This book is about one of the most baffling of all paradoxes – the famous Liar paradox. Suppose we say: 'We are lying now'. Then if we are lying, we are telling the truth; and if we are telling the truth we are lying. This paradox is more than an intriguing puzzle, since it involves the concept of truth. Thus any coherent theory of truth must deal with the Liar. Keith Simmons discusses the solutions proposed by medieval philosophers (...) and offers his own solutions and in the process assesses other attempts to solve the paradox. Unlike such attempts, Simmons' 'singularity' solution does not abandon classical semantics and does not appeal to the kind of hierarchical view found in Barwise's and Etchemendy's The Liar. Moreover, Simmons' solution resolves the vexing problem of semantic universality – the problem of whether there are semantic concepts beyond the expressive reach of a natural language such as English. (shrink)

In “Professional Detachment: The Executioner of Paris,” I concluded with the cheap and some would say libelous suggestion that lawyers might accurately be described as serial liars, because they repeatedly try to induce others to believe in the truth of propositions or in the validity of arguments that they believe to be false. Good lawyers have responded with some indignation that, in calling zealous advocacy “lying,” I have misdescribed the practice of law. I wish to explain why I believe that (...) it is the practice of lawyering that engages in misdescription. (shrink)

The purpose of this note is to present a strong form of the liar paradox. It is strong because the logical resources needed to generate the paradox are weak, in each of two senses. First, few expressive resources required: conjunction, negation, and identity. In particular, this form of the liar does not need to make any use of the conditional. Second, few inferential resources are required. These are: (i) conjunction introduction; (ii) substitution of identicals; and (iii) the inference: (...) From ¬(p ∧ p), infer ¬ p. It is, interestingly enough, also essential to the argument that the ‘strong’ form of the diagonal lemma be used: the one that delivers a term λ such that we can prove: λ = ¬ T(⌈λ⌉); rather than just a sentence Λ for which we can prove: Λ ≡ ¬T(⌈Λ⌉). The truth-theoretic principles used to generate the paradox are these: ¬(S ∧ T(⌈¬S⌉); and ¬(¬S ∧ ¬T(⌈¬S⌉). These are classically equivalent to the two directions of the T-scheme, but they are intuitively weaker. The lesson I would like to draw is: There can be no consistent solution to the Liar paradox that does not involve abandoning truth-theoretic principles that should be every bit as dear to our hearts as the T-scheme. So we shall have to learn to live with the Liar, one way or another. (shrink)

The Liar Paradox is an argument that arrives at a contradiction by reasoning about a Liar Sentence. The classical Liar Sentence is the self-referential sentence “This sentence is false.”.

Contextualist approaches to the Liar Paradox postulate the occurrence of a context shift in the course of the Liar reasoning. In particular, according to the contextualist proposal advanced by Charles Parsons and Michael Glanzberg, the Liar sentence L doesn’t express a true proposition in the initial context of reasoning c, but expresses a true one in a new, richer context c', where more propositions are available for expression. On the further assumption that Liar sentences involve propositional (...) quantifiers whose domains may vary with context, the Liar reasoning is blocked. But why should context shift? We argue that the paradox involves principles of contextualist reflection that explain, by analogy with well-known reflection principles for arithmetic, why context must shift from c to c' in the course of the Liar reasoning. This provides a diagnosis of the Liar Paradox—one that equally applies to two revenge arguments against contextualist approaches, one recently advanced by Andrew Bacon, the other mentioned by Charles Parsons and more recently revived by Cory Juhl. (shrink)

Semantic and soritical paradoxes challenge entrenched, fundamental principles about language - principles about truth, denotation, quantification, and, among others, 'tolerance'. Study of the paradoxes helps us determine which logical principles are correct. So it is that they serve not only as a topic of philosophical inquiry but also as a constraint on such inquiry: they often dictate the semantic and logical limits of discourse in general. Sixteen specially written essays by leading figures in the field offer new thoughts and arguments (...) about the paradoxes. (shrink)

