In this paper, I identify the source of the differences between classical logic and many-valued logics (including fuzzy logics) with respect to the set of valid formulas and the set of inferences sanctioned. In the course of doing so, we find the conditions that are individually necessary and jointly sufficient for any many-valued semantics (again including fuzzy logics) to validate exactly the classically valid formulas, while sanctioning exactly the same set of inferences as classical logic. This in turn shows, contrary (...) to what has sometimes been claimed, that at least one class of infinite-valued semantics is axiomatizable. (shrink)

Euclid’s Elements inspired a number of foundationalist accounts of mathematics, which dominated the epistemology of the discipline for many centuries in the West. Yet surprisingly little has been written by recent philosophers about this conception of mathematical knowledge. The great exception is Imre Lakatos, whose characterisation of the Euclidean Programme in the philosophy of mathematics counts as one of his central contributions. In this essay, we examine Lakatos’s account of the Euclidean Programme with a critical eye, and suggest an alternative (...) picture which builds on his work, but differs in a number of important respects. (shrink)

This entry introduces the reader to the main ideas in Frege's philosophy of logic, mathematics, and language.

Da bi ocenil Fregejev prispevek k utemeljitvi moderne logike se je avtor v svojem prispevku vrnil v preteklost, do Leibnizove lingua characteristica. Vzporednic ni težko najti: odprava dvoumja v govorici in zgradba enoznačnega jezika na tej osnovi, možnost razrešitve spoznavne moči s kalkulom, kar ločuje leibnizoviko tradicijo od kartezijanske. Srž obeh teorij je en in isti boj znanstvenega govora z govorico, razlika pa je v načinu, kako prehod k zapisu udejani ideal calculus ratiocinator. Različni načini, kako so elementi tega boja (...) med seboj povezani, lahko nudijo tudi osnove za premero specifike družbene razsežnosti obeh pristopov. (shrink)

Many historians of analytic philosophy consider the early philosophy of Moore, Russell and Wittgenstein as much more neo-Hegelian as once believed. At the same time, the authors who closely investigate Green, Bradley and Bosanquet find out that these have little in common with Hegel. The thesis advanced in this chapter is that what the British (ill-named) neo-Hegelians brought to the early analytic philosophers were, above all, some ideas of Lotze, not of Hegel. This is true regarding: (i) Lotze’s logical approach (...) to practically all philosophical problems; (ii) his treating of the concepts relation, structure (constructions) and order; (iii) the discussion of the concepts of states of affairs, multiple theory of judgment, general logical form; (iv) some common themes like panpsychism and contemplating the world sub specie aeternitatis. (shrink)

A general survey of Frege's views on truth, the paper explores the problems in response to which Frege's distinctive view that sentences refer to truth-values develops. It also discusses his view that truth-values are objects and the so-called regress argument for the indefinability of truth. Finally, we consider, very briefly, the question whether Frege was a deflationist.

تقریباً قاطبة فلاسفة اسلامی به صورت مستقیم یا غیرمستقیم به مسئلة «تشخّص» پرداخته و پاسخ‌هایی را ارائه داشته‌اند و ازین رو، سرگذشت این بحث به طور کلّی در سنّت فلسفی اسلام قابل مطالعة جدّی و تدقیقات همه‌جانبه است، امّا در اینجا قصد ما پرداختن به جنبه‌ای از نقش فارابی در تطوّر و تکامل این سیر تاریخی است، تا از این طریق پرتوهایی بر زوایای مغفول و ناشناخته‌تر سنّت عقلانی مسلمانان افکنده شود. یکی از کسانی که این بحث را بسی بیش (...) از پیش محلّ توجّه متفکّران قرار داد، ملّاصدراست که به تبع فلسفة اصالت وجود خویش، مطالب بدیعی را در باب تشخّص ابراز نمود. یکی از نکات اصلی ملّاصدرا این است که مساوقت «تشخّص» و «وجود» را به فارابی نسبت می‌دهد. در نزد اندیشمندان دورة قدیم یا حتّی دوره معاصر، هیچ‌گاه تردیدی یا مطالعه‌ای در باب صحّت این انتساب صورت نگرفته است. این مقاله بر آن است تا انتساب تقریباً به رسمیّت شناخته شده به فارابی را که از سوی ملّاصدرا صورت گرفته است مطمح‌نظر قرار داده و از رهگذر برخی مستندات متنی و تاریخی نشان دهد که این انتساب می‌تواند تا حدّ زیادی محلّ مناقشه باشد، و حتّی اساساً این مطلب که فارابی بحثی ذیل عنوان «تشخّص» داشته است خود بسیار متزلزل به نظر می‌رسد. (shrink)

