Is logic normative for reasoning? In the wake of work by Gilbert Harman and John MacFarlane, this question has been reduced to: are there any adequate bridge principles which link logical facts to normative constraints on reasoning? Hitherto, defenders of the normativity of logic have exclusively focussed on identifying adequate validity bridge principles: principles linking validity facts—facts of the form 'gamma entails phi'—to normative constraints on reasoning. This paper argues for two claims. First, for the time being at least, Harman’s (...) challenge cannot be surmounted by articulating validity bridge principles. Second, Harman’s challenge can be met by articulating invalidity bridge principles: principles linking invalidity facts of the form 'gamma does not entail phi' to normative constraints on reasoning. In doing so, I provide a novel defence of the normativity of logic. (shrink)

The phenomenological movement begins in the Prolegomena to Husserl’s Logical Investigations as a philosophy of logic. Despite this, remarkably little attention has been paid to Husserl’s arguments in the Prolegomena in the contemporary philosophy of logic. In particular, the literature spawned by Gilbert Harman’s work on the normative status of logic is almost silent on Husserl’s contribution to this topic. I begin by raising a worry for Husserl’s conception of ‘pure logic’ similar to Harman’s challenge to explain the connection between (...) logic and reasoning. If logic is the study of the forms of all possible theories, it will include the study of many logical consequence relations; by what criteria, then, should we select one consequence relation as correct? I consider how Husserl might respond to this worry by looking to his late account of the ‘genealogy of logic’ in connection with Gurwitsch’s claim that ‘[i]t is to prepredicative perceptual experience … that one must return for a radical clarification and for the definitive justification of logic’. Drawing also on Sartre and Heidegger, I consider how prepredicative experience might constrain or guide our selection of a logical consequence relation and our understanding of connectives like implication and negation. (shrink)

I argue against abductivism about logic, which is the view that rational theory choice in logic happens by abduction. Abduction cannot serve as a neutral arbiter in many foundational disputes in logic because, in order to use abduction, one must first identify the relevant data. Which data one deems relevant depends on what I call one's conception of logic. One's conception of logic is, however, not independent of one's views regarding many of the foundational disputes that one may hope to (...) solve by abduction. (shrink)

(1) This paper is about how to build an account of the normativity of logic around the claim that logic is constitutive of thinking. I take the claim that logic is constitutive of thinking to mean that representational activity must tend to conform to logic to count as thinking. (2) I develop a natural line of thought about how to develop the constitutive position into an account of logical normativity by drawing on constitutivism in metaethics. (3) I argue that, while (...) this line of thought provides some insights, it is importantly incomplete, as it is unable to explain why we should think. I consider two attempts at rescuing the line of thought. The first, unsuccessful response is that it is self-defeating to ask why we ought to think. The second response is that we need to think. But this response secures normativity only if thinking has some connection to human flourishing. (4) I argue that thinking is necessary for human flourishing. Logic is normative because it is constitutive of this good. (5) I show that the resulting account deals nicely with problems that vex other accounts of logical normativity. (shrink)

It is commonly thought that logic, whatever it may be, is normative. While accounting for the normativity of logic is a challenge for any view of logic, in this paper I argue that it is particularly problematic for certain types of logical pluralists, due to what I call the normative problem for logical pluralism. I introduce the NPLP, distinguish it from other problems that logical pluralists may face, and show that it is unsolvable for one prominent type of logical pluralism.

Logical pluralism is the view that there is more than one logic. Logical normativism is the view that logic is normative. These positions have often been assumed to go hand-in-hand, but we show that one can be a logical pluralist without being a logical normativist. We begin by arguing directly against logical normativism. Then we reformulate one popular version of pluralism—due to Beall and Restall—to avoid a normativist commitment. We give three non-normativist pluralist views, the most promising of which depends (...) not on logic’s normativity but on epistemic goals. (shrink)

Many people hold that there is a distinctive notion of metaphysical necessity. In this paper I explain why I am skeptical about the view. I examine the sorts of considerations that are adduced for it, and argue that they meet equal and opposite considerations.

