Therefore ‘Socrates is mortal’) was the main model of deductive reasoning for more than two millennia. However, it was increasingly clear that it was too limited for the grand aims described.