John Buridan’s approach to philosophy was profoundly shaped by the institutional setting in which he worked as well as by the explicitly pedagogical aim of his activities as an arts master and teacher of undergraduate students. He was not unique in this regard, as the medieval university and its teaching practices were well established by the fourteenth century. But there are a number of things about his career that are unusual.

First, he remained for his entire career in the Faculty of Arts at the University of Paris, apparently without ever moving on to seek an advanced, doctoral degree in theology, which was the career path taken by other well-known philosophers of the time such as William of Ockham, Walter Burley, and Nicole Oresme. It was probably a deliberate choice on Buridan’s part, but why this is we are not sure.¹ What it meant in practical terms is that he would have been responsible for teaching logic and the texts of Aristotle that constituted the arts curriculum (e.g., Physics, De anima, Metaphysics, Nicomachean Ethics) to undergraduates from his own Picard Nation. As a result, Buridan’s literary remains are mostly in the form of commentaries on Aristotle – line-by-line commentaries that explain the literal meaning of the text and question commentaries that explore its deeper, philosophical significance – both of which originated in the lecture hall.² He also wrote one of the most influential logic textbooks of the medieval period, the Summulae de dialectica (Compendium of Dialectic), a comprehensive treatment of the topics in logic and semantics that were taught in the schools at the time.³ Buridan’s commentaries and textbooks are without exception models of clarity, sound exegesis, and careful argumentation. Copies soon found their way to other, newer universities in northern Italy and eastern Europe, where they served as prototypes for other masters teaching the arts curriculum. As a result, Buridan continued to influence the way philosophy was taught well into the early modern period.

Besides determining the philosophical genres in which he worked, Buridan’s decision to remain an arts master meant that he had to be sensitive to the curricular mandates of the other faculties at Paris, especially the faculty of theology. Relations between the two faculties had become fraught in the latter half of the thirteenth century, culminating in the Condemnation of 1277, in which the Bishop of Paris declared certain Aristotelian propositions defended by certain arts masters to be inconsistent with revealed truth.⁴ The Condemnation cast a long shadow on later medieval philosophy, though it did not succeed in silencing philosophical discussion of ultimate questions about God and human nature. Buridan himself is circumspect in his approach to the relation between philosophy and theology: while conceding pride of place to theology, he at the same time establishes a domain for philosophy to operate independently, approximating what we might today think of as the secular realm. He says that theology takes precedence over metaphysics, the highest form of philosophy, but theology properly concerns what follows from church decretals and articles of faith, that is, from truths that are believed quite apart from the evidence we have for them.⁵ But if we “leave the faith aside [fide circumscripta],” metaphysics stands as the preeminent form of human wisdom and ordering principle (ordinatrix) of all the other sciences, including everything taught in the other faculties. So why does philosophy belong to the “lowest” faculty, the faculty of arts, where undergraduates are educated? Buridan jokes that the low regard for arts and “artists [artistae]” might be due to “the wealth of those who profess in the other faculties,” or perhaps to the fact that its curriculum includes the common or primary subjects of grammar, logic, and rhetoric. But along with such “trivial” arts, he reminds us that his faculty also teaches (1) natural philosophy, giving it precedence over medicine; (2) moral philosophy, giving it precedence over law; and (3) metaphysics, giving it precedence over all other forms of inquiry save revealed theology,⁶ which Buridan regards as kind of wisdom (sapientia) but not knowledge (scientia), a term he reserves for what can be rationally demonstrated on the basis of sense, memory, and experience. Given the Condemnation of 1277 and other institutional efforts by church authorities to limit the autonomy of philosophy in medieval universities, this is a remarkable thing to say.⁷

When philosophical inquiry is understood in this way, it creates a space, distinct from revealed theology, where philosophy (or, more properly, metaphysics) can address questions “about God and divinity.” The boundary is clear – “metaphysics considers only what can be proved and concluded deductively or inductively using demonstrative reason”⁸ – but it enables Buridan to consider everything from the divine attributes (omnipotence, eternality, freedom) to the providential structure of creation and the relation between human happiness and final beatitude, all from a human, creaturely perspective.⁹ Typically, he does not explicate matters of doctrine or challenge what the theologians say about God, but rather uses theological considerations to define the limits of philosophical inquiry. Thus, he famously defends the reliability of human empirical knowledge against his Parisian contemporary, Nicholas of Autrecourt, who used the doctrine of divine omnipotence to undermine confidence in the accepted Aristotelian accounts of perceptual, causal, and inductive knowledge. Buridan’s reply charges Autrecourt with an ignoratio elenchi, agreeing with Autrecourt that it follows from divine omnipotence that God could always deceive us in ways we could never detect, but denying that this is relevant to the justification of empirical knowledge, which is grounded in a posteriori considerations such as rational judgment and the evidence of sense, memory, and experience. Besides confirming the mandate of arts masters to teach philosophy via Aristotelian texts, this pointed the way to a definitive sphere of operations for philosophers, independent of revealed theology.