Conventional approaches to consciousness assume that our current science tells us within tolerable limits what physical nature is. Because nature so understood cannot explain consciousness as we seem to experience it ourselves, explaining consciousness becomes a problem. One solution is to rethink what consciousness is so that it becomes the sort of thing our current natural science could in principle explain. Whitehead takes the opposite approach, using the existence of consciousness as a clue to what nature must be if it (...) can generate something like consciousness. The justification for this approach can be found in Whitehead’s implicit indictment of descriptive phenomenology. According to Whitehead, the seemingly insoluble problem of explaining consciousness naturalistically is an artifact created by the assumption that consciousness faithfully samples the world, when in fact it obscures the very aspects of nature that are indispensable to understanding how anything, including consciousness itself, could emerge through a physical process. (shrink)

Today it would be considered "bad Platonic metaphysics" to think that among all the concrete instances of a property there could be a universal instance so that all instances had the property by virtue of participating in that concrete universal. Yet there is a mathematical theory, category theory, dating from the mid-20th century that shows how to precisely model concrete universals within the "Platonic Heaven" of mathematics. This paper, written for the philosophical logician, develops this category-theoretic treatment of concrete universals (...) along with a new concept to abstractly model the functions of a brain. (shrink)

In epoca medievale si è molto discusso su alcuni concetti chiave come prova o giustificazione. La teoria della prova contenuta nei trattati di logica medievale prende il nome tecnico di consequentia, che è un tipo di ragionamento fondato sul passaggio dalla concessione (o negazione) di uno o più enunciati denominati antecedenti alla concessione (o negazione) di uno o più enunciati denominati conseguenti. Questo tipo di teoria ha avuto un correlato a livello dei singoli termini che compongono l’enunciato all'interno della teoria (...) nota come suppositio terminorum. Prende, infatti, il nome di descensus, la regola che permette la verifica del passaggio da un termine maggiore (un termine comune) ad un termine minore (che denota individui). La stessa definizione di alcune ramificazioni della teoria della suppositio è col-legata alla possibilità di ammettere o meno il descensus cioè questa "discesa" da un termine comune ad una congiunzione o disgiunzione di termini singolari. Il presente lavoro intende descrivere la teoria del descensus come un tipo particolare di consequentia mostrandone le connessioni con le moderne tecniche logiche. I trattati che si affronteranno appartengono al XIV e al XV secolo, cioè ad un periodo caratterizzato da una sistemazione della materia che li rende confrontabili con un quadro teorico unitario. (shrink)

No tratado intitulado Segundos Analíticos, Aristóteles desenvolve uma teoria da demonstração científica e da ciência demonstrativa. Ali, o conhecimento científico é descrito pelo filósofo como envolvendo uma certa "necessidade". Alguns intérpretes associam esta noção de necessidade à necessidade modal, pertinente à silogística modal de Aristóteles. Esta interpretação, todavia, tornaria o modelo de ciência proposto nos Analíticos incompatível com os explananda das ciências da natureza, cuja cientificidade o próprio Aristóteles reiteradamente defendeu. A fim de evitar este inconveniente, abordamos e reconstruímos a (...) mencionada interpretação, reconhecemos suas falhas e propomos, seguindo outra tendência da literatura secundária, uma leitura alternativa da noção de necessidade como adequação explanatória, a qual garantiria a cientificidade dos fenômenos naturais. (shrink)

Although the theory of the assertoric syllogism was Aristotle's great invention, one which dominated logical theory for the succeeding two millenia, accounts of the syllogism evolved and changed over that time. Indeed, in the twentieth century, doctrines were attributed to Aristotle which lost sight of what Aristotle intended. One of these mistaken doctrines was the very form of the syllogism: that a syllogism consists of three propositions containing three terms arranged in four figures. Yet another was that a syllogism is (...) a conditional proposition deduced from a set of axioms. There is even unclarity about what the basis of syllogistic validity consists in. Returning to Aristotle's text, and reading it in the light of commentary from late antiquity and the middle ages, we find a coherent and precise theory which shows all these claims to be based on a misunderstanding and misreading. (shrink)