The Liar paradox arises when we consider a sentence that says of itself that it is not true. If such self-referential sentences exist? and examples like?This sentence is not true? certainly suggest this?, then our logic and standard notion of truth allow to infer a contradiction: The Liar sentence is true and not true. What has gone wrong? Must we revise our notion of truth and our logic? Or can we dispel the common conviction that there are such (...) self-referential sentences? The present study explores the second path.0After comparing the Liar reasoning in formal and informal logic and showing that there are no Gödelian Liar sentences, the study moves on from the semantics of self-reference to the metaphysics of expressions and proposes a novel solution to the Liar paradox: Meaningful expressions are distinct from their syntactic bases and exist only relative to contexts. Detailed semantico-metaphysical arguments show that in this dynamic setting, an object can be referred to only after it has started to exist. Hence the circular reference needed in the Liar paradox cannot occur, after all. As this solution is contextualist, it evades the expressibility problems of other proposals. (shrink)

This article is about self-referential arguments that are akin to the paradox of the liar. They make reference to their own validity, invalidity, soundness, unsoundness, or to the truth or falsity of their own premises or conclusions. Several very puzzling examples of such arguments are considered and their paradoxicality is defended against objections.

The liar paradox in its simplest form is the following argument. Consider the sentence 'this sentence is false'; call that the "liar sentence". Suppose the liar sentence is true. Then, since it says it is false, the liar sentence is false. So our supposition that it is true was mistaken, and the liar sentence must be false. But that's precisely what the liar sentence says, so it is true after all. The liar (...) sentence is, therefore, both true and false---an absurd result. ;Hans Herzberger has argued that several solutions to the Grelling paradox exhibit a common pattern: the very devices we introduce in order to avoid one version of the paradox are integral components of new versions of the paradox. Herzberger suggests that this is typical of semantic paradox in general. Chapters 1, 2, and 3 of this dissertation examine several possible solutions to the liar---especially appeals to language levels and to contexts---and attempt to locate these possible solutions in Herzberger's pattern. ;There is some reason to think that this pattern is inescapable---that is, that the liar paradox is ultimately unsolvable---so the remaining two chapters of this dissertation explore what follows from the claim that it is unsolvable. Chapter 4 develops an argument from the claim that the liar is unsolvable to the claim that we cannot understand ourselves. Chapter 5, then, attempts to make sense of this circumstance by invoking a Nietzschean view of thinking and truth---perspectivalism, which holds that all thinking concerns interpretation and that there are no uninterpreted facts. Given some perspectivalist assumptions, we can see how it is inevitable that we will be unable to understand ourselves---and how we can nevetherless attain a certain limited kind of understanding. Perspectivalism also recommends a certain intellectual humility: if everything is interpretation, then no view of mine can be a comprehensive and accurate view of the way the world really is. This by itself is not a surprising claim; the surprising claim is that the liar paradox is the basis of it. (shrink)

The purpose of this paper is to philosophically examine how disinformation from state officials and politicians affects the right to access to information and political participation. Next to the more straightforward implications for political self-determination, the paper examines how active dissemination of lies by figures of epistemic authority can be framed as a human rights issue and affects trust patterns between citizens, increases polarization, impedes dialogue, and obstructs access to politically relevant information by gatekeeping knowledge. Analyzing European Convention on Human (...) Rights (ECHR) case law, the paper argues that human rights law provides some argumentative basis for extending individuals’ rights as epistemic and political agents towards a “right to truth spoken by politicians”. However, challenges in balancing a possible restriction of lies and assessing the real effective harm that comes from them remain, potentially leading to a vacuum of rights protection for less visible long-term harm to individuals and public discourse. In order to have a real chance at tackling the harmful consequences of publicly told lies from a human rights perspective, it is necessary to rethink the notion of harm to encompass more complex and abstract forms of politico-epistemic damage to individuals and the public. (shrink)

Al-Taftāzānī introduces the Liar Paradox, in a commentary on al-Rāzī, in a short passage that is part of a polemic against the ethical rationalism of the Muʿtazila. In this essay, we consider his remarks and their place in the history of the Liar Paradox in Arabic Logic. In the passage, al-Taftāzānī introduces Liar Cycles into the tradition, gives the paradox a puzzling name—the fallacy of the “irrational root” —which became standard, and suggests a connection between the paradox (...) and what it tells us about truth and falsehood, and arguments for divine voluntarism and what they tell us about the nature of goodness and badness. On this last point, we also discuss a passage from al-Rāzī, which suggests similar connections. (shrink)

The liar paradox is still an open philosophical problem. Most contemporary answers to the paradox target the logical principles underlying the reasoning from the liar sentence to the paradoxical conclusion that the liar sentence is both true and false. In contrast to these answers, Buddhist epistemology offers resources to devise a distinctively epistemological approach to the liar paradox. In this paper, I mobilise these resources and argue that the liar sentence is what Buddhist epistemologists call (...) a contradiction with one’s own words. I situate my argument in the works of Dignāga and Dharmakīrti and show how Buddhist epistemology answers the paradox. (shrink)

