Unlike many thirteenth- and fourteenth-century authors, Scotus never wrote a grammar or logic handbook. Nor did he compose a treatise dealing explicitly with the grammatical and semantic issues that were eagerly debated at his time - for instance a treatise about the famous “properties of terms” or the “modes of signifying.” The only work concerning grammar and semantics, entitled Tractatus de modis significandi sive Grammatica speculativa, that was attributed to him until the beginning of the twentieth century, proved to be inauthentic; it was written by his contemporary Thomas of Erfurt, a leading representative of the school of the “modistae.” Given such an apparent lack of writings dedicated to grammatical and semantic problems, one may have the impression that Scotus was not particularly interested in linguistic analysis and that he should be regarded as a theologian, metaphysician, and moral philosopher, but not as a philosopher of language.

Yet such an impression would be quite misleading. Although Scotus never wrote a grammar or logic handbook, he had a keen interest in linguistic theory. This interest is most obvious in his commentaries on the Isagoge, on the Categories, and on Peri hermeneias. In these early writings, Scotus does not confine himself to paraphrasing Aristotle’s and Porphyry’s view. He rather uses their opinion as a starting point for a thorough discussion of fundamental issues in philosophical semantics – a discussion that allows him to critically examine various linguistic theories of his contemporaries and to develop his own theory. Such a discussion can also be found in some parts of his later works, especially in his metaphysical and theological writings.

The theory of natural law is the heart of the ethics of John Duns Scotus. Unlike other approaches in medieval ethics, Scotus’s framework is not that of an ethics of virtue. One reason for this is Scotus’s innovative concept of will, which diverges significantly from its classical and medieval predecessors. This new conception of will, and the assumptions for action theory that arise from it, require a different systematic role for the concept of virtue, one that accords greater weight to the judgment of reason than to the natural goal-directedness of purposive action. What takes center stage in Scotus’s ethics is the obligation on the part of reason to what is apprehended in the natural law as a practical truth, rather than what befits the agent’s end-directed nature as it is manifested in the virtues.

A second theme that determines the fundamental orientation of Scotus’s practical philosophy arises from the twofold task that confronted Scotus as a theologian. On the one hand, because of the influence of the Aristotelian conception of science, he had to show that the claim of theology to be a science could be made good. On the other hand, because he belonged to the Franciscan tradition, he also had to emphasize the practical character of theology. As a result, Scotus was faced with the task of developing an understanding of practical science that would show how both demands could be consistently met1 As I show in detail in this chapter, Scotus’s theory of natural law is precisely a response to this higher standard for rational acceptability.

By the end of the thirteenth century, it was clear that Aristotle’s physics and cosmology presented claims that were incompatible with God’s omnipotence. According to Scotus, “whatever does not evidently include a contradiction and from which a contradiction does not necessarily follow, is possible for God.” But many states of affairs, treated as impossible by Aristotle, seemed to involve no contradiction. Already in 1277, Stephen Tempier, Bishop of Paris, had issued his influential condemnation of, among other things, several key claims of Aristotle’s physics and cosmology precisely because they implied limitations on God’s absolute power. This condemnation did not lead to a wholesale rejection of Aristotelian thought, however. Aristotle had provided the most detailed and powerful conception of the physical universe known to medieval thinkers, and Scotus, like most of his contemporaries, was deeply wedded to this conception in its broad outlines and in a great deal of its detail. But he formed part of a movement, beginning in the late thirteenth century, and gathering momentum in the fourteenth, in which this conception was intensely scrutinized and modified in a number of fundamental respects. Nowhere did Aristotle’s thought pose greater problems than in doctrines concerning space and time. Scotus’s writings were an important chapter in the reexamination and modification of Aristotelian doctrines on these issues.

Work on Scotus’s moral psychology and action theory has been concerned almost exclusively with questions about the relationship between will and intellect and in particular about the freedom of the will itself. In this chapter I broaden the scope of inquiry. For I contend that Scotus’s views in moral psychology are best understood against the background of a long tradition of metaethical reflection on the relationship between being and goodness. In the first section of this chapter, therefore, I sketch the main lines of that tradition in medieval thinking and examine the novel and sometimes daring ways in which Scotus appropriated them. In the sections that follow I elaborate on three areas of Scotus’s action theory, very broadly conceived, in which his modifications of the medieval metaethical tradition can be seen bearing philosophical fruit. Thus, in the second section I examine his account of the goodness of moral acts, in the third his understanding of the passive dispositions of both sensitive appetite and will, and in the fourth his account of the active power of will.

