Epistemology of Logic

We present a philosophical motivation for the logics of formal inconsistency, a family of paraconsistent logics whose distinctive feature is that of having resources for expressing the notion of consistency within the object language. We shall defend the view according to which logics of formal inconsistency are theories of logical consequence of normative and epistemic character. This approach not only allows us to make inferences in the presence of contradictions, but offers a philosophically acceptable account of paraconsistency.

Boghossian (1996) has put forward an interesting explanation of how we can acquire logical knowledge via implicit definitions that makes use of a special template. Ebert (2005) has argued that the template is unserviceable, as it doesn't transmit warrant. In this paper, we defend the template. We first suggest that Jenkins (2008)’s response to Ebert fails because it focuses on doxastic rather than propositional warrant. We then reject Ebert’s objection by showing that it depends on an implausible and incoherent assumption.

The aim of this paper is threefold. Firstly, §1 and §2 introduce the novel concept logical akrasia by analogy to epistemic akrasia. If successful, the initial sections will draw attention to an interesting akratic phenomenon which has not received much attention in the literature on akrasia (although it has been discussed by logicians in different terms). Secondly, §3 and §4 present a dilemma related to logical akrasia. From a case involving the consistency of Peano Arithmetic and Gödel’s Second Incompleteness Theorem (...) it’s shown that either we must be agnostic about the consistency of Peano Arithmetic or akratic in our arithmetical theorizing. If successful, these sections will underscore the pertinence and persistence of akrasia in arithmetic (by appeal to Gödel’s seminal work). Thirdly, §5 concludes by suggesting a way of translating the dilemma of arithmetical akrasia into a case of regular epistemic akrasia; and further how one might try to escape the dilemma when it’s framed this way. (shrink)

Recently an abductivist approach to the epistemology of logic has gained traction. A necessary component of logical abductivism is justification holism, asserting that claims of logical entailment can only be justified in the context of an entire logical theory, e.g., classical, intuitionistic, etc. One view that is incompatible with abductivism is an atomistic view on which individual entailment-claims can be justified point-wise rather than in the context of a whole theory. This paper provides two atomistic counterexamples to justification holism in (...) the epistemology of logic. Both examples appeal to pre-theoretic commitments of deductive validity. The main aim is to show that there are some foundational entailment-claims for which we can have propositional justification independently of theory choice and outside the context of a whole logical theory. If one were to give up on these foundational claims, all semantic and syntactic accounts of deductive validity would be non-starters. (shrink)

Anti‐exceptionalism about logic is the view that logic is not special; it is just like empirical sci‐ ence in many respects. In particular, it is thought that an anti‐exceptionalist must also hold that logical theories are completely a posteriori. However, it is not clear what it means to say that logical theories are a posteriori, for the a priori/a posteriori divide has been explored from different perspectives in contemporary philosophy. The central claim of this paper is to argue that logical (...) anti‐exceptionalism is quite compatible with the a priori, if the a priori/a posteriori divide is understood in the lines recently developed by Tuomas Tahko. The con‐ ception advanced by Tahko is characterized by an interplay between a priori and a posteriori knowledge, generating a bootstrapping relation in which one kind of knowledge constantly substantiates the other. We further present some of the advantages of the bootstrapping approach over the current epistemology associated with anti‐exceptionalism. (shrink)

By a reasoned change in logic I mean a change in the logic with which you make inferences that is based on your evidence. An argument sourced in recently published material Kripke lectured on in the 1970s, and dubbed the Adoption Problem by Birman (then Padró) in her 2015 dissertation, challenges the possibility of reasoned changes in logic. I explain why evidentialists should be alarmed by this challenge, and then I go on to dispel it. The Adoption Problem rests on (...) a failure to distinguish between logical principles such as Universal Instantiation and Modus Ponens which might or might not govern your inferences with superficially similar laws which must govern your cognitive architecture. (shrink)

What is commonly referred to as the Adoption Problem is a challenge to the idea that the principles of logic can be rationally revised. The argument is based on a reconstruction of unpublished work by Saul Kripke. As the reconstruction has it, Kripke extends the scope of Willard van Orman Quine's regress argument against conventionalism to the possibility of adopting new logical principles. In this paper we want to discuss the scope of this challenge. Are all revisions of logic subject (...) to the Adoption Problem? If not, are there significant cases of logical revision that are subject to the Adoption Problem? We will argue that both questions should be answered negatively. (shrink)