Semantic and soritical paradoxes challenge entrenched, fundamental principles about language - principles about truth, denotation, quantification, and, among others, 'tolerance'. Study of the paradoxes helps us determine which logical principles are correct. So it is that they serve not only as a topic of philosophical inquiry but also as a constraint on such inquiry: they often dictate the semantic and logical limits of discourse in general. Sixteen specially written essays by leading figures in the field offer new thoughts and arguments (...) about the paradoxes. (shrink)

There is no need to prove the significance to philosophy of the famous liar paradox. Attempts to solve it have not ceased over the course of many centuries, from hoary antiquity to our own day. The failure of attempts undertaken within the bounds of everyday, natural languages has led many philosophers, particularly of the positivist trend, to pessimistic conclusions with respect to the potentials of such languages. This is very clearly evident, for example, in the statement of A. Tarski, (...) who writes: "The liar paradox made its first appearance in our discussions as a kind of evil force possessed of great destructive energy. It compels us to reject all attempts to explicate the notion of truth for natural languages and to confine ourselves to the formalized languages of scientific reasoning." Tarski's viewpoint has been repeatedly criticized. We should prefer not to cast doubt on the significance of that highly valuable criticism. However, we cannot fail to observe that Tarski's notion retains its force so long as its basic argument - the insolubility of the liar paradox within the confines of natural languages - remains standing. (shrink)

If we want to retain classical logic and standard syntax in light of the liar, we are forced to restrict the T-schema. The traditional philosophical justification for this is sentential – liar sentences somehow malfunction. But the standard formal way of implementing this is conditional, our T-sentences tell us that if “p” does not malfunction, then “p” is true if and only if p. Recently Bacon and others have pointed out that conditional T-restrictions like this flirt with incoherence. (...) If we want to keep the “malfunction” motivation, our only other option is to non-conditionally restrict the T-schema, but Field and others have given powerful philosophical and technical arguments against this kind of approach. Here I argue that if we really take the philosophical motivation for restricting T-sentences seriously, we can explain why conditional restrictions fail, answer Field's argument, and reason in a coherent way about truth using a non-conditional restriction strategy. This cracks the door open for a fully classical response to the liar and related paradoxes. In closing, I argue that, when properly understood, this kind of “restriction” is not really a restriction at all. If this is right, then the holy grail of liar studies (classical logic, naïve truth, and standard syntax) may yet be attainable. (Note for readers: when this paper was first put online, the typesetters had changed some instances of corners to brackets, leading to confusion. The paper has now been corrected online by PPR, so please make sure you have the corrected version before reading or citing.). (shrink)

This article informally presents a solution to the paradoxes of truth and shows how the solution solves classical paradoxes (such as the original Liar) as well as the paradoxes that were invented as counterarguments for various proposed solutions (“the revenge of the Liar”). This solution complements the classical procedure of determining the truth values of sentences by its own failure and, when the procedure fails, through an appropriate semantic shift allows us to express the failure in a classical (...) two-valued language. Formally speaking, the solution is a language with one meaning of symbols and two valuations of the truth values of sentences. The primary valuation is a classical valuation that is partial in the presence of the truth predicate. It enables us to determine the classical truth value of a sentence or leads to the failure of that determination. The language with the primary valuation is precisely the largest intrinsic fixed point of the strong Kleene three-valued semantics (LIFPSK3). The semantic shift that allows us to express the failure of the primary valuation is precisely the classical closure of LIFPSK3: it extends LIFPSK3 to a classical language in parts where LIFPSK3 is undetermined. Thus, this article provides an argumentation, which has not been present in contemporary debates so far, for the choice of LIFPSK3 and its classical closure as the right model for the truth predicate. In the end, an erroneous critique of Kripke-Feferman axiomatic theory of truth, which is present in contemporary literature, is pointed out. (shrink)

