Realism and nominalism were the two major theoretical alternatives in the later Middle Ages concerning the reality of general objects: realists believed in the extramental existence of common natures or essences; nominalists did not. This so-called “problem of universals” was only one of the main questions at issue between realists and nominalists, however, whose disputes ranged widely over the status and mutual relationships of the basic items of the world (individual and universal substances, individual and universal accidents) as well as their connection to language. For scholastic authors, these questions arose first and foremost in the context of Aristotle’s Categories. As a consequence, the medieval realist–nominalist dispute included also the problem of the status and number of real categories. Realists held that the division into categories is first of all a partition of things made on the basis of ontological criteria and only secondarily a classification of terms (which could be mental, written, or spoken), and therefore that the world is divided into ten fundamental kinds of things (in a broad sense of ‘thing’), no one of which can be reduced to any other. In contrast, nominalists maintained that Aristotle’s division into ten categories is a partition of terms on the basis of semantic criteria, and that there are only two or three real categories (Substance and Quality, and perhaps Quantity too). Even though from a purely logical point of view these opinions on categories and universals are independent of each other, historically, in the later Middle Ages, realism concerning categories was always matched by a realistic conception of universals, whereas nominalism on the question of categories was always paralleled by a nominalistic position on universals.

There is very little content to the concept of modernity except as a term of contrast with antiquity and the Middle Ages, and what is signified as “modern” changes, depending upon the specific contrast one wishes to make. Historians often use the term to designate nineteenth-century phenomena such as the industrial revolution, the rise of capitalism, the institution of representative democracy, and urbanization. In philosophy, “modernity” is usually taken to refer to the period that discarded medieval or scholastic philosophy, beginning roughly in the sixteenth century and encompassing such intellectual movements as the Renaissance, the Reformation, and the Counter-Reformation, continuing in the seventeenth with what is called the Age of Reason (early modern philosophy), and culminating in the eighteenth with the Enlightenment.

THE COGITO AND MODERNITY

Of course, all of the terms above are imprecise and disputed, but few will disagree that the work of René Descartes typifies early modern philosophy and sets the agenda for the philosophers who came after him. So the question of philosophical modernity – namely, how best to describe the reasons for the rise of modern philosophy and the waning of scholasticism – may be resolved by determining the break one wishes to depict between the work of Descartes and that of the scholastics.

Numerous elements in Descartes’s Meditations have been considered modern and contrasted with scholastic philosophy; these have included his use of radical skepticism and his appeal to the first-person perspective – that is, the cogito – as the first principle of knowledge. These modern elements are sometimes contrasted with what is thought to be a residual scholastic element in Descartes’s thought, namely his use of a causal principle to prove the existence of God.

Most popular accounts of the introduction of Aristotle’s natural philosophy credit Arabic civilization with transmitting classical Greek works to the Latin West. By contrast, a few contemporary authors, hostile to Islam, deny any contribution of the Islamic world to scholasticism. Neither claim is credible. As we shall see, although Arabic Aristotelianism did not provide the primary access to Aristotle’s texts themselves, it did make a profound contribution to scholastic natural philosophy.

Confounding this dispute is a misunderstanding of the significance of Arabic-based Aristotle translations. Scholastic authors seldom commented on translations based on the Arabic Aristotle. Almost every major scholastic commentary on Greek philosophical works is based on a direct translation from Greek into Latin, with a few early exceptions. Scholastics evidently recognized that though they were often harder to follow and more obscure than translations from the Arabic Aristotle, Greek-based translations were closer to the original.

So let us look chiefly at the influence of the interpretative tradition of Arabic Aristotelianism on the Latin West, after saying a few words on translations of Arabic texts. We will suggest that though scholastics did not comment on Arabic-based translations of Aristotle, without these translations and more importantly without the interpretative tradition that accompanied them, the scholastic tradition would have been much poorer; indeed, it might never have arisen. After all, James of Venice’s translations had been available since about 1150, but Aristotelian analytics, metaphysics, and natural philosophy began to influence major scholastic authors only when the Michael Scot translations became available around 1225.

Many scholars are tempted to speak not of an emergence, but a rebirth or reawakening of thought in the Middle Ages, as if the ideas of antiquity had simply been put on hold for a while and then resumed. The image is, however, not just clichéd, but also misleading. We awake refreshed, perhaps, but not fundamentally changed or reinvented. After two and a half centuries, from ca. 525 to ca. 775, when there seems to have been no philosophizing, Latin Europe did not simply reassume, a little bleary eyed, its former philosophical existence. Indeed, it is even uncertain what that former existence would have been. Late ancient philosophy as practiced in the great Platonic schools of Athens and Alexandria? No; its links with medieval Latin thought, as opposed to Byzantine and Islamic thought, were partial and indirect. Ancient Latin philosophy? But that was hardly a tradition, just a handful of books and authors. Instead of envisaging a reawakening, then, it is more profitable to picture the emergence of a set of cultural circumstances utterly different from those of the ancient world, even once it had been christianized, and then to see in what way people began philosophizing within them. This is the aim of the first two parts of this chapter: the first outlines the places, institutional and intellectual, where philosophy took place from the late eighth to the twelfth century; the second looks at the ways in which thinkers thought philosophically within them – both externally, through written forms, and internally, through forms of argument. In the much briefer third part, I try to justify some of my choices – the way I have identified philosophy, and my marking out ca. 780 – ca. 1200 (for short: ‘the early Middle Ages’) as a discrete period in Latin philosophy.

