The paper asks under what conditions deductive reasoning transmits justification from its premises to its conclusion. It argues that both standard externalist and standard internalist accounts of this phenomenon fail. The nature of this failure is taken to indicate the way forward: basic forms of deductive reasoning must justify by being instances of 'blind but blameless' reasoning. Finally, the paper explores the suggestion that an inferentialist account of the logical constants can help explain how such reasoning is possible.

This revised and considerably expanded 2nd edition brings together a wide range of topics, including modal, tense, conditional, intuitionist, many-valued, paraconsistent, relevant, and fuzzy logics. Part 1, on propositional logic, is the old Introduction, but contains much new material. Part 2 is entirely new, and covers quantification and identity for all the logics in Part 1. The material is unified by the underlying theme of world semantics. All of the topics are explained clearly using devices such as tableau proofs, and (...) their relation to current philosophical issues and debates are discussed. Students with a basic understanding of classical logic will find this book an invaluable introduction to an area that has become of central importance in both logic and philosophy. It will also interest people working in mathematics and computer science who wish to know about the area. (shrink)

Many epistemologists are enamored with a defeat condition on knowledge. In this paper we present some implementation problems for defeatism, understood along either internalist or externalist lines. We then propose that one who accepts a knowledge norm of belief, according to which one ought to believe only what one knows, can explain away much of the motivation for defeatism. This is an important result, because on the one hand it respects the plausibility of the intuitions about defeat shared by many (...) in epistemology; but on the other hand, it obviates the need to provide a unified account of defeat which plays well with the most plausible views of how knowledge fits with evidential probability. (shrink)

One attractive feature of process reliabilism is its reductive potential: it promises to explain justification in entirely non-epistemic terms. In this paper, I argue that the phenomenon of epistemic defeat poses a serious challenge for process reliabilism’s reductive ambitions. The standard process reliabilist analysis of defeat is the ‘Alternative Reliable Process Account’ (ARP). According to ARP, whether S’s belief is defeated depends on whether S has certain reliable processes available to her which, if they had been used, would have resulted (...) in S not holding the belief in question. Unfortunately, ARP proves untenable. I show, by way of counterexample, that ARP fails to articulate either necessary or sufficient conditions on defeat. Process reliabilists must either provide an alternative reductive account of defeat or renounce their reductive aspirations. (shrink)

This is a survey article about epistemic defeaters: what is defeated, how defeaters work, different kinds of defeaters, indefeasibility and how defeaters fit into epistemic internalism and externalism.

It is common orthodoxy among internalists and externalists alike that knowledge is lost or defeated in situations involving misleading evidence of a suitable kind. But making sense of defeat has seemed to present a particular challenge for those who reject an internalist justification condition on knowledge. My main aim here is to argue that externalists ought to take seriously a view on which knowledge can be retained even in the face of strong seemingly defeating evidence. As an instructive example, I (...) first discuss whether a theory on which knowledge is belief that is safe from error has the resources for accommodating defeat. I argue that beliefs retained in defeat cases need not be unsafe or true in some accidental way. I then discuss externalist strategies for explaining why we have incorrect intuitions about defeat. The notion of an epistemically reasonable subject plays a central role in my theory. Reasonable subjects adopt general strategies that are good for acquiring true belief and knowledge across a wide range of normal cases, but stubbornly retaining belief in the face of new evidence does not reflect such policies. I argue that though the methods employed by subjects who fail to adjust their beliefs in defeat cases may be perfectly good, they are not good methods to adopt, as their adoption is accompanied by bad dispositions. What emerges is a view on which a subject can know despite being unreasonable, and despite failing to manifest dispositions to know across normal cases. Unreasonable subjects are genuinely criticisable, but like almost anything, knowledge can sometimes be achieved in the absence of a good general strategy. (shrink)

Look before you leap. - Proverb. He who hesitates is lost. - Another proverb.

The aim of this paper is to sketch a theory of justified belief. What I have in mind is an explanatory theory, one that explains in a general way why certain beliefs are counted as justified and others as unjustified. Unlike some traditional approaches, I do not try to prescribe standards for justification that differ from, or improve upon, our ordinary standards. I merely try to explicate the ordinary standards, which are, I believe, quite different from those of many classical, (...) e. g., ‘Cartesian’, accounts. (shrink)

Can known disagreement with our epistemic peers undermine or defeat the justification our beliefs enjoy? Much of the current literature argues for one of two extreme positions on this topic, either that the justification of each person's belief is (fully) defeated by the awareness of disagreement, or that no belief is defeated by this awareness. I steer a middle course and defend a principle describing when a disagreement yields a partial defeater, which results in a loss of some, but not (...) all, of the justification of a belief. I show that the 'no defeater' view is too strong. I also offer reasons for thinking that the 'full defeater' view is similarly mistaken. (shrink)