There is a prevalent view against the disquotational and the minimal theories of truth, that the most sensible solution to the Liar—that is, the gappy solution—is not available to them. I would like to argue that, though this solution is unavailable to the two theories, the prevailing argument and the reasoning behind this view are wrong. This paper mainly focuses on Simmons’ “Deflationary Truth and the Liar” (1999), within which the idea that disquotationalism can take the (...) class='Hi'>Liar in its stridein terms of the gappy option is thoroughly criticised. Albeit Simmons’ account is about disquotationalism, it is in fact about truth theories with the disquotational feature. For Horwich’s minimal theory of truth to be feasible, it is in need of providing an account of which the primary truth bearers are utterances or sentences. The reasoning behind Simmons’ account and his argument is a widely accepted but in my opinion mistaken reading of deflationary theories, reading the deflationary axiom schemata as emphasising the redundant feature of the true predicate only. By analysing and criticising this reasoning the mistakes of this interpretation of the deflationary theories of truth are revealed. Simmons bases his argument on two premises: taking disquotational theory of truth asdefinitional theory and considering the main feature of the disquotational truth predicate as eliminability. In terms of the notion of parasitic liar, I will argue that Simmons fails to show the plausibility of one crucial premise of his argument—that is, the paradoxical or the pathological feature is missing from the disquotational mirrors of the Liar. I will further show what deflationary feature is misunderstood by those accounts similar to Simmons’. (shrink)

This paper defends an account of compassion and argues for the centrality of compassion to the proper practice of medicine. The argument proceeds by showing that failures of compassion can lead to poor medical treatment and disastrous outcomes. Several case studies are discussed, exemplifying the difference between compassionate and noncompassionate responses to patients seeking help. Arguments are offered in support of approaching reports of persistent pain with a trusting attitude, rather than distrust or skepticism. The article concludes by suggesting (...) educational improvements to encourage compassion. (shrink)

Liar-like paradoxes are typically arguments that, by using very intuitive resources of natural language, end up in contradiction. Consistent solutions to those paradoxes usually have difficulties either because they restrict the expressive power of the language, or else because they fall prey to extended versions of the paradox. Dialetheists, like Graham Priest, propose that we should take the Liar at face value and accept the contradictory conclusion as true. A logical treatment of such contradictions is also put forward, (...) with the Logic of Paradox, which should account for the manifestations of the Liar. In this paper we shall argue that such a formal approach, as advanced by Priest, is unsatisfactory. In order to make contradictions acceptable, Priest has to distinguish between two kinds of contradictions, internal and external, corresponding, respectively, to the conclusions of the simple and of the extended Liar. Given that, we argue that while the natural interpretation of LP was intended to account for true and false sentences, dealing with internal contradictions, it lacks the resources to tame external contradictions. Also, the negation sign of LP is unable to represent internal contradictions adequately, precisely because of its allowance of sentences that may be true and false. As a result, the formal account suffers from severe limitations, which make it unable to represent the contradiction obtained in the conclusion of each of the paradoxes. (shrink)

This chapter contains sections titled: Truth The Liar Tarskian Truth Definition Discussion Conclusion.

This paper develops a classical model for our ordinary use of the truth predicate (1) that is able to address the liar's paradox and (2) that satisfies a very strong version of deflationism. Since the model is a classical in the sense that it has no truth value gaps, the model is able to address Tarski's indictment of our ordinary use of the predicate as inconsistent. Moreover, since it is able to address the liar's paradox, it responds to (...) arguments against deflationism based upon that paradox alone. The model is based upon a notion of the complexity of propositions that a fixed set of speakers might express. A context-sensitive definition of the truth predicate is then provided based upon a class of possible worlds defined in terms of these speakers. Reasonable constraints on the memories and lifetimes of ordinary speakers are used to limit the set of propositions that they might express so that deflationist requirements are satisfied. (shrink)

Most philosophers believe that the Liar Paradox is semantical in character, and arises from difficulties in the predicate “true.” The author argues that the paradox is pragmatic, not semantic, and arises from violations of essential conditions that define statement-making speech acts. The author shows that his solution to the paradox will not only handle the classical Liar sentences that are “necessarily” or “intrinsically” paradoxical, but also sets of Kripke-sentences that are “contingently” paradoxical.

