Gyula Klima

This volume is about the most mind-boggling sacrament of the Christian faith, also referred to as the Sacrament of the Altar, the Eucharist: in its Roman Catholic interpretation, the conversion of the substance of the bread and wine into the body and blood of Christ for Holy Communion. The challenge of providing a rational interpretation of this doctrine of faith proved to be one of the most contentious issues in the Western history of ideas, apparently going against self-evident metaphysical principles (requiring accidents existing without a substance, and a body in several places at the same time, etc.), and dividing schools of thought, indeed, eventually, warring religious factions. The volume addresses both the metaphysical, theoretical issues involved in this challenge and the historical, theological developments of how meeting this challenge played out first in the schools and even later in religious schisms, leading to the paradigmatic shift from medieval to modern forms of thought. The essays of the volume derive from the lectures of an eponymous international conference held in Budapest, Hungary, which was also the occasion of founding the Society for the History of European Ideas (SEHI); accordingly, the book is the first volume of the annual Proceedings of the SEHI. This book is aimed just as much at laymen and religious scholars seeking a better understanding of their faith as at anyone seeking this understanding with a non-religious attitude.

This book provides the Latin text and its annotated English translation of the question-commentary of John Buridan (ca. 1300-1360) on Aristotle’s “On the Soul”. Buridan was the most influential Parisian nominalist philosopher of his time. His work speaks across centuries to our modern concerns in the philosophy of mind. This volume completes the project of a volume published earlier in the same series: “Questions on the Soul by John Buridan and Others”. An appealing book for scholars of Aristotle and those who are in the field of Medieval philosophy.

Under the traditional classification of medieval positions on the issue of universals, both Aquinas and Buridan would have to be deemed to be “conceptualists”: they both deny the existence of mind-independent, Platonic universals (against “realists”), and they both attribute universality primarily to the representative function of our universal concepts, and thus only secondarily to universal names of human languages (against “nominalists”). Yet, Aquinas is quite appropriately classified as a “moderate realist,” and Buridan as an “Ockhamist nominalist.” This paper will argue that what justifies these more refined classifications is the two authors’ radically different conceptions of the representative function of our universal concepts. The paper will show how this difference results in their opposing judgments concerning the demonstrability of the thesis of the immateriality of the human intellect and will reply to Buridan’s main objection to Aquinas’s argument for this thesis, by pointing out the objection’s conflation of merely indifferent, non-distinctive singular representation with genuinely universal intellectual representation. In its conclusion, the paper will briefly gesture at an important contemporary implication of Aquinas’s thesis concerning a metaphysical limitation of artificial intelligence.

This paper presents John Buridan’s nominalist ontology of habits, as the acquired qualities of innate powers aiding or hampering their operations, against the background of a more traditional interpretation of Aristotle’s doctrine to be found in Boethius, Albert the Great, Thomas Aquinas, and Cajetan. The paper argues that considerations of his late question commentary on Aristotle’s Nicomachean Ethics may have forced Buridan to rethink some of his earlier arguments for his parsimonious nominalist ontology of powers endorsed in such earlier works as his Questions on Aristotle’s Categories and De anima. The lesson to be drawn from this investigation seems to be that upon working out the details of a nominalist programme in such fields as moral psychology and ethics, the requisite refinements sooner or later will involve such modifications of an originally “radical” programme that would bring it closer to what used to be the “mainstream” view. Even so, this much seems enough further down the line to change significantly how issues are framed relative to the “mainstream” view as well.

An argument with roots in ancient Greek philosophy claims that only humans are capable of a certain class of thought termed conceptual, as opposed to perceptual thought, which is common to humans, the higher animals, and some machines. We outline the most detailed modern version of this argument due to Mortimer Adler, who in the 1960s argued for the uniqueness of the human power of conceptual thought. He also admitted that if conceptual thought were ever manifested by machines, such an achievement would contradict his conclusion. We revisit Adler’s criterion in the light of the past five decades of artificial-intelligence research, and refine it in view of the classical definitions of perceptual and conceptual thought. We then examine two well-publicized examples of creative works produced by AI systems and show that evidence for conceptual thought appears to be lacking in them. Although clearer evidence for conceptual thought on the part of AI systems may arise in the near future, especially if the global neuronal workspace theory of consciousness prevails over its rival, integrated information theory, the question of whether AI systems can engage in conceptual thought appears to be still open.

Common representational content allows the Buridanian classification of human concepts discussed in the fourth chapter, which provides the first thoroughgoing, systematic survey of Buridan’s conception of a mental language. The chapter discusses the divisions of concepts into syncategorematic and categorematic, simple and complex, absolute and connotative, and singular and common concepts. Besides presenting these classifications, the chapter provides a detailed discussion of the idea of conceptual complexity as semantic compositionality, its role in Buridan’s nominalist program of “ontological reduction,” and his precarious positioning of his account of the distinction between the representational contents of universal and singular concepts “somewhere between” those of Ockham and Aquinas. The discussion relates the emerging issues to contemporary concerns in the philosophy of mind and language, such as the possibility of forming genuinely singular concepts and simple substantial concepts that would allow some terms of our language to function as rigid designators; the differences between consciousness and mental content; and the problem of universal representation without real universals.

This chapter provides a brief survey of Buridan’s reliabilist epistemology, contrasting it with skeptical challenges of his time, and comparing it with modern responses to similar skeptical challenges in modern philosophy, arguably stemming from the controversies of Buridan’s time. In particular, the chapter argues that the sort of “Demon-skepticism” modern readers are familiar with from Descartes was made conceptually possible precisely by the emergence of late-medieval nominalist semantics, and that the modern strategies responding to the skeptical challenge, exemplified by the works of Thomas Reid and most recently John Greco, originate in the epistemic principles of Buridan.