Testimony is an invaluable source of knowledge. We rely on the reports of those around us for everything from the ingredients in our food and medicine to the identity of our family members. Recent years have seen an explosion of interest in the epistemology of testimony. Despite the multitude of views offered, a single thesis is nearly universally accepted: testimonial knowledge is acquired through the process of transmission from speaker to hearer. In this book, Jennifer Lackey shows that this thesis (...) is false and, hence, that the literature on testimony has been shaped at its core by a view that is fundamentally misguided. She then defends a detailed alternative to this conception of testimony: whereas the views currently dominant focus on the epistemic status of what speakers believe, Lackey advances a theory that instead centers on what speakers say. The upshot is that, strictly speaking, we do not learn from one another's beliefs - we learn from one another's words. Once this shift in focus is in place, Lackey goes on to argue that, though positive reasons are necessary for testimonial knowledge, testimony itself is an irreducible epistemic source. This leads to the development of a theory that gives proper credence to testimony's epistemologically dual nature: both the speaker and the hearer must make a positive epistemic contribution to testimonial knowledge. The resulting view not only reveals that testimony has the capacity to generate knowledge, but it also gives appropriate weight to our nature as both socially indebted and individually rational creatures. The approach found in this book will, then, represent a radical departure from the views currently dominating the epistemology of testimony, and thus is intended to reshape our understanding of the deep and ubiquitous reliance we have on the testimony of those around us. (shrink)

Virtually all philosophers agree that for a belief to be epistemically justified, it must satisfy certain conditions. Perhaps it must be supported by evidence. Or perhaps it must be reliably formed. Or perhaps there are some other "good-making" features it must have. But does a belief's justification also require some sort of awareness of its good-making features? The answer to this question has been hotly contested in contemporary epistemology, creating a deep divide among its practitioners. Internalists, who tend to focus (...) on scientific or theoretical beliefs as the ideal, insist that such awareness is required for justification. Externalists, who think children's ordinary beliefs in obvious facts are paradigm cases of justified belief, say it isn't required. Michael Bergmann's book offers a decisive refutation of internalism and a sustained defense of externalism. (shrink)

Something about this argument sounds funny. As we’ll see, though, it takes some care to identify exactly what Moore has done wrong. Iwill assume that Moore knows premise (2) to be true. One could inquire into how he knows it, and whether that knowledge can be defeated; but Iwon’t. I’ll focus instead on what epistemic relations Moore has to premise (1) and to his conclusion (3). It may matter which epistemic relations we choose to consider. Some philosophers will diagnose Moore’s (...) argument using Contextualist machinery. They’ll say. (shrink)

Those of us who take skepticism seriously typically have two relevant beliefs: (a) it’s plausible (even if false) that in order to know that I have hands I have to be able to epistemically neutralize, to some significant degree, some skeptical hypotheses, such as the brain-in-a-vat (BIV) one; and (b) it’s also plausible (even if false) that I can’t so neutralize those hypotheses. There is no reason for us to also think (c) that the BIV hypothesis, for instance, is plausible (...) or probably true. In order to take skepticism seriously it’s sufficient to hold (a) and (b); one need not hold (c). Indeed, philosophers who accept (a) and (b) never endorse (c). Show me a philosopher who suspects that he is a brain in a vat and I’ll show you someone who is deranged! That’s one thing that bothers undergraduates in philosophy. They object: why on earth do some philosophers take the BIV hypothesis to pose any threat at all to our beliefs given that those very same philosophers think that there’s no real chance that the BIV hypothesis is true? Sure, the BIV hypothesis is formally inconsistent with my belief that I have hands, so if the former is true then my belief is false. But so what? Why should that bare inconsistency matter so much? Is this strange attitude amongst philosophers the result of some logic fetish infecting the philosophical community? It is sometimes said that the skeptical hypotheses are not only inconsistent with our beliefs but are explanatory of our experiences, which is supposed to make them more of a threat. But students aren’t fooled: although the skeptical hypotheses may attempt to explain why our experience is as it is, it’s the kind of attempt appropriate for science fiction movies that are all special effects and virtually no plot. No one with any sense of reality will take the evil demon hypothesis to be even tenuously explanatory. (shrink)

Internalists tend to impose on justification higher-level requirements, according to which a belief is justified only if the subject has a higher-level belief (i.e., a belief about the epistemic credentials of a belief). I offer an error theory that explains the appeal of this requirement: analytically, a belief is not justified if we have a defeater for it, but contingently, it is often the case that to avoid having defeaters, our beliefs must satisfy a higher-level requirement. I respond to the (...) objection that externalists who endorse this error theory will be forced to accept a radical form of scepticism. (shrink)