What is the relationship between logic and thought? One view is that logic merely describes how people think. But this view – called 'psychologism' – cannot be quite right. Logic cannot describe how people reason, because although people can reason well, they can also reason badly. The obvious response is to say that logic does not describe how people do think, but rather prescribes how they ought to think. If logic describes how people ought to reason, then if the premises (...) of a logical argument imply the conclusion of that argument and you believe the premises, then you ought to believe the conclusion. According to classical logic the premise, 'grass is green' implies the conclusion, 'the sky is blue or the sky is not blue', but it seems absurd to say that because I believe that grass is green, I ought to believe that the sky is blue or the sky is not blue. What has gone wrong here? Should the principle, 'if the premises imply the conclusion and you believe the premises, then you ought to believe the conclusion' be changed? If so, perhaps it would be more correct to say, 'if the premises imply the conclusion and you believe the premises, then you have reason to believe the conclusion'. Or is classical logic to blame? Are we mistaken in thinking that 'grass is green' implies 'the sky is blue or the sky is not blue'? I examine a number of arguments that relate to this question. I argue that classical logic deserves a philosophy of logic that does not imply that classical logic is not proper logic. (shrink)

Priest holds anti-exceptionalism about logic. That is, he holds that logic, as a theory, does not have any exceptional status in relation to the theories of empirical sciences. Crucial to Priest’s anti-exceptionalism is the existence of ‘data’ that can force the revision of logical theory. He claims that classical logic is inadequate to the available data and, thus, needs to be revised. But what kind of data can overturn classical logic? Priest claims that the data is our intuitions about the (...) validity of inferences. In order to make sense of this claim, I will appeal to the Madhyamaka Buddhist philosopher Candrakīrti. I will then pose a problem for Priest’s anti-exceptionalism. Finally, I will suggest a way out of the problem for Priest. Whether or not he accepts my solution, I will let him decide. (shrink)

Some writers object to logical pluralism on the grounds that logic is normative. The rough idea is that the relation of logical consequence has consequences for what we ought to think and h...

Priest and others have presented their “most telling” argument for paraconsistent logic: that only paraconsistent logics allow non-trivial inconsistent theories. This is a very prevalent argument; occurring as it does in the work of many relevant and more generally paraconsistent logicians. However this argument can be shown to be unsuccessful. There is a crucial ambiguity in the notion of non-triviality. Disambiguated the most telling reason for paraconsistent logics is either question-begging or mistaken. This highlights an important confusion about the role (...) of logic in our development of our theories of the world. Does logic chart good reasoning or our commitments? We also consider another abductive argument for paraconsistent logics which also is shown to fail. (shrink)

Logical consequence is a notion that every person who reasons must possess, at least implicitly. To give a precise and accurate characterization of this notion is the fundamental task of logic. In a similar way, the notion of effectivity is a concept that anyone with a basic training in mathematics possesses, and the most fundamental task of a theory of computability is to give a precise characterization of this notion. The problem concerning effectivity was solved in the 1930s, almost as (...) soon as it was raised, by the work of Turing, Church, and others. By contrast, the correct and precise characterization of logical consequence has been hotly contested through the two and a half thousand-year history of logic. (shrink)

Many philosophers claim that understanding a logical constant (e.g. ‘if, then’) fundamentally consists in having dispositions to infer according to the logical rules (e.g. Modus Ponens) that fix its meaning. This paper argues that such dispositionalist accounts give us the wrong picture of what understanding a logical constant consists in. The objection here is that they give an account of understanding a logical constant which is inconsistent with what seem to be adequate manifestations of such understanding. I then outline an (...) alternative account according to which understanding a logical constant is not to be understood dispositionally, but propositionally. I argue that this account is not inconsistent with intuitively correct manifestations of understanding the logical constants. (shrink)

This paper argues that the prominent accounts of logical knowledge have the consequence that they conflict with ordinary reasoning. On these accounts knowing a logical principle, for instance, is having a disposition to infer according to it. These accounts in particular conflict with so-called ‘reasoned change in view’, where someone does not infer according to a logical principle but revise their views instead. The paper also outlines a propositional account of logical knowledge which does not conflict with ordinary reasoning.