The liar and kindred paradoxes show that we can derive contradictions when we reason in accordance with classical logic from the schema (T) about truth: S is true iff p, where ‘p’ is to be replaced with a sentence and ‘S’ with a name of that sentence. The paper presents two arguments to the effect that the blame lies not with (T) but with classical logic. The arguments derive contradictions using classical logic, but instead of appealing to (T), they (...) invoke semantic claims that seem even harder to reject. The first argument relies on two standard semantic principles that are not disquotational and on the claim that if there is such a thing as the property of being true, then ‘true’ expresses that property. The second argument relies on a schema about meaning: S means that p, where ‘S’ and ‘p’ are to be replaced as before. (shrink)

Semantic and soritical paradoxes challenge entrenched, fundamental principles about language - principles about truth, denotation, quantification, and, among others, 'tolerance'. Study of the paradoxes helps us determine which logical principles are correct. So it is that they serve not only as a topic of philosophical inquiry but also as a constraint on such inquiry: they often dictate the semantic and logical limits of discourse in general. Sixteen specially written essays by leading figures in the field offer new thoughts and arguments (...) about the paradoxes. (shrink)

Argument that Q∃ expresses more than one proposition: (1) Q∃ expresses the proposition that Q∃ expresses some proposition that isn’t true. ((E)) (2) If Q ∃ expresses only true propositions, then the proposition that Q ∃ expresses some proposition that isn’t true is true. ((1)) (3) If Q∃ expresses only true propositions, then some proposition expressed by Q∃ is not true. (2, T) (4) Some proposition expressed by Q ∃ is not true. ((3)) (5) The proposition that Q ∃ (...) expresses some proposition that isn’t true is true. (4, T) (6) Q∃ expresses at least one true proposition. (1,5) (7) Q∃ expresses at least two propositions. (3, 6) (A parallel argument shows that Q∀ expresses both true and false propositions. (shrink)

This paper does not raise objections but spells out problems that I consider at present unsolved within Priest’s view on logic. In light of the state of scientific and other theories and in light of the character of natural languages, Priest’s central arguments do not seem convincing. Next, I offer some six independent obstacles for defining consistency, identifying models and describing the semantics and metatheory of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbf {LP}$$\end{document}.

On the road of inquiry that Parmenides’ goddess recommends, one is to say and conceive that what-is is one, unmoving, continuous, ungenerated, undestroyed, complete, and undivided. Yet the goddess’s arguments in favor of this road use negations, distinctions, divisions, and references to generation and destruction. The requisites of inquiry that she outlines are both defined on and at odds with other features that inquiry appears to require. This essay argues that the goddess’s arguments manifest something like a liar paradox: (...) She demonstrates on the basis of the opinions of mortals that mortals’ opinions are flawed. If so, then the goddess’s arguments do not establish that what-is is one and unchanging. What they show is that what inquiry and inference seem to require, given the opinions of mortals, is at odds with itself. To refer to what-is is to make aletheia impossible to reach. To be mortal, for Parmenides, is to journey through that incompleteness. (shrink)

In this paper, we discuss a family of arguments that show the inconsistency of the concept of omniscience, which is one of the central attributes of the theistic God. We introduce three member of this family: Grim’s Divine Liar Paradox, Milne’s Paradox and our own Divine Curry. They can be seen as theological counterparts of well-known semantic paradoxes. We argue that the very simple dialetheist response to these paradoxes doesn’t work well and then introduce our own response based on (...) a framework that we call Logic of Impossible Truths. LIT is a non-dialetheist paraconsistent logic designed to represent divine ominiscience and to preserve the transparency of the truth predicate and which semantics rests on the concept of situation. Since some rules of classical logic are not valid in LIT, we are in a position to block the derivation of the paradoxes. Thus, LIT offers a way out of the dilemma of accepting that there are true contradictions or giving up the idea that there is an all-powerful, omniscient and perfectly good being. (shrink)

My task here is the first one. I do present a consistent formal system and claim that it provides a perfect model of natural languages such as English, but this system involves no surprises. It is none other than the standard framework of classical logic and model theory. The real weight of the argument lies in the claim that the classical framework—without alteration or addition—contains the resources to model what happens when we say in English ‘This sentence is not (...) true’. (shrink)

In 1993, the American logic S. Yablo was proposed an original infinitive formulation of the classical ≪Liar≫ paradox. It questioned the traditional notion of self-reference as the basic structure for semantic paradoxes. The article considers the arguments underlying two different approaches to analysis of proposals of the ≪Infinite Liar≫ and understanding of the genuine sources for semantic paradoxes. The first approach (V. Valpola, G.-H. von Wright, T. Bolander, etc.) imposes responsibility for the emergence of semantic paradoxes on the (...) negation of the truth predicate. It deprives the ≪Infinite Liar≫ sentences of consistent truth values. The second approach is based on a modified version of anaphoric prosententialism (D. Grover, R. Brandom, etc.). The concepts of truth and falsehood are treated as special anaphoric operators. Logical constructs similar to the ≪Infinite Liar≫ do not attribute any definite truth values to sentences from which they are composed, but only state certain types of relations between the semantic content of such sentences. (shrink)