The first unquestionably big idea in the history of philosophy was the idea of form. The idea of course belonged to Plato, and was then domesticated at the hands of Aristotle, who paired form with matter as the two chief principles of his metaphysics and natural philosophy. In the medieval period, it was Aristotle’s conception of form and matter that generally dominated. This was true for both the Islamic and the Christian tradition, once the entire Aristotelian corpus became available. For this reason, although there is much to say about the fate of Platonic Forms in medieval thought, the present chapter will focus on the Aristotelian tradition.

Aristotelian commentators have been puzzled by form and matter for as long as there have been Aristotelian commentators. Indeed, it would not be too much to say that these are topics about which Aristotelians have never formed a very clear conception, and that their failure to do so was the principal reason why Aristotelianism ceased to be a flourishing research program from the seventeenth century onward. For those who aspire to a modern revival of Aristotelianism, the concepts of form and matter can easily take on the aspect of a kind of Holy Grail, such that if only we could get these ideas clearly in focus, we could see our way forward on any number of philosophical fronts, such as the union of mind and body, the coherence and endurance of substances, the nature of causality, and so on.

In the Rules for the Direction of the Mind (Rule 12), René Descartes pokes fun at the Aristotelian definition of motion. “Who doesn’t know what motion is?,” he asks rhetorically; he then contends that motion has no need of an explanation, because each and every one of us knows what it is. In The World ch. 7, started around the same time, Descartes even claims that he finds the scholastic definition of motion so obscure that he is forced to leave it in “their language” – that is, motus est actus entis in potentia prout in potentia est (“motion is the actuality of a thing in potentiality insofar as it is in potentiality”). For Aristotle, however, and the medievals in his wake, motion was not merely an event familiar from everyday experience, but a phenomenon whose nature needed closer investigation. The central place that motion occupied in medieval thought can be understood only in the context of Aristotelian natural philosophy, particularly as it was set out in Book III of Aristotle’s Physics and developed by medieval thinkers.

This chapter will restrict itself to the medieval discussion of the nature of motion – that is, it will restrict itself to the question ‘What is motion?’ or, more generally, ‘What is change?’ Other significant problem areas which medieval thinkers addressed include the dynamic and kinematic aspects of motion – that is, motion’s relations to distance and time, and the causes of motion.

THE END OF PHILOSOPHY IN LATE ANTIQUITY AND THE REMNANTS OF GREEK THOUGHT

Philosophy died a lingering death before Islam appeared. The long demise started arguably with the reign of Diocletian (284–305), as the social, demographic, administrative, and other changes that would eventually lead to the end of the ancient world first set in; in consequence of these changes, philosophy – as the living practice of rational thinking about human beings and the universe outside socially instilled and institutionally sanctioned mythologies and superstitions – was seen to represent attitudes and habits of mind little appreciated and even less tolerated. After Justinian’s 529 edict prohibiting pagans to teach, whatever was left of the much attenuated academic practice of philosophy limped on for another two or three generations until, as the current interpretation of the evidence has it, the last philosopher in Alexandria, Stephanus, was invited by the Emperor Heraclius to Constantinople around 610. And that is the last we hear for some time of philosophy in Greek, for in the ensuing two centuries – during, that is, the Iconoclastic controversy in Byzantium and the so-called “Dark Ages” – philosophical treatises were not even copied, let alone composed. This situation continued until the Macedonian renaissance of the second half of the ninth century when there was, if not a resurrection of philosophy, at least renewed interest in philosophical literature apparently occasioned by the Graeco-Arabic translation movement in Baghdad. The interest manifested itself in the transcription of philosophical writings in new manuscript copies – an activity to which we owe the very survival of many an ancient text – and in the production of some logical scholia by men like Photius and Arethas.

