This presentation traces an historical root of the reductio ad absurdum mode of argumentation in Greek philosophy. I propose a new understanding of the liar paradox as an instance of this mode of argumentation. I show that the paradox was crea ted as part of a refutational argument in the controversy over the justification of realism and the realists concepts of truth and certainty. The paradox was part of the dialectical style of Greek scepticism, which was characterized, inter alia, by (...) the u se of the reductio ad absurdum. The paradox turns out to be a metaphysical and epistemological argument. (shrink)

Inference versus consequence , an invited lecture at the LOGICA 1997 conference at Castle Liblice, was part of a series of articles for which I did research during a Stockholm sabbatical in the autumn of 1995. The article seems to have been fairly effective in getting its point across and addresses a topic highly germane to the Uppsala workshop. Owing to its appearance in the LOGICA Yearbook 1997 , Filosofia Publishers, Prague, 1998, it has been rather inaccessible. Accordingly it is (...) republished here with only bibliographical changes and an afterword. (shrink)

Seguindo de perto a caracterização que Robert Blanché faz da lógica dos modernos em seu livro História da Lógica de Aristóteles a Bertrand Russell, pretendo mostrar como as Regulae de Descartes instanciam paradigmaticamente algumas das principais características das lógicas reformadas, típicas desse momento histórico. O próprio Blanché oferece vários exemplos do pertencimento de Descartes a esse contexto. De minha parte, pretendo contribuir com a discussão realizando um exame mais detalhado da parte final da Regra X, na qual desponta, já nesta (...) que é uma das primeiras obras de Descartes, certa noção de atividade mental, que está em relação tanto com as críticas cartesianas às matemáticas, no Discurso do Método, quanto com o argumento do cogito, nas Meditações. (shrink)

We present a set-theoretic model of the mental representation of classically quantified sentences (All P are Q, Some P are Q, Some P are not Q, and No P are Q). We take inclusion, exclusion, and their negations to be primitive concepts. We show that although these sentences are known to have a diagrammatic expres- sion (in the form of the Gergonne circles) that constitutes a semantic representation, these concepts can also be expressed syntactically in the form of algebraic formulas. (...) We hypothesized that the quantified sen- tences have an abstract underlying representation common to the formulas and their associated sets of dia- grams (models). We derived 9 predictions (3 semantic, 2 pragmatic, and 4 mixed) regarding people’s as- sessment of how well each of the 5 diagrams expresses the meaning of each of the quantified sentences. We report the results from 3 experiments using Gergonne’s (1817) circles or an adaptation of Leibniz (1903/ 1988) lines as external representations and show them to support the predictions. (shrink)

Jan Lukasiewicz's treatise on Aristotle's Syllogistic, published in the 1950s, has been very influential in framing contemporary understanding of Aristotle's logical systems. However, Lukasiewicz's interpretation is based on a number of tendentious claims, not least, the claim that the syllogistic was intended to apply only to non-empty terms. I show that this interpretation is not true to Aristotle's text and that a more coherent and faithful interpretation admits empty terms while maintaining all the relations of the traditional square of opposition.

The traditional definition per genus et differentiam is argued to be cognitively grounded in perception and in order to avoid needless argument, definitions are stipulated to assert boundaries. An analysis of the notion of perspective shows that a boundary is a composite of two distinctions: similarity that includes and difference that excludes. The concept is applied to the type-token distinction and percepts are shown to be the result of a comparison between a token as representing some phenomenon and a type (...) as representing the kind of object the phenomenon might be. The Principle of Connection is proposed as the mental architecture that gives rise to percepts. The value of a percept is shown to be one of Identical, Similar, Different or Contrary and its perceptual aspects represent the cognitive schema of Essence, Quality, Quantity and Relation. The two notions of similarity and difference are claimed to constitute the necessary and sufficient conditions for definitions. Accordingly, the qualitative elements of a definition signify the genus as representing the similarity of the defined entity in terms of others of its kind and the quantitative elements signify the differentia as representing the difference it has from everything else. Paying proper attention to both qualitative and quantitative aspects will enable formulation of definitions that are ‘good’. (shrink)