A number of theorists hold that literal, linguistic meaning is determined by the cognitive mechanism that underpins semantic competence. Borg and Larson and Segal defend a version of the view on which semantic competence is underpinned by the cognition of a truth-conditional semantic theory—a semantic theory which is true. Let us call this view the “cognitivist account of meaning”. In this paper, I discuss a surprisingly serious difficulty that the cognitivist account of meaning faces in light of the liar (...) paradox. I raise an argument to the effect that, in light of linguistic evidence concerning the liar paradox, the cognised semantic theory is inconsistent. This contradicts the cognitivist account. I consider a range of possible responses to the difficulty, raising problems for each. The liar paradox poses a serious difficulty to the cognitivist account of meaning, and it is unclear whether the difficulty can be resolved. (shrink)

Is the set of all self-membered sets, S, a member of itself? In naive set theory, this is Russell’s hypodox. By the Laws of Excluded Middle and Non-contradiction, S is a member of itself xor it is not, but no principle of classical logic or naive set theory determines which. (Herein, ‘xor’ extends English with a specifically exclusive disjunction.) As a hypodox, the Truth-teller is a sentence that says of itself simply that it is true; by the above mentioned principles, (...) the Truth-teller is true xor not true, but no principle of classical logic or naive truth determines which. Many concepts that have paradoxes have related hypodoxes, although the focus here is on these two. I argue that the Truth-teller does not rely on a principle of truth, in particular it does not rely on the T-schema. I also argue that Russell’s hypodox does not rely on Comprehension. Yet I relate Russell’s paradox and hypodox based on involution functions. The Liar and the Truth-teller are also related by means of involutions. Relations based on these involution functions can be represented in duality squares. Although hypodoxes are not paradoxes, these involution functions and duality relations warrant some commonality in a correct solution to a paradox and its dual hypodox. Using this and some other premises, I provide novel arguments supporting non-classical solutions for the Liar paradox and the significance of Russell’s hypodox for solutions to Russell’s paradox. (shrink)

We discuss misinformation about “the liar antinomy” with special reference to Tarski’s 1933 truth-definition paper [1]. Lies are speech-acts, not merely sentences or propositions. Roughly, lies are statements of propositions not believed by their speakers. Speakers who state their false beliefs are often not lying. And speakers who state true propositions that they don’t believe are often lying—regardless of whether the non-belief is disbelief. Persons who state propositions on which they have no opinion are lying as much as those (...) who state propositions they believe to be false. Not all lies are statements of false propositions—some lies are true; some have no truth-value. People who only occasionally lie are not liars: roughly, liars repeatedly and habitually lie. Some half-truths are statements intended to mislead even though the speakers “interpret” the sentences used as expressing true propositions. Others are statements of propositions believed by the speakers to be questionable but without revealing their supposed problematic nature. The two “formulations” of “the antinomy of the liar” in [1], pp.157–8 and 161–2, have nothing to do with lying or liars. The first focuses on an “expression” Tarski calls ‘c’, namely the following. -/- c is not a true sentence -/- The second focuses on another “expression”, also called ‘c’, namely the following. -/- for all p, if c is identical with the sentence ‘p’, then not p -/- Without argumentation or even discussion, Tarski implies that these strange “expressions” are English sentences. [1] Alfred Tarski, The concept of truth in formalized languages, pp. 152–278, Logic, Semantics, Metamathematics, papers from 1923 to 1938, ed. John Corcoran, Hackett, Indianapolis 1983. -/- https://www.academia.edu/12525833/Sentence_Proposition_Judgment_Statement_and_Fact_Speaking_about_th e_Written_English_Used_in_Logic. (shrink)

