Gyula Klima

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.

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.

The final chapter provides a summary account of Buridan’s essentialist nominalism, showing how Buridan can successfully claim to be both a nominalist denying the existence of real shared essences and an essentialist endorsing the possibility of discovering truly essential attributes of things, which allows valid scientific generalizations. The concluding critical part of the chapter, however, points out a fundamental conflict between Buridan’s abstractionist cognitive psychology of absolute concepts and his logical semantics of the corresponding absolute terms that grounds his nominalist essentialism.

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.

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.”

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 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.

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 compares the modern reliabilist strategies, including Buridan’s antiskepticism, considered in the previous chapter with a premodern form of antiskepticism, exemplified by Aquinas’s doctrine of “the formal unity of the knower and the known”, which, as the chapter argues, simply does not allow the emergence of “Demon-skepticism.” In fact, the chapter further argues that the emergence of “Demon-skepticism“ in its most extreme form, allowing an impossibility to appear as a possibility, indicates a serious flaw in the nominalist conception of mental representation. Nevertheless, the chapter further argues that this flaw is easily masked by the apparent success of Buridan’s reliabilist strategy, not requiring the elimination of Demon-skepticism, but rather presenting reasonable ways for us to learn to live with it.

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.

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.