Is it possible for an argument to have either zero premises or an infinite number of premises? I shall argue that regardless of how you conceive of arguments you should accept that an argument could have an infinite number of premises. The zero case is more complicated since the matter seems to depend not only on the metaphysics of arguments, but also the nature and function of arguing. I shall argue that at least a plausible case can be made for (...) the possibility of zero premise arguments. (shrink)

Conditional logics were originally developed for the purpose of modeling intuitively correct modes of reasoning involving conditional—especially counterfactual—expressions in natural language. While the debate over the logic of conditionals is as old as propositional logic, it was the development of worlds semantics for modal logic in the past century that catalyzed the rapid maturation of the field. Moreover, like modal logic, conditional logic has subsequently found a wide array of uses, from the traditional (e.g. counterfactuals) to the exotic (e.g. conditional (...) obligation). Despite the close connections between conditional and modal logic, both the technical development and philosophical exploitation of the latter has outstripped that of the former, with the result that noticeable lacunae exist in the literature on conditional logic. My dissertation addresses a number of these underdeveloped frontiers, producing new technical insights and philosophical applications. -/- I contribute to the solution of a problem posed by Priest of finding sound and complete labeled tableaux for systems of conditional logic from Lewis' V-family. To develop these tableaux, I draw on previous work on labeled tableaux for modal and conditional logic; errors and shortcomings in recent work on this problem are identified and corrected. While modal logic has by now been thoroughly studied in non-classical contexts, e.g. intuitionistic and relevant logic, the literature on conditional logic is still overwhelmingly classical. Another contribution of my dissertation is a thorough analysis of intuitionistic conditional logic, in which I utilize both algebraic and worlds semantics, and investigate how several novel embedding results might shed light on the philosophical interpretation of both intuitionistic logic and conditional logic extensions thereof. -/- My dissertation examines deontic and connexive conditional logic as well as the underappreciated history of connexive notions in the analysis of conditional obligation. The possibility of interpreting deontic modal logics in such systems (via embedding results) serves as an important theoretical guide. A philosophically motivated proscription on impossible obligations is shown to correspond to, and justify, certain (weak) connexive theses. Finally, I contribute to the intensifying debate over counterpossibles, counterfactuals with impossible antecedents, and take—in contrast to Lewis and Williamson—a non-vacuous line. Thus, in my view, a counterpossible like "If there had been a counterexample to the law of the excluded middle, Brouwer would not have been vindicated" is false, not (vacuously) true, although it has an impossible antecedent. I exploit impossible (non-normal) worlds—originally developed to model non-normal modal logics—to provide non-vacuous semantics for counterpossibles. I buttress the case for non-vacuous semantics by making recourse to both novel technical results and theoretical considerations. (shrink)

The dissertation is an investigation into the structure of Aristotle's modal propositions through careful attention to the text of the Prior Analytics. I take account not only of recent attempts to formalize Aristotle's modal syllogistic but also of the discussion that Aristotle himself provides about modal statements. I provide evidence that his modal propositions are to be construed in a de re manner and then go on to investigate the problems raised by a de re analysis, particularly those problems concerned (...) with Aristotle's modal conversion principles. A large part of my project is to show that these can be given a valid de re analysis that sits well with the results Aristotle sketches. Terms in modal syllogistic premises are shown to be restricted in ways that reflect Aristotle's early metaphysics and notions of predication. (shrink)