Fin dall’antichità esiste una tensione tra filosofia e letteratura, a cui David Hume ha dato voce dicendo che i poeti sono «mentitori per professione»: i testi letterari, in quanto opere di finzione che parlano di persone che non sono mai esistite e di eventi che non sono mai accaduti, non contengono proposizioni vere. Ciò implica, però, che essi sono privi di qualsiasi valore cognitivo. Questo articolo cerca di mostrare che tale atteggiamento anticognitivista si basa su una concezione errata del progresso (...) cognitivo, che lo riduce a un accumulo di dati. Quando apprendiamo da un testo letterario, invece, è perché esso ci offre nuove prospettive, approfondisce la nostra comprensione o ci invita a riflettere e ad arrivare a conclusioni nostre.There is an old tension between philosophy and literature that has been brought to the point by David Hume who stated that poets are «liars by profession». Literary texts, as works of fiction that talk about people who have never lived and events that have never taken place, do not contain true propositions and hence do not have any cognitive value. This article aims to show that the anticognitivistic argument is based on a false conception of cognitive progress, which reduces learning to the acquisition of information. We can learn from literary texts, however, because they offer new perspectives, deepen our understanding and invite us to reflect and arrive at our own conclusions. (shrink)

In Formale Logik, published in 1956, J. M. Bocheński presented his first proposal for the solution to the liar paradox, which he related to Paul of Venice's argumentation from Logica Magna. A formalized version of this solution was then presented in Formalisierung einer scholastischen Lösung der Paradoxie des ‘Lügners’ in 1959. The historical references of the resulting formalism turn out to be closer to Albert de Saxon's argument and the later solution by John Buridan. Bocheński did not pose (...) the question of the consistency of his theory. The case was taken up by B. Sobociński in his private letter to Bocheński from 12 August 1954. Sobociński used a smart translation of the language of Bocheński's theory into the classical propositional language with the notions of truth and falsehood inverted. The translation preserves the structure of the formalized solution. We explore Sobociński's idea and reconstruct his original proof. (shrink)

The Honest Life of a Liar By: Natalie Schweiger In the chapters of The Honest Life of a Liar, you will find humor, heartbreak, healing and adventure. It is one girl’s story of growing up, moving out, and learning about honesty in the real world. From parental arguments and hard lessons on love, to wacky landlords and Rocky Mountain highs, these pages hold something relatable for everybody. That girl, the author of this book, wants to share her story (...) not because it's monumental, will spark life change, or tell how she found the Atlantis, but because it involves experiences everyone has gone through, or is going through, in one way or another. She wants readers to close the back cover and feel like they've gained a friend; someone to ask advice on what to get their mom for Christmas or trust to be an escape call on a bad first date. Indeed, she wants readers to sit back and think "now that was a good story.". (shrink)

One of Marx‘s and Engels‘ main claims (hereafter ―original Marxism) in their account of the historical ―inevitability of the collapse of capitalism is that one‘s material (economic) conditions, not one‘s ideas, arguments or philosophy, determines one‘s ―consciousness and actions. However, the self-reference in this characterization of philosophical views generates a paradox analogous to the 7th century B.C. Epimenides ―Liar paradox. The Epimenides-paradox arises when Epimenides, a Cretan, states that all Cretans are liars. Epimenides-statement is paradoxical in the sense that (...) if it is true then it is false. Similarly, the Marxist claim that all philosophers who purport to state the cause of all social changes must be wrong, where Marx and Engels are themselves philosophers stating just such a claim, generates a paradox analogous to the ― Epimenides Liar paradox. This leads to what Engels himself calls a―false consciousness, i.e., a failure to understand the true causes of social change. This paradox can only be escaped by abandoning at least one of original Marxism‘s core doctrines. (shrink)

An important trend in contemporary metaphysics denies that the structure of natural language is an important datum for investigating fundamental structure. Ted Sider proceeds on this basis to propose a metaphysical semantics for natural language. Within this framework he argues that natural language and a fundamental, ‘jointcarving’, language could be subject to distinct logics. Developing an argument of Hartry Field’s, I show that Sider’s preferred option of fundamental classicality combined with non-fundamental non-classicality trivialises within the framework of Siderian metaphysical (...) semantics. The position can be saved only by revising key claims about truth and metaphysical semantics. This has serious implications for methdology in the metaphysics of logic. (shrink)

Recent interest in non-well-founded set theories has been concentrated on Aczel's anti-foundation axiom AFA. I compare this axiom with some others considered by Aczel, and argue that another axiom, FAFA, is superior in that it gives the richest possible universe of sets consistent with respecting the spirit of extensionality. I illustrate how using FAFA instead of AFA might result in an improvement to Barwise and Etchemendy's treatment of the liar paradox.