This paper develops a novel approach to the question of the normativity of logic, which we reinterpret as a clash between two intuitions: the direct normativity intuition and the unfeasibility intuition. The standard response has been to dismiss the direct normativity intuition, bridging logic and reasoning via principles that relativize the normative import of logic to pragmatic and feasibility considerations. We argue that the standard response is misguided. Building upon theories of bounded rationality, our approach conceptualizes reasoning as constrained by (...) multiple, independent normative factors, logical and non-logical ones. These different factors can conflict with one another, to the effect that logically sound inferences might not coincide with what is feasible for an agent to infer. From this perspective, we will argue that logic gives us only prima facie, i.e. contributive and defeasible, obligations on what to believe, but that such obligations do not always coincide with what an agent ought to believe all things considered. These distinctions will dissolve the alleged clash between the direct normativity and the unfeasibility intuition. (shrink)

I argue that logic is unlike science in its methodology, thus rejecting anti-exceptionalism about logic. Logic has a mathematical and a philosophical part. In its mathematical part, the methodology of logic is like that of mathematics, and no need to choose between theories arises in that part. In its philosophical part, the methodology of logic is like that of philosophy. Philosophy and mathematics are both unlike the empirical sciences in their methodology. So logic is unlike the empirical sciences in its (...) methodology. I end by looking at disagreements about the liar paradox as an example. (shrink)

The notion of strength has featured prominently in recent debates about abductivism in the epistemology of logic. Following Williamson and Russell, we distinguish between logical and scientific strength and discuss the limits of the characterizations they employ. We then suggest understanding logical strength in terms of interpretability strength and scientific strength as a special case of logical strength. We present applications of the resulting notions to comparisons between logics in the traditional sense and mathematical theories.

The article recapitulates what logic is about traditionally and works out two roles it has been playing in philosophy: the role of an instrument and of a philosophical discipline in its own right. Using Tarski’s philosophical-logical work as case study, it develops a logical reconstructionist methodology of philosophical logic that extends and refines Rudolf Carnap’s account of explication and rational reconstruction. The methodology overlaps with, but also partially diverges from, contemporary anti-exceptionalism about logic.

Philosophers of logic are particularly interested in understanding the aims, epistemology, and methodology of logic. This raises the question of how the philosophy of logic should go about these enquires. According to the practice-based approach, the most reliable method we have to investigate the methodology and epistemology of a research field is by considering in detail the activities of its practitioners. This holds just as true for logic as it does for the recognised empirical and abstract sciences. If we wish (...) to systematically understand the aims and epistemology of logic, we are best placed achieving this by looking at what logicians do, rather than reflecting upon the nature of logic itself. In this entry, we outline the motivations for a practice-based approach towards the philosophy of logic and highlight its advantages over more “top-down” approaches, which attempt to infer conclusions about the nature of logic and its methodology on the basis of traditional assumptions about knowledge, metaphysics, or logic itself. We end by addressing several prominent concerns raised against the practice-based approach. (shrink)

This paper argues that inference rule adoption is a diachronic process during which agents are inferentially guided by a statement of the rule they are adopting, but during which they do not use that rule. Rather, the ability to use the rule is the outcome at the end of the process. This account avoids a regress objection to inferentially guided adoption recently posed by Boghossian and Wright. Adoption, on this model, involves the use of six privileged inference rules, including universal (...) instantiation, modus ponens, and the naive truth rules. However, though these rules play a special role in adoption, they are not indispensable to the process in their full generality: so long as one has reasonably robust restrictions of them, the adoption process is unimpeded. Furthermore, there are no general forms that constitute the minimal restrictions of these rules required for adoption. It follows that these rules, in their fully generality, are themselves adoptable, so long as one begins with reasonable restrictions of them. It is argued that this is enough to overcome the ‘adoption problem’ as a challenge to anti-exceptionalism about logic and to the normative significance of proposals for alternative logics. (shrink)

Anti-exceptionalists about formal logic think that logic is continuous with the sciences. Many philosophers of science think that there is feminist science. Putting these together: can anti-exceptionalism make space for feminist logic? The answer depends on the details of the ways logic is like science and the ways science can be feminist. This paper wades into these details, examines five different approaches, and ultimately argues that anti-exceptionalism makes space for feminist logic in several different ways.