Religious authority and the state were conceived very differently in the Byzantine world, the Muslim world, and Latin Europe. This last was the only civilization in which the age-old and nearly universal notion of sacred monarchy was consistently and increasingly challenged. In the Byzantine and Muslim worlds (except among the Shīʿites), the ruler remained a focal point of living religious authority. The Latin West was also distinguished by the variety of views expressed on this subject and the variety of forms which the relationship between church and state took. In some places the bishop was also temporal ruler, whereas in self-governing cities clergy had no overt political role. In feudal kingdoms, bishops were major landowners and often state counselors, but they owed their position partly to royal favor. Moreover, the way in which the church–state relationship was understood and theorized in the West changed as time went by. In Byzantium, by contrast, it never changed, while in the Muslim world, changes were rarely registered in what people wrote down.

BYZANTIUM

Eastern Christendom drew its notion of sacred monarchy from Roman imperial ideology, christianized by Eusebius of Caesarea (ca. 260–340). The one emperor was supposed to reflect the one God; he ruled “by God’s favor” as “God’s deputy.” The common form of address to a Byzantine emperor was “O most divine emperor.” For more than a thousand years, the Eastern church regarded the empire as an essential part of the expression of Christ in the world.

WAS THERE A PHYSICS BEFORE THE PHYSICS?

Was there anything like physics before the reception of the Aristotelian libri naturales? This question raises the problem of what kinds of discussions can be classified as “physical.” Modern scholars have commonly held that the beginnings of a scientific interest in natural phenomena among medieval authors appear only in the early twelfth century. The main characteristic of this development is said to be a shift of interest and consequently of method: whereas medieval scholars had previously interpreted nature symbolically, in correspondence with the practices of biblical exegesis, they henceforth focused on the inherent structure of physical reality, which they intended to understand and explain as such, which is to say secundum naturam or physicam.

While this approach to earlier medieval science has the advantage of having drawn scholarly interest toward the twelfth century, its weakness consists in its general neglect and global condemnation of the earlier stages of Latin thought. For it suggests that an interest in natural phenomena as such can hardly be discovered prior to the twelfth century, which would imply the (more or less complete) absence of natural philosophy during this time. However, if one takes the trouble to investigate the available sources, the actual situation turns out to be much more complicated and interesting. First, the sources on which early medieval authors draw already attest to the presence of a notion of physica.

In 1939 Raymond Klibansky published a programmatic essay entitled The Continuity of the Platonic Tradition during the Middle Ages, in which he presented a new project: the Corpus Platonicum Medii Aevi, meant as a counterpart of the Aristoteles Latinus. The term “continuity” in the title of the essay had a polemical intent: the principal aim of the planned collection of texts was, as it is stated in the Preface, “to reveal a neglected link” in the history of thought. In the study of medieval philosophy there existed a strong tendency to regard this period as an era dominated by Aristotelianism; it was not until the Renaissance that Plato would have been rediscovered. Against this prejudice Klibansky’s essay pointed to the continuity of the Platonic tradition throughout the Middle Ages. Medieval Platonism originated from two sources, a direct tradition, based on translations of Plato’s own works, and an indirect one through the intermediary of authors who transmitted essential doctrines of Platonism in their own accounts. This chapter will be focusing on the Latin Plato – a clear restriction, because, as Klibansky stresses, a full understanding of the role of Platonism in the Middle Ages has to take the Arabic tradition into account.

PLATO LATINUS

Boethius, one of the “founders of the Middle Ages,” saw it as his mission to make the treasures of philosophy accessible to the West. He tried to realize Cicero’s exhortation to transfer philosophy from the Greek to the Latin world and formulated to that end an ambitious program: he wanted to translate the complete works of Plato and Aristotle into Latin and to show the fundamental accordance between the two philosophers by commentaries on their works. But Boethius could only realize a fraction of this project, namely, translations of and commentaries on Aristotle’s logical works. During the entire Middle Ages the direct knowledge of Plato remained rather restricted.

The sources for what we know of medieval thinking on law and nature include the Church Fathers and scholastic theologians, as well as Roman legal writings, and the somewhat confused cluster of texts that were drawn together in the twelfth and thirteenth centuries to constitute a body of recognized “canon law” for academic study. Of the first importance here is Gratian’s Decretum from the 1140s, the ground-breaking manual of canon law on which many subsequent treatises and commentaries would rely. These sources show how the classical understanding of a right (ius) as the subjective right of an individual contrasts with the characteristically medieval understanding of ius as “a system of objectively right relationships.” Medieval discussions of these issues pass through a complex set of questions about law and human nature, until the point where thinkers begin to stand away from tradition and ask radical questions. This leads through early modern political thought to a conventionalism that says morality is a mere convention that depends on the interaction between individuals.

DEFINITIONS AND CONCEPTS: ‘LAW’ AND ‘NATURE’

For the clusters of concepts for which we use the modern English words ‘law’ and ‘nature,’ a series of Latin terms were used from the ancient world to the Middle Ages, often equivocally, and with a shifting range of meanings.

