This paper compares two kinds of epistemic principles---an underdetermination principle and a deductive closure principle. It argues that each principle provides the basis for an independently motivated skeptical argument. It examines the logical relations between the premises of the two kinds of skeptical argument and concludes that the deductive closure argument cannot be refuted without refuting the underdetermination argument. The underdetermination argument, however, can be refuted without refuting the deductive closure argument. In this respect, the deductive closure argument is the (...) stronger of the two. (shrink)

A review of Albert Casullo's "A Priori Justification" (Oxford University Press).

In this paper, I will clarify Jonathan Schaffer's; debasing scepticism, highlighting its logical structure. 1 In many current discussions of scepticism, its scope is limited to propositions about the external world which, if known at all, are known a posteriori. The standard sceptical set-up goes as follows. The sceptic specifies a sceptical hypothesis, or counterpossibility, that is incompatible with the external-world propositions that I claim to know. The hypothesis – e.g. that I am a brain in a vat – is (...) claimed by the sceptic to be within the realm of metaphysical possibility. The sceptical argument, in a nutshell, runs as follows. Choose some external-world proposition that I claim to know, say H = I have hands. By the principle that knowledge is closed under known entailment, if I know H, then I know ∼SK = I am not a handless brain in a vat. My evidence does not enable me to know ∼SK. Hence I …. (shrink)

Die philosophische Skepsis bezweifelt argumentativ, dass Menschen über Wissen verfügen. Eine interessante und viel beachtete Reaktion auf diese Skepsis basiert auf dem semantischen Externalismus. Obwohl die antiskeptische Strategie des Externalismus im Laufe der Jahre entscheident verbessert wurde, krankt sie in den Augen vieler Philosophen immer noch an einer stark beschränkten Reichweite: Sie ist nur hinsichtlich ganz bestimmter Varianten skeptischer Argumentation erfolgreich – durch geschickte Modifikation des skeptischen Arguments ist der Skeptiker in der Lage, sein Argument gegen den externalistischen Angriff zu (...) immunisieren. In diesem Artikel gehe ich der Frage nach, ob die vom Externalismus erzwungene modifizierte Fassung des skeptischen Arguments anfälliger für antiskeptische Angriffe ist als die ursprüngliche Version. Drei Versuche, die vom Externalismus erzwungene Modifikation des skeptischen Arguments in antiskeptischer Hinsicht auszunutzen, werden diskutiert. Einer der Versuche erscheint zunächst viel versprechend, doch letztlich erweisen sich alle drei antiskeptischen Folgestrategien als unbefriedigend. (shrink)

I examine the conditions which hypotheses must satisfy if they are to be used to raise significant sceptical challenges. I argue that sceptical hypotheses do not have to be logically, metaphysically or epistemically possible: they need only to depict scenarios subjectively indistinguishable from the actual world and to show how subjects can believe what they do while not having knowledge. I also argue that sceptical challenges can be raised against a priori beliefs, even if those beliefs are necessarily true. I (...) hope to broaden our conception of the legitimate kinds of sceptical challenges which can be raised. (shrink)

In this article I investigate a neglected form of radical skepticism that questions whether any of our logical, mathematical and other seemingly self-evident beliefs count as knowledge. ‘A priori skepticism,’ as I will call it, challenges our ability to know any of the following sorts of propositions: (1.1) The sum of two and three is five. (1.2) Whatever is square is rectangular. (1.3) Whatever is red is colored. (1.4) No surface can be uniformly red and uniformly blue at the same (...) time. (1.5) If ‘if p then q’ is true and ‘p’ is true, then ‘q’ is true. (1.6) No statement can be both true and false at the same time and in the same respect. (1.7) If A is taller than B, and B is taller than C, then A is taller than C. (1.8) Everything is identical to itself. (1.9) If the conclusion of an inductive argument is contingent, it is possible for the premises of that argument to be true and its conclusion to be false. (1.10) George W. Bush could have been a plumber. (1.11) George W. Bush could not have been a prime number. (1.12) ‘2 + 3 = 5’ is necessarily true. (shrink)

This article is a response to an important objection that Sherrilyn Roush has made to the standard closure-based argument for skepticism, an argument that has been studied over the past couple of decades. If Roush's objection is on the mark, then this would be a quite significant finding. We argue that her objection fails.