This paper critically examines logical instrumentalism as it has been put forth recently in the anti-exceptionalism about logic debate. I will argue that if one wishes to uphold the claim that logic is significantly similar to science, as the anti-exceptionalists have it, then logical instrumentalism cannot be what previous authors have taken it to be. The reason for this, I will argue, is that as the position currently stands, first, it reduces to a trivial claim about the instrumental value of (...) logical systems, and second, by its denial that logic aims to account for extra-systemic phenomena it significantly differs from science, in contrast with the AEL agenda. I will conclude by proposing a different kind of logical instrumentalism that I take to have a broad appeal, but especially for anti-exceptionalists, for it is developed as analogous to—and thus much closer aligned with—scientific instrumentalism. (shrink)

In the philosophy of logic, the Adoption Problem is a challenge to the claim that reasoners can, in certain ways, rationally change which logic they use. The (alleged) problem is that if someone does not already infer in accordance with some fundamental logical principles (such as Universal Instantiation or Modus Ponens), then they cannot rationally begin to do so: the “adoption” of these principles is either unnecessary or impossible. In the literature, three issues have emerged as especially contentious: (1) How (...) should we understand the argument for the Adoption Problem? What exactly is the argument’s conclusion, and how is it established, if at all? (2) How could someone who thinks that the rational adoption of logic is possible respond to the Adoption Problem? (3) What are the consequences of the Adoption Problem for related issues in the philosophy of logic? In this paper, we address each question in turn. We suggest that the Adoption Problem is best understood in the form of an inconsistent quartet of theses regarding logical inference. We classify positions on logical adoption in terms of which of these theses is abandoned, and we show that such a taxonomy of positions is useful for delineating the scope and consequences of the Adoption Problem. (shrink)

This Element delves into the relationship between logic and the sciences, a topic brought to prominence by Quine, who regarded logic as methodologically and epistemologically akin to the sciences. For this reason, Quine is seen as the forefather of anti-exceptionalism about logic (AEL), a stance that has become prevalent in the philosophy of logic today. Despite its popularity and the volume of research it inspires, some core issues still lack clarity. For one thing, most works in the debate remain vague (...) on what should count as logic and what should count as a science. Furthermore, the terms of the comparison are rarely specified and discussed in a systematic way. This Element purports to advance the debate on these crucial issues with the hope of fostering our understanding of the fundamentals of AEL. (shrink)

While the epistemic significance of disagreement has been a popular topic in epistemology for at least a decade, little attention has been paid to logical disagreement. This monograph is meant as a remedy. The text starts with an extensive literature review of the epistemology of (peer) disagreement and sets the stage for an epistemological study of logical disagreement. The guiding thread for the rest of the work is then three distinct readings of the ambiguous term ‘logical disagreement’. Chapters 1 and (...) 2 focus on the Ad Hoc Reading according to which logical disagreements occur when two subjects take incompatible doxastic attitudes toward a specific proposition in or about logic. Chapter 2 presents a new counterexample to the widely discussed Uniqueness Thesis. Chapters 3 and 4 focus on the Theory Choice Reading of ‘logical disagreement’. According to this interpretation, logical disagreements occur at the level of entire logical theories rather than individual entailment-claims. Chapter 4 concerns a key question from the philosophy of logic, viz., how we have epistemic justification for claims about logical consequence. In Chapters 5 and 6 we turn to the Akrasia Reading. On this reading, logical disagreements occur when there is a mismatch between the deductive strength of one’s background logic and the logical theory one prefers (officially). Chapter 6 introduces logical akrasia by analogy to epistemic akrasia and presents a novel dilemma. Chapter 7 revisits the epistemology of peer disagreement and argues that the epistemic significance of central principles from the literature are at best deflated in the context of logical disagreement. The chapter also develops a simple formal model of deep disagreement in Default Logic, relating this to our general discussion of logical disagreement. The monograph ends in an epilogue with some reflections on the potential epistemic significance of convergence in logical theorizing. (shrink)

Logical realism is the metaphysical view asserting that the facts of logic exist and are mind-and-language independent. McSweeney argues that if logical realism is true, we encounter a dilemma. Either we cannot determine which of the two logically equivalent theories holds a fundamental status, or neither theory can be considered fundamental. These two conclusions together constitute what is known as the _Unfamiliarity Dilemma_, which poses significant challenges to our understanding of the epistemological and metaphysical features of logic. In this article, (...) I present two strategies to address McSweeney’s dilemma. If these arguments prove effective, they would demonstrate that our knowledge of logic is not susceptible to the skeptical concerns raised by McSweeney’s hypothesis. (shrink)