The third chapter discusses how Buridan’s conception of mental language provides the grounding for the objectivity and universality of logic despite the radical conventionality of written and spoken languages. Buridan’s conception, since it is based on the Aristotelian idea of the uniformity of natural human capacities in all individual humans, is nothing like modern psychologism, the kind heavily criticized by Frege. Indeed, Buridan’s mental language is not a “private language” criticized by Wittgenstein. On Buridan’s conception, the naturally representative units of human mental language, namely, human concepts, are not inter-subjectively inaccessible private mental states; on the contrary, they are common to us all in our thinking. Of course, our concepts, being individual acts of individual minds are singular token-symbols, but they are common in their representational content: in what and how they represent for all humans. This is precisely the ground for their intersubjective accessibility as well as for the objectivity and universality of logic.

Having seen the limitations of a reconstruction of Buridan’s semantics in terms of a modified quantification theory, this chapter begins engaging Buridan’s theory in its own terms, starting with a detailed discussion of the semantic properties of terms. The discussion moves from a brief discussion of Buridan’s distinction between immediate and ultimate signification, to Buridan’s theory of reference, namely, supposition, and oblique reference, namely, appellation. The chapter discusses suppositional descents as distinguishing quantifier-scopes, numerical quantification, and appellation in temporal and modal contexts, as well as Buridan’s peculiar theory of appellatio rationis, the theory of oblique reference to concepts in intentional contexts.

The fifth chapter provides a detailed discussion of Buridan’s strategy of identifying the conceptual structures discussed in the chapter 4 by means of the various “syntactical clues” provided by spoken and written natural languages. The chapter compares the Buridanian strategy of “regimentation” with the modern strategy of formalization, and argues that for the purposes of a “natural logic” the former is not inferior to the latter. But in order to bridge the conceptual gap between the two approaches, the chapter also discusses a simple extension of standard quantification theory that is capable of faithfully representing a large part of Buridan’s logic. Indeed, the chapter argues that the resulting formal system is in accord not only with Buridan’s logic, but with our natural language intuitions in general, providing more faithful representation of natural language reasoning than standard quantification theory.

This chapter continues the discussion of the issues raised by the chapter 6, focusing on the issue of ontological commitment. The chapter argues that Buridan’s theory of ampliation, reconstructed in terms of quantification with restricted variables, provides a genuine third alternative to the opposing modern views of Quine and “the Meinongians.” Furthermore, the chapter argues that Buridan’s theory thus reconstructed says “all the right things” according to Quine in its object-language; however, it still seems to side with the Meinongians in its meta-language. However, this is just a feature of the reconstruction: “the real Buridan” does not have this distinction, but works out his natural language semantics under conditions of what Tarski described as “semantic closure.”

This chapter provides a comprehensive survey of Buridan’s conception of logical validity in a semantically closed token-based system, as he conceives of natural languages. The chapter argues first that Buridan has very good logical, as well as merely metaphysical, reasons to conceive of natural languages as compositional systems of significative token-symbols. Next, the chapter discusses the peculiar Buridanian conception truth and validity, according to which validity must not be based on truth, and truth need not always follow upon correspondence. These results are presented as the consequences of Buridan’s pursuit of a consistently nominalist semantics for natural languages, able to handle the Liar Paradox and its kin involving reflective uses of language without the Tarskian distinction between object-language and meta-language, rejected for systematic reasons in the seventh chapter.

The sixth chapter discusses the issue of how the reconstruction of the relevant parts of Buridan’s logic and medieval logic in general, using restricted variables, validates the attribution of existential import to affirmative propositions, in turn establishing the validity of all relations of the traditional Square of Opposition. The chapter also discusses how Buridan’s theory of natural supposition handles some objections to this conception concerning law-like statements, and, in general, how his theory of ampliation handles the issue of existential import in intensional contexts.

This collection of readings with extensive editorial commentary brings together key texts of the most influential philosophers of the medieval era to provide a comprehensive introduction for students of philosophy. Features the writings of Augustine, Thomas Aquinas, Boethius, John Duns Scotus and other leading medieval thinkers Features several new translations of key thinkers of the medieval era, including John Buridan and Averroes Readings are accompanied by expert commentary from the editors, who are leading scholars in the field

The first chapter presents a brief summary of the little we know about Buridan’s life, and the somewhat more we know about his immediate historical influence. But this brief survey of known facts only sets up the main argument of the chapter intending to show Buridan’s “modernity” in more than one sense of the word. Buridan is “modern” in the medieval sense, being “the great architect” of what would become in late-medieval philosophy the nominalist via moderna, but he is also “modern” from our perspective, having many of the same concerns as contemporary analytic philosophers. Indeed, his philosophy can be the best key to understanding the major paradigm shifts between medieval and modern philosophy.

The second chapter spells out Buridan’s conception of logic as a practical science, teaching us, as logica docens, to heed the valid rules of reasoning embedded in our logical practice, logica utens. The chapter also deals with the particular difficulties of Buridan’s approach, considering his idea of the radical conventionality of written and spoken languages, consisting of token-symbols that owe their meaningfulness to the natural representational system of the human mind. This is the fundamental idea that naturally leads to the nominalist conception of a mental language. On this conception, mental language itself is a compositional semantic system of naturally representative token-symbols, the singular mental acts of singular human minds.