This is a critical examination of Antoine Arnauld's Logic or the Art of Thinking (1662), commonly known as the Port-Royal Logic. Rather than reading this work from the viewpoint of post-Fregean formal logic or the viewpoint of seventeenth-century intellectual history, I approach it with the aim of exploring its relationship to that contemporary field which may be labeled informal logic and/or argumentation theory. It turns out that the Port-Royal Logic is a precursor of this current field, or conversely, that this (...) field may be said to be in the same tradition. (shrink)

The taxonomy and analysis of fallacies in Aristotle's Sophistical Refutations pre-date the formal logic of his Prior Analytics A4-6. Of the 64 fully described examples of ?sophistical refutations? which are fallacious because they are only apparently valid, 49 have the wrong number of premisses or the wrong form of premiss or conclusion for analysis by the Prior Analytics theory of the categorical syllogism. The rest Aristotle either frames so that they do not look like categorical syllogisms or analyses in a (...) quite different way than by categorical syllogistic. (shrink)

What is logical relevance? Anderson and Belnap say that the “modern classical tradition [,] stemming from Frege and Whitehead-Russell, gave no consideration whatsoever to the classical notion of relevance.” But just what is this classical notion? I argue that the relevance tradition is implicitly most deeply concerned with the containment of truth-grounds, less deeply with the containment of classes, and least of all with variable sharing in the Anderson–Belnap manner. Thus modern classical logicians such as Peirce, Frege, Russell, Wittgenstein, and (...) Quine are implicit relevantists on the deepest level. In showing this, I reunite two fields of logic which, strangely from the traditional point of view, have become basically separated from each other: relevance logic and diagram logic. I argue that there are two main concepts of relevance, intensional and extensional. The first is that of the relevantists, who overlook the presence of the second in modern classical logic. The second is the concept of truth-ground containment as following from in Wittgenstein’s Tractatus. I show that this second concept belongs to the diagram tradition of showing that the premisses contain the conclusion by the fact that the conclusion is diagrammed in the very act of diagramming the premisses. I argue that the extensional concept is primary, with at least five usable modern classical filters or constraints and indefinitely many secondary intensional filters or constraints. For the extensional concept is the genus of deductive relevance, and the filters define species. Also following the Tractatus, deductive relevance, or full truth-ground containment, is the limit of inductive relevance, or partial truth-ground containment. Purely extensional inductive or partial relevance has its filters or species too. Thus extensional relevance is more properly a universal concept of relevance or summum genus with modern classical deductive logic, relevantist deductive logic, and inductive logic as its three main domains. (shrink)

This paper describes Peirce's systems of logic diagrams, focusing on the so-called ''existential'' graphs, which are equivalent to the first-order predicate calculus. It analyses their implications for the nature of mental representations, particularly mental models with which they have many characteristics in common. The graphs are intended to be iconic, i.e., to have a structure analogous to the structure of what they represent. They have emergent logical consequences and a single graph can capture all the different ways in which a (...) possibility can occur. Mental models share these properties. But, as the graphs show, certain aspects of propositions cannot be represented in an iconic or visualisable way. They include negation, and the representation of possibilities qua possibilities, which both require representations that do not depend on a perceptual modality. Peirce took his graphs to reveal the fundamental operations of reasoning, and the paper concludes with an analysis of different hypotheses about these operations. (shrink)

Inference is elementary and ubiquitous: Cognition always goes beyond the data. Thinking—including problem solving, decision making, judgement, planning, and argumentation—is here defined as the deliberate application and coordination of one's inferences to serve one's purposes. Reasoning, in turn, is epistemologically self-constrained thinking in which the application and coordination of inferences is guided by a metacognitive commitment to what are deemed to be justifiable inferential norms. The construction of rationality, in this view, involves increasing consciousness and control of logical and other (...) inferences. This metacognitive conception of rationality begins with logic rather than ending with it, and allows for developmental progress without positing a state of maturity. (shrink)