Thomas Hofweber takes the semantic paradoxes to motivate a radical reconceptualization of logical validity, rejecting the idea that an inference rule is valid just in case every instance thereof is necessarily truth-preserving. Rather than this “strict validity”, we should identify validity with “generic validity”, where a rule is generically valid just in case its instances are truth preserving, and where this last sentence is a generic, like “Bears are dangerous”. While sympathetic to Hofweber’s view that strict validity should be replaced (...) by something allowing for exceptions, I argue that this should instead be truth-conduciveness, a matter of a large majority of instances being truth-preserving. The fact that inference rules have uncountably many instances, I argue, can be handled by defining truth-conduciveness as relative to finite sets of instances. Moreover, I argue that Hofweber’s position, while seemingly radical, may be less so under closer scrutiny. For the mere claim that classical rules and unrestricted truth rules are generically valid (or truth-conducive) is not in itself controversial. Also, if there is an answer to the question of which of these are also strictly valid, then the claim that generic validity is the central notion in logic is at most an interest-relative matter, since there is then also a fact of the matter as to which inference rules are (not) strictly valid. If no solution operating with strict validity to the paradoxes can be had, however, then the claim that validity should be identified with a weaker notion is better motivated. I argue that it is reasonable, in view of past failures, to conjecture that no ordinary solution will score high enough relative to standard (uncontroversial) desiderata to merit justified belief. Hence, it is unknowable which solution is correct. I further argue that this is best explained by its being metaphysically indeterminate which solution is correct. If this conjecture is true, then we ought instead to think of validity as allowing exceptions, and then take the “true logic” to be one that takes both the classical rules and the truth rules to be valid, i.e., truth-conducive. This logic scores very high on the desiderata on logics, and is therefore preferable to any logic operating with strict validity. (shrink)

Logical abductivism features in the recent literature as a _new epistemology_ for logic, in connection with logical anti-exceptionalism. According to this account, (i) logical knowledge is obtained by the justified _choice_ of a logical theory using abduction, which (ii) _replaces_ problematic approaches in traditional logical epistemology. We argue that such claims are not properly warranted; they conflate justification and theory choice methods. Abduction requires that one starts with _justified data_, and justification, in such cases, needs to appeal to sources that (...) are not granted by abduction. In this sense, abduction cannot be all there is to the epistemology of logic. Some abductivists, we shall see, even appeal to methods of the traditional epistemology to obtain the data. Keeping justification and theory choice separated may contribute to avoid obscurities in discussion of the nature of data in logic and in understanding more clearly how to frame the anti-exceptional nature of logic. (shrink)

Logical inferentialism maintains that the formal rules of inference fix the meanings of the logical terms. The categoricity problem points out to the fact that the standard formalizations of classical logic do not uniquely determine the intended meanings of its logical terms, i.e., these formalizations are not categorical. This means that there are different interpretations of the logical terms that are consistent with the relation of logical derivability in a logical calculus. In the case of the quantificational logic, the categoricity (...) problem is generated by the finite nature of the standard calculi and one direction in which it can be solved is to strengthen the deductive systems by adding infinitary rules (such as the ω-rule), i.e., to construct a full formalization. Another main direction is to provide a natural semantics for the standard rules of inference, i.e., a semantics for which these rules are categorical. My aim in this paper is to analyze some recent approaches for solving the categoricity problem and to argue that a logical inferentialist should accept the infinitary rules of inference for the first order quantifiers, since our use of the expressions “all” and “there is” leads us beyond the concrete and finite reasoning, and human beings do sometimes employ infinitary rules of inference in their reasoning. (shrink)

Logical inferentialism maintains that the formal rules of inference fix the meanings of the logical terms. The categoricity problem points out to the fact that the standard formalizations of classical logic do not uniquely determine the intended meanings of its logical terms, i.e., these formalizations are not categorical. This means that there are different interpretations of the logical terms that are consistent with the relation of logical derivability in a logical calculus. In the case of the quantificational logic, the categoricity (...) problem is generated by the finite nature of the standard calculi and one direction in which it can be solved is to strengthen the deductive systems by adding infinitary rules (such as the ω-rule), i.e., to construct a full formalization. Another main direction is to provide a natural semantics for the standard rules of inference, i.e., a semantics for which these rules are categorical. My aim in this paper is to analyze some recent approaches for solving the categoricity problem and to argue that a logical inferentialist should accept the infinitary rules of inference for the first order quantifiers, since our use of the expressions “all” and “there is” leads us beyond the concrete and finite reasoning, and human beings do sometimes employ infinitary rules of inference in their reasoning. (shrink)