The second way in which Buridan was different was that he remained a secular master for his entire career rather than joining a religious order such as the Dominicans or Franciscans. Moving on to a higher faculty would have been natural enough for someone licensed to teach in the faculty of arts, since mendicant orders taught undergraduate novices at their own custodial schools, sending them to university only for graduate study. But in the larger context of fourteenth-century philosophy, this meant that Buridan was able to develop his views independently of the respective authorities invoked by the Dominican and Franciscan traditions, which were frequently in conflict. Thus, he was under no obligation, fraternal or otherwise, to defend the teachings of Thomas Aquinas on the Dominican side or those of Duns Scotus on the Franciscan side. What he does instead is help himself to insights and arguments from both sides, as needed, to develop his own positions. For example, he follows Thomas Aquinas in defending an intellectualist account of human free choice, arguing that whenever it chooses, the will is always motivated by reasons under the aspect of goodness. But he leavens this with the voluntarist consideration that as long as reason is not 100 percent certain about the best course of action, the will remains free not to accept it but rather to defer its choice in order to reflect on the matter further:¹⁰

This is not, to be sure, the same as the Scotistic idea that the will is an autonomous power able to transcend our natural and rational inclinations; Buridan clearly understands the will as a manifestation of our rational nature, not as a power belonging to an order distinct from it. Still, it represents a significant modification of the intellectualist position because it grants the will autonomy over the intellect in a very wide range of practical cases, where free choice is exercised in the absence of decisive reasons.¹¹ Buridan is thereby able to respond to Article 169 of the Condemnation of 1277, which had criticized the view (held by Aquinas, among others) that the will cannot knowingly act against reason, by reminding us of the uncertainty of moral life and making a virtue of the will’s ability to defer its acceptance or rejection of reason’s dictates.¹²

We see a similar effort to harmonize opposing views in the case of Buridan’s account of the cognition of singular objects. Duns Scotus had introduced the idea that not all human cognition occurs via a species or representative likeness abstracted from an object, which is the Aristotelian position defended by Thomas Aquinas; rather, there is a mode of cognition that is ‘intuitive’ in the sense that it provides an unmediated awareness of the existence of its object.¹³ The motivation for the doctrine was theological insofar as Scotus thought that such direct awareness would be the mode of cognition enjoyed in beatitude, when we finally see God face to face, no longer “through a glass darkly” (1 Cor. 13:12), and, furthermore, that if beatitude is our natural end, the power of intuitive cognition ought to be present among our intellectual and sensory powers in this life.¹⁴ Buridan accepts the doctrine, but he does not argue for it theologically, like Scotus, for the simple reason that as an arts master he was not permitted to address theological topics. What he does instead is provide an entirely secular account of the same idea, in terms of our ability to cognize an object as it exists before us, “in our prospect [in prospectu].” In this mode of cognition, he says, “things are perceived and judged to exist in the way they are perceived as existing in the prospect of the person cognizing them,” such that our judgment that a singular entity exists “could not be proven more evidently than by the fact that it appears in the prospect of sense,” that is, “just as you are present to me.”¹⁵ This is the basis for all singular cognition according to Buridan. It is the initial presentation of an object to the cognizing agent with its attributes “confused [confusa],” or fused together in their natural and unabstracted form. The same object may be further discriminated by the intellect as a singular of a certain type, or as representing a universal or common nature, but this requires the further act of abstracting a species from the initial presentation. Accordingly, the difference between divine and human cognition is that we lack the ability to understand everything there is to know about an object from its mere presence before us, whereas “God himself cognizes everything most distinctly and determinately, as it were in a singular manner, because he has everything per se perfectly in his prospect.”¹⁶

Buridan is not so accommodating of views he disagrees with, of course, and in cases of conflict, he usually defends what he takes to be the simplest account of the phenomenon at hand. Thus, he famously rejects the theory that propositions have their own significates, known as complexe significabilia, which serve as the proper object of scientific knowledge – a view originally developed by the Franciscan theologian Adam Wodeham, but which Buridan encountered in a slightly different version defended by the Augustinian theologian Gregory of Rimini in his Sentences commentary delivered at Paris in the early 1340s.¹⁷ In his refutation of Gregory’s view, Buridan is adamant that no explanatory advantage is to be gained by positing an additional semantic layer of sentence-meanings beyond categorematic terms and the things they signify; therefore, we may dispose of them with the razor:¹⁸

Throughout his writings, Buridan’s philosophical voice as an arts master, working within the curricular parameters of his faculty and engaging in theological questions only when they have secular consequences, remains consistent, clear, and distinctive.