This chapter discusses Scotus’s metaphysics under six headings: the nature of metaphysics itself as a discipline (Section I); identity and distinctness (Section II); the extent and scope of the Aristotelian categories (Section III); causality and essential orders (Section IV); matter, form, and the composite of matter and form (Section V); and a brief return to the nature of metaphysics (Section VI). Some metaphysical topics are not treated here but in other chapters of this volume: space and time (Chapter 2), universals and individuation (Chapter 3), and modality (Chapter 4). Scotus’s proof of God’s existence, discussed in Section IV, is examined in Chapter 6.

METAPHYSICS AS THE SCIENCE OF BEING

Theoretical Science

Scotus holds that there are exactly three real theoretical sciences, pursued for their own sake, that are open to us in our present life: metaphysics, mathematics, and physics (In Metaph. 6, q. 1, nn. 43–6). Each qualification is important. The requirement that such sciences be “real” – that is, concerned with things in the world rather than our concepts of them – excludes logic, which is the normative science of how we are to think about things, and thus concerned with concepts. The requirement that such sciences be pursued for their own sake excludes ethics, whose primary goal is to direct and regulate the will. The requirement that we can attain such knowledge in the condition of our present life, where we can only know things through sense perception and hence have no direct epistemic access to principles or to immaterial beings, rules out theology in the strict sense as well as a properly axiomatic metaphysics; we can however construct a ‘natural’ theology and metaphysics within our limitations. Mathematics and physics are defined in terms of material substance. Mathematics deals with material substances in their material aspect, namely, in terms of their purely quantitative features (which they have in virtue of their matter) and whatever is consequent upon those features.

Scotus’s teachings on moral virtue have attracted little attention, in part because there is no single text where he presents them systematically, in part because scholars tend to associate Scotus with the ethics of freedom and right reason. Even those sympathetic to his views report, with apparent regret, his move away from the virtue-centered Aristotelian model of ethics. This chapter attempts to explain the various roles that virtues do and do not play in his ethical theory. While Aristotle receives his share of criticism, so, too, does Augustine.

THIRTEENTH-CENTURY ETHICS: A LARGE, CONFUSING LEGACY

Ancient ethics takes as its starting point questions about the happiest human life and the virtues needed to live such a life. Virtues are thought to be dispositions developed only through many years of learning and practice, beginning in childhood. Vices, too, are dispositions; and like virtues, they gradually become “second nature” to the individual. For this reason Aristotle describes moral character as impossible, or at least exceedingly difficult, to change. His definition of moral virtue as a disposition concerned with choice does not imply, then, that people always remain free to choose actions “out of character.”

Both present-day historians of philosophy and those working in the past two centuries have considered the thought of Duns Scotus regarding the philosophical problems of universals and individuation as laying the groundwork for much of the philosophical speculation of the fourteenth and fifteenth centuries. Their judgment is well founded, being based on numerous texts in writers such as William of Ockham, Adam Wodeham, Walter Burley, and a host of others whose starting points in discussing both universals and individuation were often the views of Duns Scotus. Furthermore, as the problem of justifying and delimiting the range of natural knowledge became more and more central to philosophical as well as theological investigation, the influence of Duns Scotus on the two problems under discussion continued to grow. Realists as late as the sixteenth and seventeenth centuries looked to Scotus’s works for supporting arguments and conceptual tools whereby to salvage their claims that universals exist outside the mind, whereas the conceptualists and nominalists of later centuries often began their critique of contemporary opponents by pointing out the weaknesses in Scotus’s theories. The historical importance of Scotus’s thought on the subjects being considered here is then clear enough. But the systematic value of his solutions to the problems of universals and individuation should not be overlooked. Several contemporary philosophers working in the areas of metaphysics and epistemology appeal to distinctions bearing striking resemblances to those advanced by Scotus and his followers, especially regarding the problem of individuation.

The Earnest Professor begins the lecture by announcing that today we are going to investigate what we can know about God. The Artless Student immediately asks how it is possible that we finite minds can comprehend anything about the infinite. The Professor groans inwardly, resisting the temptation to retort by asking how the finite mind of the Student is so certain that God is infinite, given the Student’s avowal of doubt about the adequacy of finite minds.

Eager to maintain classroom civility, the Professor might congratulate the Student on fastening on a question discussed at length by John Duns Scotus. It is a sign of the seriousness with which Scotus takes this and related issues that he tackles them immediately in the Ordinatio version of his monumental Commentary on the Sentences of Peter Lombard. The title of the first question in the Prologue to the First Part is “Whether It Is Necessary for Man in His Present State to Be Supernaturally Inspired with Some Doctrine.” The title of the first question of the First Part of the Third Distinction is “Whether God Is Naturally Knowable to the Wayfarer’s Intellect.” God’s existence is not at stake in these questions. Scotus thinks that God’s existence can be established as an item of natural theology, that part of theological speculation that can be developed by reason alone, independent of any kind of revelation. Scotus takes himself to be in agreement with Aristotle that human sense experience and natural reason are adequate to provide a demonstration of God’s existence.