This paper examines the conceptions of logic from Leibniz, Hume, Kant, Frege, Wittgenstein and Ayer, and regards the six philosophers as the representatives of logical exceptionalism. From their standpoints, this paper refines the tenets of logical exceptionalism as follows: logic is exceptional to all other sciences because of four reasons: (i) logic is formal, neutral to any domain and any entities, and general; (ii) logical truths are made true by the meanings of logical constants they contain or by logicians' rational (...) insight to consequence relations; (iii) logical truths are analytical, a prior and necessary, so not‐revisable; and (iv) logical laws are normative for how to correctly think. However, logical exceptionalism has encountered difficult open problems: What are logical constants? How to justify basic laws of logic? How are logical laws accessible to us? How to explain the reasonability of rival logics and select from them? How to explain the universal applicability of logical laws? How to explain the normativity of logical laws for correct thinking? This paper concludes that logical anti‐exceptionalism is more hopeful to successfully answer these questions than logical exceptionalism. (shrink)

Recent approaches to the epistemology of logic, under the title of “anti-exceptionalism about logic”, explicitly adopt what is asserted to be the method of theory choice and the correct account of explanation in the sciences. Without embracing such a doctrine, but still keeping within a broad anti-exceptional trend, the current discussion proposes a contextual theory of explanation in logic, based on Bas van Fraassen’s framework of why-questions, which neither claims that logic is a science, nor relies on the metaphysical assumption (...) of a validity-phenomenon to give account of the methodology of logic. (shrink)

I analyze Peirce’s reply in the 1903 Lowell Lectures to the “defendant argument” and show how his response provides a key to interpreting his later philosophy of logic and his views on the normative role of deductive logic in inquiry. I argue that in Peirce’s discussion of self-control in reasoning and evaluation of reasoning, we find an underappreciated position on logical revision and how to understand rational choice between deductive theories. To defend this point, I reconstruct Peirce’s reply by providing (...) an interpretation of his comments on higher-order criticism and the soundness of our reasoning, arguing that the resulting position’s ability to separate questions involving the role of logic in inquiry from questions better suited to the mathematical study of a logical theory provides a fruitful pragmatist reframing of problems in the epistemology of logic. (shrink)

In this paper, I outline a pragmatist epistemology of logic inspired by later work of Charles S. Peirce that shares many features with an anti-exceptionalism about logic but, I argue, can better respond to a key problem that plagues the anti-exceptionalist. I first lay out what I take to be the tenets of anti-exceptionalism, discussing some difficulties in formulating the position that make it difficult to definitively label the position discussed here. I then analyze a key problem for the anti-exceptionalist, (...) the background logic problem, and suggest that when framed as a problem for certain types of inquiry, it shares a presupposition about the priority of logic with other problems in the epistemology of logic. Turning to a discussion of Peirce from the 1903 Lowell Lectures, I then outline a pragmatism about logic that rejects the priority claims underlying the problems for inquiry in logic and, I argue, can resolve the background logic problem. (shrink)

The Adoption Problem (AP) was a postponed issue for some years (Kripke, 2024; Padró, 2015; Birman, 2024). This problem highlights certain difficulties surrounding the adoption of rules of inference: If anti-exceptionalism is wrong, is it possible to adopt an alternative logic? What is the point of the revision of logic in epistemology? During 2022 Kripke, Padró and Barrio held seminars on AP. The latter two edited the first thematic section on this subject in the journal Análisis Filosófico. It contains “What (...) the Adoption Problem Does Not Show” by Camilo Fiore, subject of this critical note, in which Fiore holds two theses: 1) AP is compatible with the thesis that logica utens is revisable; 2) to assess whether an agent can revise their logic, it is best to consider a different definition of adoption, e.g. weak adoption, according to which Universal Instantiation and Modus Ponens are sometimes adoptable. It then states that (1) and (2) are independent. In this article I will criticize the independence between (1) and (2). To this end, I will point out that thesis (1) and (2) are supported by the examples of Carrie and Barry, respectively, and that the type of logical revision involved in both is the same and local. Therefore, (1) and (2) are not independent. Next, I argue that it is impossible to satisfy another kind of logical revision, e.g. global revision. Therefore, the interdependence between (1) and (2) is not due to the examples proposed. (shrink)

Philosophy and Phenomenological Research, EarlyView.