The main thrust of the argument of this thesis is to show the possibility of articulating a method of construction or of synthesis--as against the most common method of analysis or division--which has always been (so we shall argue) a necessary component of scientific theorization. This method will be shown to be based on a fundamental synthetic logical relation of thought, that we shall call inversion--to be understood as a species of logical opposition, and as one of the basic monadic (...) logical operators. Thus the major objective of this thesis is to This thesis can be viewed as a response to Larry Laudan's challenge, which is based on the claim that ``the case has yet to be made that the rules governing the techniques whereby theories are invented (if any such rules there be) are the sorts of things that philosophers should claim any interest in or competence at.'' The challenge itself would be to show that the logic of discovery (if at all formulatable) performs the epistemological role of the justification of scientific theories. We propose to meet this challenge head on: a) by suggesting precisely how such a logic would be formulated; b) by demonstrating its epistemological relevance (in the context of justification) and c) by showing that a) and b) can be carried out without sacrificing the fallibilist view of scientific knowledge. OBJECTIVES: We have set three successive objectives: one general, one specific, and one sub-specific, each one related to the other in that very order. (A) The general objective is to indicate the clear possibility of renovating the traditional analytico-synthetic epistemology. By realizing this objective, we attempt to widen the scope of scientific reason or rationality, which for some time now has perniciously been dominated by pure analytic reason alone. In order to achieve this end we need to show specifically that there exists the possibility of articulating a synthetic (constructive) logic/reason, which has been considered by most mainstream thinkers either as not articulatable, or simply non-existent. (B) The second (specific) task is to respond to the challenge of Larry Laudan by demonstrating the possibility of an epistemologically significant generativism. In this context we will argue that this generativism, which is our suggested alternative, and the simplified structuralist and semantic view of scientific theories, mutually reinforce each other to form a single coherent foundation for the renovated analytico-synthetic methodological framework. (C) The third (sub-specific) objective, accordingly, is to show the possibility of articulating a synthetic logic that could guide us in understanding the process of theorization. This is realized by proposing the foundations for developing a logic of inversion, which represents the pattern of synthetic reason in the process of constructing scientific definitions. (shrink)

Toisaalta ennennäkemätön äärettömien joukko-opillisten menetelmien hyödyntäminen sekä toisaalta epäilyt niiden hyväksyttävyydestä ja halu oikeuttaa niiden käyttö ovat ratkaisevasti muovanneet vuosisatamme matematiikkaa ja logiikkaa. Tämän kehityksen vaikutus nykyajan filosofiaan on myös ollut valtaisa; merkittävää osaa siitä ei voi edes ymmärtää tuntematta sen yhteyttä tähän matematiikan ja logiikan vallankumoukseen. Lähestymistapoja, jotka tavalla tai toisella hyväksyvät äärettömän matematiikan ja perinteisten logiikan sääntöjen (erityisesti kolmannen poissuljetun lain) soveltamisen myös sen piirissä, on tullut tavaksi kutsua klassiseksi matematiikaksi ja logiikaksi erotuksena nämä hylkäävistä radikaaleista intuitionistisista ja (...) konstruktivistisista opeista. (shrink)

Aristotle's General Definition of the Syllogism may be taken as consisting of two parts: the Inferential Conditions and the Final Clause. Although this distinction is well known, traditional interpretations neglect the Final Clause and its influence on syllogistic. Instead, the aforementioned tradition focuses on the Inferential Conditions only. We intend to show that this neglect has severe consequences not just on syllogistic but on the whole exegesis of Aristotle's Prior Analytics I. Due to these consequences, our objective is to analyse (...) the General Definition's Final Clause and its consequences on syllogistic. We propose a reading of the Final Clause as an additional criterion for distinguishing some arguments as properly syllogistic ones and as a main theme which connects all parts of the Prior Analytics I into one coherent piece of work. (shrink)

Is it possible to distinguish communities of arguers by tracking the argumentation schemes they employ? There are many ways of relating schemes to communities, but not all are productive. Attention must be paid not only to the admissibility of schemes within a community of argumentational practice, but also to their comparative frequency. Two examples are discussed: informal mathematics, a convenient source of well-documented argumentational practice, and anthropological evidence of nonstandard reasoning.