Lewisian Genuine Realism about possible worlds is often deemed unable to accommodate impossible worlds and reap the benefits that these bestow to rival theories. This thesis explores two alternative extensions of GR into the terrain of impossible worlds. It is divided in six chapters. Chapter I outlines Lewis’ theory, the motivations for impossible worlds, and the central problem that such worlds present for GR: How can GR even understand the notion of an impossible world, given Lewis’ reductive theoretical framework? Since (...) the desideratum is to incorporate impossible worlds into GR without compromising Lewis’ reductive analysis of modality, Chapter II defends that analysis against objections. The rest of the thesis is devoted to incorporating impossible worlds into GR. Chapter III explores GR-friendly impossible worlds in the form of set-theoretic constructions out of genuine possibilia. Then, Chapters IV-VI venture into concrete impossible worlds. Chapter IV addresses Lewis’ objection against such worlds, to the effect that contradictions true at impossible worlds amount to true contradictions tout court. I argue that even if so, the relevant contradictions are only ever about the non-actual, and that Lewis’ argument relies on a premise that cannot be nonquestion- beggingly upheld in the face of genuine impossible worlds in any case. Chapter V proposes that Lewis’ reductive analysis can be preserved, even in the face of genuine impossibilia, if we differentiate the impossible from the possible by means of accessibility relations, understood non-modally in terms of similarity. Finally, Chapter VI counters objections to the effect that there are certain impossibilities, formulated in Lewis’ theoretical language, which genuine impossibilia should, but cannot, represent. I conclude that Genuine Realism is still very much in the running when the discussion turns to impossible worlds. (shrink)

John Cook Wilson (1849–1915) was Wykeham Professor of Logic at New College, Oxford and the founder of ‘Oxford Realism’, a philosophical movement that flourished at Oxford during the first decades of the 20th century. Although trained as a classicist and a mathematician, his most important contribution was to the theory of knowledge, where he argued that knowledge is factive and not definable in terms of belief, and he criticized ‘hybrid’ and ‘externalist’ accounts. He also argued for direct realism in perception, (...) criticizing both empiricism and idealism, and argued for a moderate nominalist view of universals as being in rebus and only ‘apprehended’ by their particulars. His influence helped swaying Oxford away from idealism and, through figures such as H. A. Prichard, Gilbert Ryle, or J. L. Austin, his ideas were also to some extent at the origin of ‘moral intuitionism’ and ‘ordinary language philosophy’ which defined much of Oxford philosophy until the second half of the twentieth-century. Nevertheless, his name and legacy were all but forgotten for generations after World War II. Still, his views on knowledge are with us today, being in part at work in the writings of philosophers as diverse as John McDowell, Charles Travis, and Timothy Williamson. (shrink)

Twenty-five years ago the ethical position briefly sketched inToward Reunion in Philosophy seemed novel and exciting. For some reason White's ideas about ethics were not taken up and developed by others. (Even a recent extension of Quine's system to ethics seems either to ignore or to be unaware of White's early suggestions. This task was left for White himself over two decades later. Whether his latest development of his ethical position will become as widely discussed and influential as Quine's epistemological (...) view on which it is based is uncertain. But until many of the problems raised above are answered “corporatism” is not perhaps a metaethical position that deserves to become popular. The promise ofToward Reunion of a viable Quinean metaethics has not been fulfilled. (shrink)

Is logic normative for belief? A standard approach to answering this question has been to investigate bridge principles relating claims of logical consequence to norms for belief. Although the question is naturally an epistemic one, bridge principles have typically been investigated in isolation from epistemic debates over the correct norms for belief. In this paper we tackle the question of whether logic is normative for belief by proposing a Kripkean model theory accounting for the interaction between logical, doxastic, epistemic and (...) deontic notions and using this model theory to show which bridge principles are implied by epistemic norms that we have independent reason to accept, for example, the knowledge norm and the truth norm. We propose a preliminary theory of the interaction between logical, doxastic, epistemic and deontic notions that has among its commitments bridge principles expressing how logic is normative for belief. We also show how our framework suggests that logic is exceptionally normative. (shrink)