According to anti-exceptionalism about logic (AEL), logic is not as exceptional in terms of its epistemology and subject matter as has been conventionally thought. Whereas logic's epistemology has often been considered distinct from those of the recognised sciences, in virtue of being both non-inferential and a priori, it is in fact neither. Logics are justified on the basis of similar mechanisms of theory-choice as theories in the sciences, and further the sources of evidence which inform these theory choices are (at (...) least) not wholly a priori. In this first part of a two-part entry on AEL, we trace these epistemological elements of AEL back to Quine's naturalism and evidential holism, but then highlight important differences between the motivations and commitments of Quine's version of AEL and those within the contemporary literature. This demonstrates the need to assess contemporary anti-exceptionalist positions on their own merits, rather than treating them as mere reincarnations of Quine's evidential holism. (shrink)

This chapter responds to Saul Kripke’s critique of the idea of adopting an alternative logic. It defends an anti-exceptionalist view of logic, on which coming to accept a new logic is a special case of coming to accept a new scientific theory. The approach is illustrated in detail by debates on quantified modal logic. A distinction between folk logic and scientific logic is modelled on the distinction between folk physics and scientific physics. The importance of not confusing logic with metalogic (...) in applying this distinction is emphasized. Defeasible inferential dispositions are shown to play a major role in theory acceptance in logic and mathematics as well as in natural and social science. Like beliefs, such dispositions are malleable in response to evidence, though not simply at will. The chapter considers the Quinean objection that accepting an alternative logic involves changing the subject rather than denying the doctrine. The objection is shown to depend on neglect of the social dimension of meaning determination, akin to descriptivism about proper names and natural kind terms criticized by Kripke and Putnam. Normal standards of interpretation indicate that disputes between classical and non-classical logicians are genuine disagreements. (shrink)

This paper develops a new class of justification logic, the logic of epistemic entitlement. The logic of epistemic entitlement invokes the notion of epistemic entitlement in epistemology, and interprets a justification formula in the form of???? ∶???? as follows: the warrant???? entitles the agent to believe????. In the logic of epistemic entitlement, the formula???? ∶???? is true if and only if???? is true in all possible worlds entitled to be conceived by????. In contrast to the standard epistemic semantics of justification (...) logic, the formula???? ∶???? in Fitting’s model is true if and only if???? is true in all possible worlds that can be conceived of and satisfies the evidential condition: the epistemic state???? ∈ ℰ(????,????) that the epistemic agent is in. Thus, if???? is not a dead point in the model, the point model of???? cannot satisfy both formulas of the form???? ∶???? and????′∶ ¬????. Thus standard justification logic cannot characterize the conflicting beliefs of agents for different warrants. Instead, the logic of epistemic entitlement solves this problem by entitling agents to believe???? and ¬???? on two disjoint sets of possible worlds on????,???? and????′, respectively. ℳ,???? ⊩???? ∶???? if and only if ℳ,???? ⊩???? for every???? ∈????????????(????,????) with????????????. Such an epistemic entitlement in the paper is axiomatized into the logic J_???????????? and the validity of its axioms is verified. And a canonical model of J_???????????? is established to prove its completeness. Finally, extensions of J_???????????? are attempted to explore the logic of entitlement of belief J_EntD4 and logic of entitlement of knowledge J_EntT4. (shrink)

A key question in the philosophy of logic is how we have epistemic justification for claims about logical entailment (assuming we have such justification at all). Justification holism asserts that claims of logical entailment can only be justified in the context of an entire logical theory, e.g., classical, intuitionistic, paraconsistent, paracomplete etc. According to holism, claims of logical entailment cannot be atomistically justified as isolated statements, independently of theory choice. At present there is a developing interest in—and endorsement of—justification holism (...) due to the revival of an abductivist approach to the epistemology of logic. This paper presents an argument against holism by establishing a foundational entailment-sentence of deduction which is justified independently of theory choice and outside the context of a whole logical theory. (shrink)

By playing a crucial role in settling open issues in the philosophical debate about logical consequence, logical evidence has become the holy grail of inquirers investigating the domain of logic. However, despite its indispensable role in this endeavor, logical evidence has retained an aura of mystery. Indeed, there seems to be a great disharmony in conceiving the correct nature and scope of logical evidence among philosophers. In this paper, I examine four widespread conceptions of logical evidence to argue that all (...) should be reconsidered. First, I argue that logical apriorists are more tolerant of logical evidence than empiricists. Second, I argue that evidence for logic should not be read out of natural language. Third, I argue that if logical intuitions are to count as logical evidence, then their evidential content must not be propositional. Finally, I argue that the empiricist proposal of treating experts' judgments as evidence suffers from the same problems as the rationalist conception. (shrink)