Much of the recent attention of historians of medieval logic has focused on medieval semantics. Just as prominent in medieval logical treatises, however, is the topic of inference, and a great deal of sophisticated work was done in this area, particularly by the fourteenth-century Latin authors on which this chapter will concentrate.

KINDS OF INFERENCE

Inferences are the building blocks of scholastic thought, and it is scarcely possible to read a paragraph of later medieval philosophy without encountering the terminology in which inferences are couched. Indeed, nothing is more familiar from scholastic texts than phrases such as this: Patet consequentia, antecedens est verum, ergo et consequens (‘The inference is seen to hold, the premise is true, so the conclusion is true too’). The term consequentia translates most readily as ‘inference,’ but what counts as an inference, to say nothing of what counts as a valid inference, is a thorny question. Even as good a logician as John Buridan may describe a consequentia as amolecular proposition (propositio hypothetica): “Now an inference is a molecular proposition, for it is composed from several propositions conjoined by the expression ‘if ‘ or by the expression ‘therefore’ or something similar” (Tract. de consequentiis I.3, ed. Hubien, p. 21). Yet when one argues: ‘This is false, Socrates utters it, so it follows that Socrates utters a falsehood,’ there is no conditional in this inference (consequentia), but two premises (antecedentia) and a conclusion (consequens). The same is true of syllogistic inference, in which there are two premises and a conclusion.

Medieval philosophers routinely distinguish between what is within the mind (in anima) and what is outside the mind (extra animam). Material substances and their qualities are taken to be paradigmatic cases of the latter, while emotions, acts of will, imaginations, and intellectual processes are salient examples of the former. An important array of problems these thinkers have to face, then, arise from the need to account for the various connections that can link the two realms. The most central of these problems is that some of the intramental stuff sometimes correctly represents the extramental: many of the philosophical preoccupations of the period, as it turns out, have to do with how knowledge comes about within the mind and how it is preserved.

The ultimate stake here is the human capacity for reaching truth. Following Aristotle, truth and falsity are thought of as features of propositions; and propositions, in Aristotelian logic, are taken to be complex units. Insofar, then, as the mental realm is the primary locus for knowledge, belief, and the like, there have to be propositions in it, and those have to be composed of simpler units: “for truth and falsity” Aristotle wrote, “involve a combination of thoughts” (De anima III.8, 432a10). Those subpropositional items, capable of serving as the basic representational units for the construction of mental propositions, will be the focus of the present chapter.

OCKHAM’s SEMANTIC INNOVATIONS

The most significant development in the history of late medieval philosophy and theology was the emergence of late medieval nominalism, eventually culminating in the quasi-institutional separation of the realist “old way” (via antiqua) and the nominalist “modern way” (via moderna). This chapter will confine itself to analyzing the fundamental changes in semantic theory initiated by William of Ockham, and brought to fruition by John Buridan. In order to be able to see the significance of these conceptual changes against the background of the older theory, the discussion begins with a brief sketch of those common characteristics of the “old semantics” that Ockham abandoned. After presenting Ockham’s main reasons for breaking with the older model and sketching his alternative ideas, the discussion proceeds to a more detailed analysis of Buridan’s radically new approach to constructing semantic theory.

The term ‘realism’ in connection with medieval philosophy is generally used to indicate a metaphysical position concerning universals, namely, the assumption of the existence of some abstract, universal entities expressed by our universal terms, such as ‘man’ or ‘animal.’ But medieval realism as a semantic conception is more than just a theory of universals; it is rather a comprehensive conception of the relationships between language, thought, and reality. The easiest way to introduce the basic ideas of this conception is through the analysis of a simple example. Consider the proposition ‘Every man is an animal.’

Illumination has an intriguingly complex history, which could be approached in many different ways. One could trace the philosophical evolution of the theme of light as a metaphor for understanding intellectual cognition, in which case our treatment would have to commence with the discussion of intellectual cognition among the major figures in Greek philosophy, especially Plato and Aristotle, both of whom regularly employed the metaphor of light in their efforts at grappling with the mysterious nature of intellectual cognition. Alternatively, one could focus on theories of human intellectual cognition that appeal to intellects higher than ours but still not divine to account for how human intellectual activities are possible. But the object of the present chapter, more narrowly still, is to trace out the theory of divine illumination – that is, the theory of how God’s light is required to account fully for how humans are capable of attaining the truth that they manage to attain through their intellectual activities. Considered in this way, the philosophical story we shall trace begins with Augustine, though the figures we shall be focused upon mainly are thirteenth-century philosophers. The reason for targeting thirteenth-century figures is that, although the texts of Augustine that inspire the theory were well known throughout the Middle Ages, it was only in the late twelfth and early thirteenth centuries that philosophers writing in Latin began to perceive, largely through their acquaintance with the recently translated Arabic sources and translations of Aristotle, that an alternative approach to that of Augustine was a genuinely viable option.