In recent decades, we have learned more about Buridan’s contemporary influences and about the intellectual milieu of mid-fourteenth-century Paris.¹⁹ This has enabled us to correct mistakes in earlier histories of the period, such as Pierre Duhem’s notion that there was a “school of Buridan” at Paris consisting of Albert of Saxony, Themon Judeus, Nicole Oresme, and Marsilius of Inghen, all of whom Duhem claimed “faithfully received and developed his teachings.” We now know that despite being at the University of Paris around the same time, these thinkers had significantly different views on a number of questions (an unsurprising fact given that they were philosophers) and, in any case, were segregated institutionally because they belonged to different nations at the university.²⁰ This does not mean that they were not familiar with each other’s views, of course, just that the similarities Duhem noticed proved to be largely superficial. Among earlier authors, Buridan certainly had access to the Summa logicae of William of Ockham, though he never mentions Ockham by name, and his own Summulae de dialectica, while certainly following the nominalist via moderna inaugurated by Ockham, frames its teachings more traditionally in terms of the logic curriculum presented in the Summulae logicales of Peter of Spain.²¹ Likewise, Book i, q. 8, of Buridan’s Physics commentary makes Buridan’s opposition to the Ockhamist denial of quantitative forms explicit, but there are almost certainly other authors in the mix whose arguments Buridan is targeting, such as those of his Parisian contemporary, Albert of Saxony.²² Getting the full dialectical picture will require closer study of more sources. Another author influencing Buridan’s natural philosophy is the English logician Walter Burley, who is mentioned by name on several occasions. Buridan seems to have become acquainted with the controversy on the intension and remission of forms via Burley’s Tractatus primus and De intensione et remissione, though his own treatment of the problem in his commentaries on the Physics and On Generation and Corruption is probably aimed at another Parisian contemporary, Nicole Oresme, who defended a modified version of Burley’s position.²³ There are also cases where the influence comes from an unexpected quarter. The Nicomachean Ethics commentary of Gerald of Odo, a Franciscan theologian and opponent of Ockham who eventually became Minister General of the Order, is clearly a source text for Buridan’s own lengthy commentary on Aristotle’s Nicomachean Ethics, his longest work by far other than the Summulae de dialectica.²⁴ Buridan’s Nicomachean Ethics commentary is also noteworthy for the extensive use it makes of an ancient authority, Seneca, whose Stoic teachings he interprets not as opposed to Aristotelian moral philosophy but as perfective of it.²⁵

Among medieval authorities named by Buridan are Albertus Magnus, Thomas Aquinas (“Beatus Thomas,” as Aquinas was canonized in 1323), Giles of Rome, and Robert Grosseteste (“Lincolniensis”). He is also familiar with the writings of Roger Bacon on the propagation of species through a medium, and of John Pecham on perspectivism, though he does not mention either by name – typically, the arguments of lesser-known figures are prefaced by the formulaic aliqui dicunt (= some say) or, in the case of Pecham, by perspectivi dicunt.²⁶ Scholars have been able to identify possible opponents for two of Buridan’s early treatises: On Dependence, Agreement, and Difference (c. 1332) is directed against the realist theory of a certain “Picardus” or Picard master, thought to be Egidius of Feno (Buridan’s other opponent in the treatise – an “Anglicus” or arts master from the English-German Nation – is not known),²⁷ whereas the Question on Points (c. 1335) is very likely replying to Michael of Montecalario, a master from the French Nation whose Determinatio de puncto attacked Buridan’s views on indivisibles and the composition of continuous magnitudes.²⁸ As always, Buridan’s discussions point to a rich tapestry of philosophical debate occurring in the background, most of which, again, awaits discovery by scholars.

1.1 Works

As mentioned above, Buridan primarily wrote philosophical commentaries on Aristotle’s works, which formed the basis of the arts curriculum in fourteenth-century Paris. Most of these were developed as lecture courses in which Buridan offered his undergraduate students a close reading of the meaning of the text in the first part of his lecture, followed by a more detailed discussion of its philosophical implications in the second part, where he would also develop his own interpretations and refute others. The former survive in the genre of expositiones or literal commentaries and the latter as quaestiones, which are commentaries organized around a series of questions or problems raised by the text. Many of these questions were standardized and routinely addressed by other masters lecturing on the same text, such as the question of whether the human intellect is able to understand itself, which Buridan considers in Book iii, q. 9 of his commentary on Aristotle’s De anima.²⁹ His answer is that the intellect can indeed understand itself, but only discursively, in the course of thinking about other things, and not a priori and through its essence, like God.³⁰

Buridan frequently lectured more than once on a text; for example, his De anima commentary describes itself as his “third or final set of lectures [tertiam sive ultima lectura]” on De anima. We have hardly any surviving manuscripts of the first two versions, but the third version exists in over twenty manuscripts scattered across European libraries. This suggests that the relation between earlier and later versions was one of replacement rather than succession, with the final version offering the most settled or complete rendition of Buridan’s teaching.³¹ Like all good teachers, Buridan sometimes reuses the same material in different contexts when that is pedagogically appropriate. Thus, his lengthy discussion of how we cognize universals vs. singulars in Book iii, q. 8 of his De anima commentary is reprised in Book i, q. 7 of his Physics commentary, which was probably composed slightly later.³² It is possible to date Buridan’s works relative to each other through internal references, so we can sometimes infer their possible ordering. There are also occasional references to datable events such as the 1347 Condemnation of John of Mirecourt mentioned in Book iii, q. 11 of the final version of Buridan’s De anima commentary, giving us a terminus a quo for this work (assuming the reference is not a later interpolation). But for the most part, our grasp of the chronology of his writings is fairly speculative.³³