After introducing the adoption problem (AP) as the claim that certain basic logical principles cannot be adopted, I offer a characterization of this notion as a two-phase process consisting in (1) the acceptance of a basic logical principle, and (2) the development, in virtue of Phase 1, of a practice of inferring in accordance with that principle. The case of a subject who does not infer in accordance with universal instantiation is considered in detail. I argue that the AP has (...) deep and wide implications for the epistemology of logic, extending well beyond Kripke’s original target, viz. Putnam’s proposal for the empirical revision of logic and its background Quinean epistemology. In particular, the AP questions whether basic logical principles could have a fundamental role in our inferential practices, drawing our attention to the nature of basic inferences and the need to have a clearer conception of them before taking a stand on the matter of the epistemic justification of the logical principles. (shrink)

Gideon Rosen, Brian Leiter, and Catarina Dutilh Novaes raise deep questions about the arguments in Morality and Mathematics (M&M). Their objections bear on practical deliberation, the formulation of mathematical pluralism, the problem of universals, the argument from moral disagreement, moral ‘perception’, the contingency of our mathematical practices, and the purpose of proof. In this response, I address their objections, and the broader issues that they raise.

Logicism is the thesis that all or, at least parts, of mathematics is reducible to deductive logic in at least two senses: (A) that mathematical lexis can be defined by sole recourse to logical constants [a definition thesis]; and, (B) that mathematical theorems are derivable from solely logical axioms [a derivation thesis]. The principal proponents of this thesis are: Frege, Dedekind, and Russell. The central question that I raise in this paper is the following: ‘How did Russell construe the philosophical (...) worth of logicism?’ The argument that I build in response to this is that Russell perceived an inverse proportion between a logical reduction of mathematics and the certitude of non-novel mathematical theorems—such that the more we reduce mathematics to logic, the more certain we become of our mathematical theorems; this was portrayed through a presentation of mathematical knowledge as coherent. Therefore, I set out to sketch Russell’s coherence theory and appraise it in relation to the presence discourse: i.e., in relation to logicism and mathematical certainty. (shrink)

Under the influence of Quine’s famous manifesto, many philosophers have thought that logical theories are scientific theories that can be ‘adopted’ and tested as scientific theories. Here we argue that this idea is untenable. We discuss it with special reference to Putnam’s proposal to ‘adopt’ a particular non-classical logic to solve the foundational problems of quantum mechanics in his famous paper ‘Is Logic Empirical?’ (1968), which we argue was not really coherent.

The historical consensus is that logical evidence is special. Whereas empirical evidence is used to support theories within both the natural and social sciences, logic answers solely to a priori evidence. Further, unlike other areas of research that rely upon a priori evidence, such as mathematics, logical evidence is basic. While we can assume the validity of certain inferences in order to establish truths within mathematics and test scientifi c theories, logicians cannot use results from mathematics or the empirical sciences (...) without seemingly begging the question. Appeals to rational intuition and analyticity in order to account for logical knowledge are symptomatic of these commitments to the apriority and basicness of logical evidence. This chapter argues that these historically prevalent accounts of logical evidence are mistaken, and that if we take logical practice seriously we fi nd that logical evidence is rather unexceptional, sharing many similarities to the types of evidence appealed to within other research areas. (shrink)

Drawing on the epistemology of logic literature on anti-exceptionalism about logic, we set out to investigate the following metaphilosophical questions empirically: Is philosophy special? Are its methods (dis)continuous with science? More specifically, we test the following metaphilosophical hypotheses empirically: philosophical deductivism, philosophical inductivism, and philosophical abductivism. Using indicator words to classify arguments by type (namely, deductive, inductive, and abductive arguments), we searched through a large corpus of philosophical texts mined from the JSTOR database (N = 435,703) to find patterns of (...) argumentation. The results of our quantitative, corpus-based study suggest that deductive arguments are significantly more common than abductive arguments and inductive arguments in philosophical texts overall, but they are gradually and steadily giving way to non-deductive (i.e. inductive and abductive) arguments in academic philosophy. (shrink)