According to Peter Aczel, the inconsistency of Frege’s system in Grundgesetze is due, not to the introduction of sets, as is usually thought, but to the introduction of the Horizontal. His argument is that the principles governing sets are intuitively correct and therefore consistent, while the scheme introducing the Horizontal amounts to an internal definition of truth conflicting with Tarski’s classic result on the undefinability of truth in the object language. The aim of this paper is to show that (...) the Horizontal is innocent: Aczel’s diagnosis is based on a mistaken view of the structure underlying Frege’s ideal language. (shrink)

I argue that the paradoxes attributed to the Megarians, namely the Liar, the Sorites, presupposition ("Have you stopped beating your father,") and failure of substitution of co-referential terms in psychological verbs ("The Electra") were intended to be reasons to accept Parmenides view that non-being is an incoherent notion and that there is exactly One Being. That is, Eubulides and others were akin to Zeno, in indirectly supporting Parmenidean monism.

Scientific research in the formal sciences comes in multiple degrees of formality: fully formal work; rigorous proofs that practitioners know to be formalizable in principle; and informal work like rough proof sketches and considerations about the advantages and disadvantages of various formal systems. This informal work includes informal and semi-formal debates between formal scientists, e.g. about the acceptability of foundational principles and proposed axiomatizations. In this paper, we propose to use the methodology of structured argumentation theory to produce a formal (...) model of such informal and semi-formal debates in the formal sciences. For this purpose, we propose ASPIC-END, an adaptation of the structured argumentation framework ASPIC+ which can incorporate natural deduction style arguments and explanations. We illustrate the applicability of the framework to debates in the formal sciences by presenting a simple model of some arguments about proposed solutions to the Liar paradox, and by discussing a more extensive—but still preliminary—model of parts of the debate that mathematicians had about the Axiom of Choice in the early twentieth century. (shrink)

This is a reply to B. H. Slater's article "Liar Syllogisms and Related Paradoxes" (Analysis 51, 146-153), which raised an objection to one of the arguments considered in my article "Liar Syllogisms" (Analysis 50, 1-7). Slater's objection is shown to be a failure. In effect, the paradoxicality of liar syllogisms is vindicated.

The proposition that Jesus was ‘Bad, Mad or God’ is central to C.S. Lewis's popular apologetics. It is fêted by American Evangelicals, cautiously endorsed by Roman Catholics and Protestants, but often scorned by philosophers of religion. Most, mistakenly, regard Lewis's trilemma as unique. This paper examines the roots of this proposition in a two thousand year old theological and philosophical tradition (that is, aut Deus aut malus homo), grounded in the Johannine trilemma (‘unbalanced liar’, or ‘demonically possessed’, or ‘the (...) God of Israel come amongst his people’). Jesus can only be understood in the context of the Jewish religious categories he was born into; therefore, for Lewis, Jesus is who he reveals himself to be. Jesus' self-understanding reflects his identity, his triune salvific role; this is for Lewis, the transposed reality of divine Sonship. Reason and logic are paramount here, reflected in the structure of Lewis's argument. Lewis's trilemma is not so much a proof of God's existence, but a question, a dilemma, where each and every person must come to a decision. For all its perceived faults, its simplistic language, Lewis's trilemma still is a very successful piece of Christian apologetic, grounded in a serious philosophical and theological tradition. (shrink)

$${{{\mathcal {F}}}}$$ -systems are useful digraphs to model sentences that predicate the falsity of other sentences. Paradoxes like the Liar and the one of Yablo can be analyzed with that tool to find graph-theoretic patterns. In this paper we studied this general model consisting of a set of sentences and the binary relation ‘ $$\ldots $$ affirms the falsity of $$\ldots $$ ’ among them. The possible existence of non-referential sentences was also considered. To model the sets of all (...) the sentences that can jointly be valued as true we introduced the notion of conglomerate, the existence of which guarantees the absence of paradox. Conglomerates also enabled us to characterize referential contradictions, i.e., sentences that can only be false under a classical valuation due to the interactions with other sentences in the model. A Kripke-style fixed-point characterization of groundedness was offered, and complete (meaning that every sentence is deemed either true or false) and consistent (meaning that no sentence is deemed true and false) fixed points were put in correspondence with conglomerates. Furthermore, argumentation frameworks are special cases of $$\mathcal{F}$$ -systems. We showed the relation between local conglomerates and admissible sets of arguments and argued about the usefulness of the concept for the argumentation theory. (shrink)

Dissoi Logoi 4.6 presents a beautiful self-refutation argument, which I analyse here, offering a different assessment of its relation to self-contradiction and the Liar paradox from the only one available in the literature.