In this paper we discuss the difference between (...) proliferations of logic systems, the questions of relativity and universality of logic and the position and interaction of logic with regards to other sciences such as physics, biology, mathematics and computer science. (shrink)

This thesis is on the history and philosophy of logic and semantics. Logic can be described as the ‘science of reasoning’, as it deals primarily with correct patterns of reasoning. However, logic as a discipline has undergone dramatic changes in the last two centuries: while for ancient and medieval philosophers it belonged essentially to the realm of language studies, it has currently become a sub-branch of mathematics. This thesis attempts to establish a dialogue between the modern and the medieval traditions (...) in logic, by means of ‘translations’ of the medieval logical theories into the modern framework of symbolic logic, i.e. formalizations. One of its conclusions is that, when properly understood within their own framework, the interest of medieval logical theories for modern investigations go beyond mere historical interest, but that a thorough conceptual analysis of such theories must be undertaken in order to avoid conceptual misprojections. While such translations of medieval into modern logic have been attempted before, the approach presented here is innovative in that attention is paid to the similarities as well as to the dissimilarities between the two traditions, and to what can be learned from the medieval masters for modern investigations in logic and semantics. (shrink)

Although most scholars trace the Liar Paradox to Plato’s contemporary, Eubulides, the paper argues that Plato builds something very like the Liar Paradox into the very structure of his dialogues with significant consequences for understanding his views. After a preliminary exposition of the liar paradox it is argued that Plato builds this paradox into the formulation of many of his central doctrines, including the “Divided Line” and the “Allegory of the Cave” and the “Ladder of Love”. Thus, Plato may have (...) been the first to formulate the view that Graham Priest calls dialetheism, roughly, the view that some contradictions are, in an illuminating way, inescapable and true. The paper argues that Plato builds this Liar paradox into the formulation of his signature views because he holds that the attempt by finite human beings to theorize about transcendent realities results in the simultaneous necessity, and impossibility, of transgressing the limits of language—leading to the paradoxes. Finally, it is argued that the existence of these paradoxes in these Platonic doctrines is the direct result of an intrinsic hermeneutical circle in Plato’s aforementioned signature views. (shrink)

The paper emphasizes significant resemblances between the Informal Logic Initiative and the Lvov-Warsaw School – the Polish philosophical movement, the rise of which is associated with “the Golden Age of Science and Letters”. The correspondence between informal logic and the logical studies of the LWS will be explored by discussing their subject-matter, goals, and methods. The project focused on applying logical studies of the LWS in analyzing and assessing arguments will be proposed.

Aristotle studies syllogistic argumentation in Sophistical Refutations and Prior Analytics. In the latter he focuses on the formal and syntactic character of arguments and treats the sullogismoi and non-sullogismoi as argument patterns with valid or invalid instances. In the former Aristotle focuses on semantics and rhetoric to study apparent sullogismoi as object language arguments. Interpreters usually take Sophistical Refutations as considerably less mature than Prior Analytics. Our interpretation holds that the two works are more of a piece than previously believed (...) and, indeed, that Aristotle's treatment of fallacious reasoning presupposes the results of the formal theory. (shrink)

In the analysis of syllogistic reasoning, a type of inference patternbased on the chaining of terms through quantified statements, two interpretationsabout them can be found in the literature. One is the so-called set-based interpretation,which assumes that quantified statements and syllogisms talk aboutquantity-relationships between sets. The other one, the so-called conditionalinterpretation, assumes that they talk about conditional propositions and howstrong are the links between the antecedent and the consequent. In this paper,we expose both models and formulate three relevant questions to be (...) taken intoaccount for a further development of this type of reasoning. (shrink)

A commonplace of modern logic is that traditional logic, because it accepted the supposedly mistaken inference from general to particular propositions, perceived as valid a good number of invalid inference patterns. Yet many people find the allegedly invalid inference patterns intuitively valid. Four arguments that might be used to justify modern logic's judgment fail to provide good reason to provide modern logic pride of place. Of the three responses to failure of the arguments for preferring mode rn to traditional logic (...) considered, the most radical is recommended. (shrink)

This paper discusses the reports in Diogenes Laertius and in Sextus Empiricus concerning the classification of propositions. It is argued that the material in Sextus uses a source going back to the Dialectical school whose most prominent members were Diodorus Cronus and Philo of Megara. The material preserved in Diogenes Laertius, on the other hand, goes back to Chrysippus.

The nominalist attitude in medieval logic supported a fully extensional conception of the sense of expressions. Many arguments against this approach were raised at that time. I would like to show in this article that there is a extensional conception of notions in current logic, namely in the interpretation of formal theories and the creation models of them and that, and how, traditional arguments against the extensional conception are relevant also for logic today.

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)