David Lewis (1941-2001) was Class of 1943 University Professor of Philosophy at Princeton University. His contributions spanned philosophical logic, philosophy of language, philosophy of mind, philosophy of science, metaphysics, and epistemology. In On the Plurality of Worlds, he defended his challenging metaphysical position, "modal realism." He was also the author of the books Convention, Counterfactuals, Parts of Classes, and several volumes of collected papers.

Contemporary discussions of skepticism often frame the skeptic's argument around an instance of the closure principle. Roughly, the closure principle states that if a subject knows p, and knows that p entails q, then the subject knows q. The main contention of this paper is that the closure argument for skepticism is defective. We explore several possible classifications of the defect. The closure argument might plausibly be classified as begging the question, as exhibiting transmission failure, or as structurally inefficient. Interestingly, (...) perhaps, each of these has been proposed as the correct classification of Moore's proof of an external world. (shrink)

Reliabilist accounts of knowledge are widely seen as having the resources for blocking sceptical arguments, since these arguments appear to rely on assumptions about the nature of knowledge that are rendered illegitimate by reliabilist accounts. The goal of this book is to assess the main arguments against the possibility of knowledge, and its conclusions challenge this consensus. The book articulates and defends a theory of knowledge that belongs firmly in the truth-tracking tradition, and argues that although the theory has the (...) resources for blocking the main standard lines of sceptical reasoning, there is a sceptical argument against which the theory offers no defence, as it doesn’t rely on any assumptions that the theory would render illegitimate. The book ends with the suggestion that the problem might have a metaphysical solution—that although the sceptical argument may make no illegitimate epistemological assumptions, it does rest on a questionable account of the nature of cognition. (shrink)

Knowledge and its Limits presents a systematic new conception of knowledge as a kind of mental stage sensitive to the knower's environment. It makes a major contribution to the debate between externalist and internalist philosophies of mind, and breaks radically with the epistemological tradition of analyzing knowledge in terms of true belief. The theory casts new light on such philosophical problems as scepticism, evidence, probability and assertion, realism and anti-realism, and the limits of what can be known. The arguments are (...) illustrated by rigorous models based on epistemic logic and probability theory. The result is a new way of doing epistemology and a notable contribution to the philosophy of mind. (shrink)

Philosophical Papers 36.1 (2007): 151-161.

This new edition of the classic Contemporary Theories of Knowledge has been significantly updated to include analyses of the recent literature in epistemology.

: It is generally accepted that skeptical scenarios must be possible to raise legitimate skeptical doubt. I argue that if the possibility in question is supposed to be genuine metaphysical possibility, the skeptic's reasoning does not straightforwardly succeed. I first motivate the metaphysical possibility requirement on skeptical scenarios : it's a plausible position that several authors accept and that a family of prominent views—sensitivity, safety, relevant alternatives—are committed to. I argue that plausible constraints in modal epistemology show that justification for (...) believing that certain global skeptical scenarios are metaphysically possible rests on some justified beliefs about the external world, and that this undermines the skeptical argument. While there may still be local skeptical challenges, skeptics cannot appeal to the metaphysical possibility of skeptical scenarios to generate global external world skepticism. (shrink)

§I schematises the evidence for an understanding of ‘know’ and other terms of epistemic appraisal that embodies contextualism or subject-sensitive invariantism, and distinguishes between those two approaches. §II argues that although the cases for contextualism and sensitive invariantism rely on a principle of charity in the interpretation of epistemic claims, neither approach satisfies charity fully, since both attribute metalinguistic errors to speakers. §III provides an equally charitable anti-sceptical insensitive invariantist explanation of much of the same evidence as the result of (...) psychological bias caused by salience effects. §IV suggests that the explanation appears to have implausible consequences about practical reasoning, but also that applications of contextualism or sensitive invariantism to the problem of scepticism have such consequences. §V argues that the inevitable difference between appropriateness and knowledge of appropriateness in practical reasoning, closely related to the difference between knowledge and knowledge of knowledge, explains the apparent implausibility. (shrink)

It is often said, metaphorically, that belief "aims" at the truth. This paper proposes a normative interpretation of this metaphor. First, the notion of "epistemic norms" is clarified, and reasons are given for the view that epistemic norms articulate essential features of the beliefs that are subject to them. Then it is argued that all epistemic norms--including those that specify when beliefs count as rational, and when they count as knowledge--are explained by a fundamental norm of correct belief, which requires (...) that, if one considers a proposition at all, one should believe it if and only if it is true. (shrink)