According to ordinary language philosophy (OLP), philosophical problems can be solved by investigating ordinary language, often because the problems stem from its misuse. According to ideal language philosophy (ILP), on the other hand, philosophical problems exist because ordinary language is flawed and has to be improved or replaced by constructed languages that do not exhibit these flaws. OLP and ILP together make up linguistic philosophy, the view that philosophical problems are problems of language. Linguistic philosophy is opposed to what may (...) be called, for lack of a better word, ‘traditional philosophy’ (TP), the view that philosophical problems can be solved by discovering non-linguistic facts. In the following, OLP, ILP, and TP are taken to be methodologies, that is, frameworks in which to interpret and evaluate different philosophical methods (i.e., argumentative strategies). The two linguistic methodologies are discussed separately with TP as a foil, and then used to interpret the status of different philosophical methods. While each of the methods discussed here finds a plausible interpretation in each methodology, there are other arguments for and against linguistic philosophy in general, and for and against ILP and OLP in particular. As none of these arguments is decisive, I conclude with a superficial moral about peaceful co-existence. (shrink)

Western contemporary logic has been used to advance the field of Islamic philosophical theology, which historically utilised Aristotelian-Avicennian logic, on grounds of there being an inherent normativity in logic. This is in spite of the surrounding controversy on the status of logic in the Islamic theological tradition. The normative authority of logic means that it influences the content of what we ought to believe and how we ought to revise those beliefs. This paper seeks to demonstrate that, notwithstanding the incompatible (...) differences between the two systems, the underlying feature of both Western contemporary logic and Aristotelian- Avicennian logic is logical normativity. It then argues that an inherent normativity of logic in the Islamic theological/philosophical tradition is unmotivated. Instead, it proposes to reinstate logic as anti-exceptional within the Islamic theological/philosophical tradition as a viable alternative. (shrink)

There was a time when 'logic' just meant classical logic. The climate is slowly changing and non-classical logic cannot be dismissed off-hand. However, a metatheory used to study the properties of non-classical logic is often classical. In this paper, we will argue that this practice of relying on classical metatheories is problematic. In particular, we will show that it is a bad practice because the metatheory that is used to study a non-classical logic often rules out the very logic it (...) is designed to study. (shrink)

Logicians disagree about how validity—the very heart of logic—should be understood. Many different formal systems have been born due to this disagreement. This thesis examines how teachers explain the subject matter of logic to students in introductory logic textbooks, and demonstrates the different explanations teachers use. These differences help explain why logicians have different intuitions about validity.

Logic has traditionally been construed as a normative discipline; it sets forth standards of correct reasoning. Explosion is a valid principle of classical logic. It states that an inconsistent set of propositions entails any proposition whatsoever. However, ordinary agents presumably do — occasionally, at least — have inconsistent belief sets. Yet it is false that such agents may, let alone ought to, believe any proposition they please. Therefore, our logic should not recognize explosion as a logical law. Call this the (...) ‘normative argument against explosion’. Arguments of this type play — implicitly or explicitly — a central role in motivating paraconsistent logics. Branden Fitelson, in a throwaway remark, has conjectured that there is no plausible ‘bridge principle’ articulating the normative link between logic and reasoning capable of supporting such arguments. This paper offers a critical evaluation of Fitelson’s conjecture, and hence of normative arguments for paraconsistency and the conceptions of logic’s normative status on which they repose. It is argued that Fitelson’s conjecture turns out to be correct: normative arguments for paraconsistency probably fail. (shrink)

This book contains a selection of the papers presented at the Logic, Reasoning and Rationality 2010 conference in Ghent. The conference aimed at stimulating the use of formal frameworks to explicate concrete cases of human reasoning, and conversely, to challenge scholars in formal studies by presenting them with interesting new cases of actual reasoning. According to the members of the Wiener Kreis, there was a strong connection between logic, reasoning, and rationality and that human reasoning is rational in so far (...) as it is based on logic. Later, this belief came under attack and logic was deemed inadequate to explicate actual cases of human reasoning. Today, there is a growing interest in reconnecting logic, reasoning and rationality. A central motor for this change was the development of non-classical logics and non-classical formal frameworks. The book contains contributions in various non-classical formal frameworks, case studies that enhance our apprehension of concrete reasoning patterns, and studies of the philosophical implications for our understanding of the notions of rationality. (shrink)