Some time ago, F. P. Ramsey (1960) suggested that knowledge is true belief obtained by a reliable process. This suggestion has only recently begun to attract serious attention. In 'Discrimination and Perceptual Knowledge', Alvin Goldman (1976) argues that a person has knowl- edge only if that person's belief has been formed as a result of a reliable cognitive mechanism. In Belief, Truth, and Knowledge, David Arm- strong (1973) argues that one has knowledge only if one's belief is a comPletely reliable (...) sign of the truth of the proposition believed. On both of these theories, the reliability of one's belief is a necessary condition of that belief's being an instance of knowledge. These reliability theories have another interesting feature in common, namely, that neither of them explicitly requires or includes the traditional justification requirement for knowledge. Reliability has taken over the role of justification. This naturally leads to the question whether reliability and justification are related in some philosophically interes- ting fashion. In this paper I shall investigate this question. The result will be a positive proposal to the effect that justified belief is reliable belief. This result, in turn, explains why reliability can take over the role of justification in an account of knowledge. Moreover, the identification of justification with reliability constitutes a step toward the naturalization of normative epistemological concepts. (shrink)

Princeton University Press, 1974. This book is out of print, but can be downloaded as a pdf file (5 MB).

The epistemic basing relation is the relation occurring between a belief and a reason when the reason is the reason for which the belief is held. It marks the distinction between a belief's being justifiable for a person, and the person's being justified in holding the belief. As such, it is an essential component of any complete theory of epistemic justification. ;I survey and evaluate all theories of the basing relation that I am aware of published between 1965 and 1995. (...) These include causal theories, , theories involving pseudo-overdetermination relations , theories involving what a person would appeal to in defense of her beliefs , and doxastic theories , involving an appeal to meta-beliefs. My discussion of these theories includes a detailed analysis of variations of Lehrer's case of the gypsy lawyer which, I show, can be reformulated to pose a decisive objection to causal theories, if not causal analyses, of the basing relation. ;Rejecting all published theories, I present a new kind of causal analysis of the basing relation which I call the causal-doxastic theory. This theory states that a belief is based on a reason if the reason bears an appropriate causal relation to the belief, or, it does not bear such a causal relation, but an appropriate meta-belief is present. A causal analysis of which meta-beliefs are appropriate is given, so as to count as inappropriate rationalizations, mistaken meta-beliefs, etc. In developing the causal-doxastic theory, I present a solution to the problem of deviant causal chains, a discussion of the causal sustaining of beliefs, an account of rejecting reasons, and a partial analysis of showing that one is justified. I then discuss implications of my theory regarding foundationalism, inference, basic and non-basic belief, holistic and linear coherentism, process reliabilism, internalism and externalism, and various closure principles. (shrink)

It is widely assumed that justification is defeasible, e.g. that under certain conditions counterevidence removes prior justification of beliefs. In this paper I will first (sect. 1) explain why this feature of justification poses a prima facie problem for reliabilism. I then will try out different reliabilist strategies to deal with the problem. Among them I will discuss conservative strategies (sect. 2), eliminativist stragies (sect. 3) and revisionist strategies (sect. 4). In the final section I will present an improved revisionist (...) approach to defeaters that is able to overcome the main shortcomings of the other approaches. (shrink)

This paper proposes a new externalist account of defeaters, in terms of reliable indicators, as an integral part of a unified externalist account of warrant and defeat. It is argued that posing externalist conditions on warrant, but internalist conditions on defeat lead to undesirable tensions. The proposal is contrasted to some rival accounts and then tested on some widely discussed cases, like the airport case. Misleading defeaters, where Laurence BonJour’s reliable clairvoyants serve as examples, also receive treatment, partly because they (...) illustrate how internalist constraints are inserted into the set up of the problem and therefore unduly constrain the domain of satisfactory solutions. Lastly, the proposal is defended against some objections. Firstly, that by posing externalist conditions on defeat, the account becomes too open. Secondly, that an externalist account fails to take into account the epistemic assessments of our fellows in the epistemic practice of forming beliefs and making epistemic claims, which can be based on accessible warrant only. (shrink)

Taking the inspiration from some points made by Scott Sturgeon and Albert Casullo, I articulate a view according to which an important difference between undermining and overriding defeaters is that the former require the subject to engage in some higher-order epistemic thinking, while the latter don’t. With the help of some examples, I argue that underminers push the cognizer to reflect on the way she formed a belief by challenging the epistemic worthiness of either the source of justification or the (...) specific justificatory process. By contrast, overriders needn’t pose any such challenge. I also consider some problems for the proposed view, and I put forward some possible solutions. Finally, I provide some details on how undermining defeat works in different cases. (shrink)