A study of human nature involves, first and foremost, a study of the human soul. The fact that we have a soul is not even a point of controversy, given the way Aquinas defines his terms. What is controversial is the nature of soul. The first and perhaps hardest article of the Treatise asks whether the soul is a body. Aquinas answers in the negative, but this does not rule out the soul's being something material, in our modern sense (§1.1). Aquinas is concerned with refuting the ancient natural philosophers, who thought that all things were bodies (§1.2). In opposition to their reductive account, Aquinas insists on the explanatory priority of actuality (§1.3). But his dispute with the ancients in fact rests on a deep metaphysical disagreement about the nature of matter, a disagreement that points toward the reductive nature of Aquinas's own account (§1.4).

What is a human being?

Aristotle remarks in Metaphysics VII 17 that the question What is a human being? is inherently obscure because it doesn't give us any help in breaking down the problem.

Aquinas's treatment of the senses is brief but interesting (§6.1). The senses, on his account, were designed by nature to detect certain features of the environment. In analyzing the senses he makes teleological assumptions, but not necessarily ones that we would find unacceptable (§6.2). His account begins with the objects of sensation and works toward a characterization of the capacities on which these objects make an impression. The function of the five external senses is defined in terms of the sensible qualities that they perceive: white, sweet, and so on (§6.3). But because animals need to do more than discriminate between different colors or different flavors, there must be further, internal sensory capacities, including a common sense that makes comparative and second-order judgments, but does not account for consciousness (§6.4).

Does Aquinas have a theory of sensation?

A cursory inspection of the Treatise reveals that Aquinas does not think it very important to consider the senses. These topics are covered in the space of two articles (78.3–4), only the first of which is devoted to what we count as the senses – namely, the five external senses (78.3). Even the seemingly uninteresting powers of the nutritive soul (the powers for nutrition, growth, and reproduction) receive an article's worth of attention (in 78.2). In contrast, the appetitive powers are the subject of four whole questions (QQ80–83), and the intellective capacity is the subject of the thirteen articles of Q79. Moreover, when Aquinas turns to the soul's operations, his entire attention turns out to be focused on the intellective and appetitive capacities. All of QQ84–89 is dedicated to the operations of intellect.

This book is a close study of Aquinas's best-known philosophical text (§In.1), read in the light of his full body of writings (§In.2). The topic is human nature, which for Aquinas means above all a discussion of the soul and its various capacities (§In.3). My focus is philosophical, and yet the subject is a work of theology, because often it is theology in the Middle Ages that comes closest to our modern philosophical concerns (§In.4). Still, it is crucial to understand the theological context. Aquinas's interest in the philosophical problems surrounding human nature grows out of his broader theological views about the meaning of life (§In.5).

Overview

In the chapters to come, I have some novel and perhaps surprising things to say about Thomas Aquinas. As I consider how best to ease the reader down this road, the words of Montaigne come to mind: “Aristotle wrote to be understood; if he could not do this, much less will another that is not so good at it” (Essays, ch. 21). In fact I doubt whether Aristotle always did write to be understood, but certainly Aquinas did, above all in his reader-friendly Summa theologiae. But in the more than 700 years that have passed since Aquinas's death in 1274, our modes of expression have changed a great deal. Surely there is some call for commentary.

Of course, I am not alone in this enterprise.

Beginning with Q84, the Treatise takes up the operations of the soul's various capacities. Aquinas officially confines his attention to intellectual operations (see §In.4), but the workings of intellect are not themselves intelligible apart from the workings of sense. Even in nonrational animals, there is something that comes close to the power of reason, the estimative power (§9.1). The human sensory system has something even more sophisticated, a cogitative power, which along with intellect plays a crucial role in human perception (§9.2). These perceptual processes furnish the information (phantasms) which the intellect runs on (§9.3). And even once the intellect receives this information, the sensory powers continue to play a role, because the intellect must constantly turn itself back toward phantasms, relying on the senses to furnish the images that human thinking constantly requires (§9.4).

Forms and intentions

Aquinas draws a sharp distinction between the sensory and the rational. The one is material, the other immaterial; the one apprehends particular features of the world, the other apprehends the world as universal. One might suppose, accordingly, that the operations of sense and intellect would be likewise segregated. In fact the opposite is true. The cognitive processes of a human being are in large part a cooperative venture between sense and intellect. To understand the operations of intellect, one must first understand the higher sensory operations.