The language of the propositional calculus is extended by two families of propositional probability operators, inductively applicable to the formulae, and the set of all formulae provable in an arbitrary superintuitionistic propositional logic is extended by the probability measure axioms concerning those probability operators. A logical system obtained in such a way, similar to a kind of polymodal logic, makes possible to express a probability measure of truthfulness of any formula. The paper contains a description of the Kripke-type possible worlds (...) semantics covering the considered logical systems, being followed by the corresponding completeness results. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Whose Aristotle? Which Aristotelianism? A Historical Prolegomenon to Thomas Farrell’s Norms of Rhetorical CultureCarol PosterThe description of various works of logical and rhetorical theory as “Aristotelian,” although far from unusual, is not particularly informative, because it assumes, incorrectly, that there is some ultimate singular Aristotle being imitated by all authors who consider themselves, or who are labeled by others, Aristotelian. In fact, there never has been an interpretation of (...) Aristotle that satisfies the canon of St. Vincent of Lerins, “quod ubique, quod semper, quod ab omnibus creditum est”; instead, there have been almost as many Aristotles as there have been interpreters of Aristotle. Thomas Farrell’s Norms of Rhetorical Culture (1993), therefore, is not so much situated against the background of some single, unique, undisputed Aristotle but, rather, as he himself mentions, within an evolving tradition of Aristotelianism.The historical transformations of Aristotle include two distinct traditions, one oriented toward scientific-technical philosophy andthe other toward rhetorical-poetic and ethical humanism.1 The technical-philosophccical tradition, in which Aristotle was conceived primarily [End Page 375] as metaphysician and natural philosopher, emphasized the logical treatises of the organon, the speculative systems of the Physics and Metaphysics, and the scientific works of the biological treatises. This tradition originated in the Greco-Roman middle and Neoplatonic schools and has had a continuous history stretching through the Middle Ages, Counterreformation, neo-Thomism, and certain contemporary European postmodernisms. The rhetoricalhumanistic tradition, on the other hand, emphasizing the Rhetoric, Poetics, Politics, and ethical treatises, views Aristotle as a practical philosopher, concerned with the productive arts and those matters about which knowledge is probable rather than certain. This rhetorical-humanistic tradition was a relatively negligible aspect of Aristotle’s ancient reception, had a slight presence in the Islamic and Latin traditions, developed in certain strands of Renaissance humanism, and came to fruition in the late eighteenth century, primarily, though not exclusively, within a Protestant tradition. In eighteenth-and early nineteenth-century Britain, the rhetorical-humanistic Aristotle found expression directly in neoclassical poetics and, in a more complicated fashion, in a group of authors (including the Scottish moderates and the slightly later Oxford Noetics) who enlisted Aristotle in a battle against skepticism and materialism. It is the latter of the two strands of the rhetorical-humanistic Aristotle that resurfaces (albeit in an indirect and mediated fashion) in the work of Alastair MacIntyre, Richard McKeon (and other members of the Chicago school), and Thomas Farrell, who used Aristotle’s model of probable deliberation and habituated virtue to construct an alternative to twentieth-century skepticism and materialism.Significant Strata of Aristotelian ReceptionThe history of Aristotelian reception is not monolithic. There has been tremendous variation across periods and national traditions of what works were considered authentically Aristotelian, which of those works were considered important, and how they were interpreted. The phases of Aristotelian reception immediately relevant to Farrell’s work include Greco-Roman Platonism, Islamic commentary, medieval Latin Christianity, Renaissance humanistic textual recovery, neoclassical “Aristotelianism,” early modern Aristotelianism and anti-Aristotelianism, and the nineteenthcentury rehabilitation of Aristotle. This article will summarize briefly pre eighteenth-century interpretations of Aristotle as prolegomena to a close analysis of the works of two eighteenth-century Scotsmen, James Moor [End Page 376] and John Gillies, whose reconfiguration of Aristotle’s Rhetoric, Poetics, and Organon as tools for practical wisdom in modern society anticipated (and, albeit indirectly, influenced) Farrell.2AntiquityTwo distinct strands of Aristotelian reception, the rhetorical-humanistic and technical-philosophical, originated in antiquity. Of these, the rhetorical-humanistic strand was substantially less important. Neither the Poetics nor the Rhetoric was well known in antiquity. The Rhetoric was not the subject of a Greek commentary until the Byzantine period and, although occasionally cited by Greco-Roman rhetoricians including Cicero, Quintilian, and Dionysus of Halicarnassus, was not widely or carefully read.3 The Poetics was also virtually unknown and was never the subject of an ancient commentary.4The Greek commentaries on Aristotle, which are predominantly technical-philosophical in character, include some fifteen thousand pages of extant text. Despite the existence of a distinct ancient Peripatetic school, the majority of commentaries were produced in the Platonic schools, where the works of Aristotle... (shrink)