I argue that Quine’s early critique of Carnap’s conventionalism is in serious tension with the holism of "Two Dogmas of Empiricism", since his critique of convention- alism makes a compelling case for a privileged status either for logic, or for some other principle by means of which to derive consequences. Based on this, I call for a modification of Quinean holism, on grounds internal to Quine’s views. The result motivates a rehabilitation of Carnap’s notion of framework principles, and a rethinking (...) of logic as a kind of relativised a priori. (shrink)

This paper sharpens the distinction between inferential and logcon arguments. Inferential arguments represent possible inferences, logcon ones need not. This distinction clarifies the roles that arguments play in accounting for the normativity of validity for inferential reasoning and in establishing the theoretical connection between validity and logical consequence. There are two related takeaways. First, the normativity of validity for inferential reasoning is grounded on the notion of an inferential argument. This will account for the use of validity to judge inference (...) in the face of well-known skepticism that a theory of validity has any special relevance to inferential reasoning. Second, a valid logcon argument needn't be an inferential argument. Accordingly, the normativity of validity for inferential reasoning doesn't require that every valid logcon argument be an inferential argument. The takeaways harmonize the use of validity to evaluate inferential reasoning with the use of the concept of logical consequence to characterize validity. (shrink)

In this paper, Graham Priest’s understanding of dialetheism, the view that there exist true contradictions, is discussed, and various kinds of metaphysical dialetheism are distinguished between. An alternative to dialetheism is presented, namely a thesis called ‘dimathematism’. It is pointed out that dimathematism enables one to escape a slippery slope argument for dialetheism that has been put forward by Priest. Moreover, dimathematism is presented as a thesis that is helpful in rejecting the claim that logic is a normative discipline.

Zapadna suvremena logika korištena je za unapređenje islamske filozofske teologije, koja je povijesno koristila aristotelovsko-avicenovsku logiku, na temelju toga što se logika shvaćala kao inherentno normativna. To je usprkos kontroverzama o statusu logike u islamskoj teološkoj tradiciji. Normativni autoritet logike znači da ona utječe na sadržaj onoga u što bismo trebali vjerovati i na to kako bismo trebali revidirati ta uvjerenja. Ovaj rad nastoji pokazati da je, bez obzira na nekompatibilne razlike između dvaju sustava, temeljna značajka zapadne suvremene logike i (...) aristotelovsko-avicenovske logike njihova normativnost. Zatim se tvrdi da je inherentna normativnost logike u islamskoj teološkoj/filozofskoj tradiciji nemotivirana. Umjesto toga, kao održivu alternativu rad predlaže ponovno uspostavljanje logike kao anti-ekscepcionalističke unutar islamske teološke/filozofske tradicije. (shrink)

The paper gives a semantics for naive (inconsistent) set theory in terms of substitutional quantification. Soundness is proved in an appendix. In the light of this construction, Several philosophical issues are discussed, Including mathematical necessity and the set theoretic paradoxes. Most importantly, It is argued, These semantics allow for a nominalist account of mathematical truth not committed to the existence of a domain of abstract entities.

The last half of this century witnessed a proliferation of competing and complimentary theories of argumentation, initiated by the methodological shift from the "product" to the "process" of argument. This paper considers the effect of that shift by c omparing the different logical and epistemic status various theories assign to the standards of argument analysis and evaluation. In view of such differences, I argue that the systematic study of argumentation must clearly demarcate the normative and emp irical study of argumentation (...) with sensitivity to both the limit and significance of each. (shrink)

Olav Gjelsvik: Quine on Observationality: This chapter discusses the role of the observationality of objects in Quine's philosophy. It does it by providing an overview of some of the milestones in Quine's thoughts about observation and observation sentences, and in connection with each milestone it identifies some of the philosophical problems Quine responds to and deals with. To help us understand how his thinking developed, the chapter discusses some of these problems and evaluates his responses. The final part discusses both (...) details and the bigger picture, partly by relating Quine to philosophers before him and after him. (shrink)