Nancy Cartwright's 1983 book How the Laws of Physics Lie argued that theories of physics often make use of idealisations, and that as a result many of these theories were not true. The present paper looks at idealisation in logic and argues that, at least sometimes, the laws of logic fail to be true. That might be taken as a kind of skepticism, but I argue rather that idealisation is a legitimate tool in logic, just as in physics, and recognising (...) this frees logicians up to use false laws where these are helpful. (shrink)

The adoption question asks whether there are logical rules that cannot be adopted if one does not already infer in accordance with them. Several philosophers, most famously Saul Kripke and Romina Padró, agree that there are such rules. Accordingly, they agree that there is an adoption problem. However, there is disagreement over which rules are unadoptable. In particular, while most agree that if there is an adoption problem, modus ponens and universal instantiation are in its scope, many would exclude adjunction (...) from the list. In this paper, I argue that adjunction is in the scope of the adoption problem. Then I show that the most straightforward counterargument against adjunction being in the scope of the problem, which tries to reformulate the adjunction rule into a more palatable one, does not work. (shrink)

This paper puts forward a new account of rigorous mathematical proof and its epistemology. One novel feature is a focus on how the skill of reading and writing valid proofs is learnt, as a way of understanding what validity itself amounts to. The account is used to address two current questions in the literature: that of how mathematicians are so good at resolving disputes about validity, and that of whether rigorous proofs are necessarily formalizable.

This paper has three aims: first, to present in a clear way Newton da Costa’s argument against the necessity of logical laws. In order to do so, we need to clearly advance his views on the idea that logic is context-relative, and not known a priori. Doing so, however, requires that we present his methodology for the development of counter-examples to logical laws: the use of hypothetical models in logic. Given that this method has been overlooked in most discussions on (...) the epistemology of logic, our second goal is to present da Costa’s views on it carefully. The discussion of some tensions resulting from the relation of a system of logic and the context it governs, in da Costa’s approach, is our third goal. Basically, da Costa seems to swing between two incompatible views on such relation, requiring sometimes that a logic is dependent on a context, and in other cases, that the nature of the context is dependent on a logic. Bringing this to light may also benefit current discussions on logical relativism. (shrink)

In this paper, I discuss the relation between logical theory and evidence in the context of an anti-exceptionalist approach to logic. I hold not only that current versions of anti-exceptionalism failed to appreciate the fact that logical evidence is theory laden, but also that benefits for the view are expected when we engage with the appropriate philosophy of science. I make the discussion more vivid by considering the cases of both the Liar and Russell paradoxes, and disputes between the classical (...) and dialetheist approaches to them. Disputes between these parties involve different understandings of the logical terminology involved in the evidence (the paradoxes), and they illustrate how the data gets contaminated with theory. As a result of the discussion, I conclude that pragmatical considerations are better guides to evaluate disputes in such cases, with scientific fertility being the criterion of legitimacy for a logical system. (shrink)

Logical anti‐exceptionalism is the view that logic is not special, it is continuous with science. This continuity is typically understood in terms of the use of the abductive method in logical theory choice, with logical knowledge resulting from our choice of the theory best accounting for the data. In this paper, we argue for two related claims: (i) that this understanding of the continuity between logic and science faces considerable challenges; and (ii) that such challenges may be avoided by elaborating (...) the continuity of logic with science in terms of the “logic‐as‐models” approach. More specifically, we defend that logical theories should be seen in the lights of the “models‐as‐epistemic‐tools” approach, an approach to the nature of models in empirical science more closely connected with current scientific practice. The result is a version of logical anti‐exceptionalism opening new perspectives for the philosophical understanding of logic. (shrink)

Anti-exceptionalism about logic is the thesis that logic is not special. In this paper, I consider, and reject, a challenge to this thesis. According to this challenge, there are basic logical principles, and part of what makes such principles basic is that they are epistemically exceptional. Thus, according to this challenge, the existence of basic logical principles provides reason to reject anti-exceptionalism about logic. I argue that this challenge fails, and that the exceptionalist positions motivated by it are thus unfounded. (...) I make this case by disambiguating two senses of ‘basic’ and showing that, once this disambiguation is taken into account, the best reason we have for thinking that there are basic principles actually implies that those principles do not require a special epistemology. Consequently, the existence of basic logical principles provides reason to accept, rather than reject, anti-exceptionalism concerning the epistemology of logic. I conclude by explaining how an abductivist, anti-exceptionalist approach to the epistemology of logic can accommodate the notion of basic logical principles. (shrink)