The aim of this paper is to assess the central role the imagination acquires in Pierre Gassendi’s logic. I trace the structuring scheme of the three acts of the mind—common to a good number of late scholastic and early modern logics—to the Thomistic notion of the movement of reasoning in knowledge and argue that Gassendi revisits this notion in his logic. The three acts scheme is from the beginning a bridge between logic and the natural philosophical treatment of the soul. (...) I show how Gassendi’s take on the three acts is similarly poised between his Logic and his Physics and I discuss the rationale, sources and consequences of his attribution of the three acts to the imagination. I argue for the following points: Gassendi’s conception of the logical role of the imagination answers to his empiricist epistemology, his naturalized view of the mind and his notion of a natural logic; it is also operative in his pairing of the formal mechanism of logical operations with a progressive mechanism of the operations of the mind; and it serves as a counterpart to his experimental understanding of the progress of knowledge.1. (shrink)

This article presents Tarski's Address at the Princeton Bicentennial Conference on Problems of Mathematics, together with a separate summary. Two accounts of the discussion which followed are also included. The central topic of the Address and of the discussion is decision problems. The introductory note gives information about the Conference, about the background of the subjects discussed in the Address, and about subsequent developments to these subjects.

We seek means of distinguishing logical knowledge from other kinds of knowledge, especially mathematics. The attempt is restricted to classical two-valued logic and assumes that the basic notion in logic is the proposition. First, we explain the distinction between the parts and the moments of a whole, and theories of ?sortal terms?, two theories that will feature prominently. Second, we propose that logic comprises four ?momental sectors?: the propositional and the functional calculi, the calculus of asserted propositions, and rules for (...) (in)valid deduction, inference or substitution. Third, we elaborate on two neglected features of logic: the various modes of negating some part(s) of a proposition R, not only its ?external? negation not-R; and the assertion of R in the pair of propositions ?it is (un)true that R? belonging to the neglected logic of asserted propositions, which is usually left unstated. We also address the overlooked task of testing the asserted truth-value of R. Fourth, we locate logic among other foundational studies: set theory and other theories of collections, metamathematics, axiomatisation, definitions, model theory, and abstract and operator algebras. Fifth, we test this characterisation in two important contexts: the formulation of some logical paradoxes, especially the propositional ones; and indirect proof-methods, especially that by contradiction. The outcomes differ for asserted propositions from those for unasserted ones. Finally, we reflect upon self-referring self-reference, and on the relationships between logical and mathematical knowledge. A subject index is appended. (shrink)

Three distinctly different interpretations of Aristotle’s notion of a sullogismos in Prior Analytics can be traced: (1) a valid or invalid premise-conclusion argument (2) a single, logically true conditional proposition and (3) a cogent argumentation or deduction. Remarkably the three interpretations hold similar notions about the logical relationships among the sullogismoi. This is most apparent in their conflating three processes that Aristotle especially distinguishes: completion (A4-6)reduction(A7) and analysis (A45). Interpretive problems result from not sufficiently recognizing Aristotle’s remarkable degree of metalogical (...) sophistication to distinguish logical syntax from semantics and, thus, also from not grasping him to refine the deduction system of his underlying logic. While it is obvious that Aristotle most often uses ‘sullogimos’ to denote a valid argument of a certain kind, we show that at Prior Analytics A4-6, 7, 45 Aristotle specifically treats a sullogismos as an elemental argument pattern having only valid instances and that such a pattern then serves as a rule of deduction in his syllogistic logic. By extracting Aristotle’s understanding of three proof-theoretic processes, this paper provides new insight into what Aristotle thinks reasoning syllogistically is and, moreover, it resolves three problems in the most recent interpretation that takes a sullogismos to be a deduction. (shrink)

An investigation of Proclus' logic of the syllogistic and of negations in the Elements of Theology, On the Parmenides, and Platonic Theology. It is shown that Proclus employs interpretations over a linear semantic structure with operators for scalar negations (hypemegationlalpha-intensivum and privative negation). A natural deduction system for scalar negations and the classical syllogistic (as reconstructed by Corcoran and Smiley) is shown to be sound and complete for the non-Boolean linear structures. It is explained how Proclus' syllogistic presupposes converting the (...) tree of genera and species from Plato's diairesis into the Neoplatonic linear hierarchy of Being by use of scalar hyper and privative negations. (shrink)

In 1952, Quine showed that the problem of reducing a propositional formula to a simplest normal equivalent can be solved in two steps, viz., (i) express the given formula, Φ, equivalently as the disjunction of all its prime implicants, and (ii) find all non-redundant disjunctions of the latter that are equivalent to Φ (Quine 1952). However, it seems not generally known that an ingenious form of the same two-step process was published by Hugh McColl in 1878.

De acuerdo con los principales enfoques al respecto la lógica de los estoicos es principalmente un sistema deductivo, lo que, en términos actuales, ha sido visto como un sistema de lógica proposicional. La obra de Crísipo acerca de los cinco argumentos indemostrables constituye la principal base de dicho sistema. En este artículo se examina la naturaleza de dichos cinco indemostrables así como el llamando teorema de Antipatro y los esquemas básicos de inferencia, o zemas. Por otra parte y en particular, (...) sostengo que dichos argumentos indemostrables tienen otro importante rol para la filosofía y la historia de la lógica, cual es el de constituirse en una justificación de la deducción, un problema central en el presente. Se analiza, primero, la justificación por los indemostrables y por el principio de condicionalización y, segundo, la justificación cognitiva de la lógica implícita en un sistema estoico. (shrink)

Older approaches to planning lack the capacity to be responsive to complexity. A new philosophy supporting a new mode of practice could improve significantly the capacity of society to cope with complexity in design, planning, and policy making. The new philosophy and practice must be generic; in other words, it must be divorced in its philosophy and approach from any particular kind of planning activity. It must emphasize the capacity to enhance the work of groups in designing new conceptual structures (...) whether they be plans, policies, or tangible products. (shrink)

The aspects of Erhard Weigel's Analysis Aristotelica ex Euclide restituta that foreshadowed and helped form some characteristics of symbolic logic are highlighted: first, the idea of a pure form of a logical syllogism or of a mathematical proof and, second, a tentative arithmetisation of some aspects of logic. Also, Weigel's emphasis on the role of symbols and figures in the process of mathematical proof is discussed.

Recent debates concerning the nature of epistemic justification primarily turn on two distinctions: the objective-subjective distinction and the internal-external distinction. John Pollock has defended a view that is both internalist and subjectivist. He has provided a novel, naturalized account of epistemic justification. In this paper, I argue that data from cognitive psychology and biology is radically at odds with Pollock's project.

This book proposes to identify three long-term structures in causal reasoning - in particular, in terms of the relationship between cause and identity - that appear to be of value in categorizing and organizing various trends in philosophical thought.<br>Such conceptual schemes involve a host of philosophical dilemmas (such as the problem of relativism), which are examined in the first chapter. A number of naturalistic and transcendental approaches to this problem are also analysed.<br>In particular, the book attempts to construct a theoretical (...) basis for Foucault's tripartite classification of epistemological structures in European thought.<br>The final chapter attempts to buttress the above schema by extending the analysis from cause and identity to growth, change, and stability, critiquing certain ideas of Foucault and Heidegger, as well as examining the contemporary thought of process philosophy and complexity theory.<br><br>Contents<br><br>Contents: Plurality and Causality - What is a Paradigm? - Paradigms and Causal Structure - Universality and Mathesis Universalis - Temporality and Visibility - Classical and Modern Probability Theory - The Environment and Non-Monotonicity - The Marburg School and the Limit Concept; Foucault's concept of 'Man' - Nineteenth Century Philosophy of Science - A Dynamic Model - Foucault and the Birth of the Clinic - Process, Growth and Complexity - Time and History. (shrink)