What knowledge is imperilled by sceptical doubt? That is, what range of beliefs may be called into doubt by sceptical nightmares like the Cartesian demon hypothesis? It is generally thought that demons have limited powers, perhaps only threatening a posteriori knowledge of the external world, but at any rate not threatening principles like the cogito. I will argue that there is a demon – the debasing demon – with unlimited powers, which threatens universal doubt. Rather than deceiving us with falsities, (...) the debasing demon would allow us true beliefs, but only as guesses. (shrink)

It is received wisdom that the skeptic has a devastating line of argument in the following. You probably think, he says, that you know that you have hands. But if you knew that you had hands, then you would also know that you were not a brain in a vat, a brain suspended in fluid with electrodes feeding you perfectly coordinated impressions that are generated by a supercomputer, of a world that looks and moves just like this one. You would (...) know you weren’t in this state if you knew you had hands, since having hands implies you are no brain in a vat. You obviously don’t know you’re not a brain in a vat, though—you have no evidence that would distinguish that state from the normal one you think you’re in. Therefore, by modus tollens, you don’t know you have hands. At least, the skeptic has a devastating argument, it is thought, if we grant him closure of knowledge under known implication, which many of us are inclined to do: roughly, if you know p, and you know that p implies q, then you know q. (shrink)

The traditional argument for skepticism relies on a comparison between a normal subject and a subject in a skeptical scenario: because there is no relevant difference between them, neither has knowledge. Externalists respond by arguing that there is in fact a relevant difference—the normal subject is properly situated in her environment. I argue, however, that there is another sort of comparison available—one between a normal subject and a subject with a belief that is accidentally true—that makes possible a new argument (...) for skepticism. Unlike the traditional form of skeptical argument, this new argument applies equally well to both internalist and externalist theories of knowledge. (shrink)

Consider the skeptic about the external world. Let’s straightaway concede to such a skeptic that perception gives us no conclusive or certain knowledge about our surroundings. Our perceptual justification for beliefs about our surroundings is always defeasible—there are always possible improvements in our epistemic state which would no longer support those beliefs. Let’s also concede to the skeptic that it’s metaphysically possible for us to have all the experiences we’re now having while all those experiences are false. Some philosophers dispute (...) this, but I do not. The skeptic I want to consider goes beyond these familiar points to the much more radical conclusion that our perceptual experiences can’t give us any knowledge or even justification for believing that our surroundings are one way rather than another. (shrink)

Externalists in epistemology often reject the KK principle – which says that if a person knows that p, then they know that they know that p. This paper argues that one standard argument against the KK principle that many externalists make is fallacious, as it involves illicit substitution into an intensional context. The fallacy is exposed and discussed.

What epistemic defect needs to show up in a skeptical scenario if it is to effectively target some belief? According to the false belief account, the targeted belief must be false in the skeptical scenario. According to the competing ignorance account, the targeted belief must fall short of being knowledge in the skeptical scenario. This paper argues for two claims. The first is that, contrary to what is often assumed, the ignorance account is superior to the false belief account. The (...) second is that the ignorance account ultimately hobbles the skeptic. It does so for two reasons. First, when this account is joined with either a closure-based skeptical argument or a skeptical underdetermination argument, the best the skeptic can do is show that we don’t know that we know. And second, the ignorance account directly implies the maligned KK principle. (shrink)

On a common view of scenario-based sceptical arguments sceptical scenarios are error-possibilities, i.e. their point is to introduce the possibility of having only false beliefs. However, global error is impossible for purely logical/conceptual reasons: Even if one’s beliefs are consistent, the negations of one’s beliefs need not be consistent as well. My paper deals with the question of what the consequences of this result are. Two attempts at repairing scenario-based sceptical arguments within the framework of understanding sceptical scenarios as error-possibilities (...) are found wanting. Instead, what should be given up is the assumption that sceptical scenarios are error-possibilities. What is thought-provoking about the scenario of the brain in a vat is not that none of its empirical beliefs are true, but that all of its empirical beliefs fall short of knowledge at the same time. Hence, sceptical scenarios are not error-possibilities, but ignorance possibilities. If this is so, both the closure argument and the underdetermination argument commit a subtle mistake and should be replaced by slightly different arguments. The principle of excluded ignorance-possibilities turns out to be an epistemological principle that is faithful to scepticism’s tenets without misinterpreting sceptical scenarios as error-possibilities. (shrink)

(No abstract is available for this citation).

Various possibilities, that one is dreaming, that one is being deceived by a deceitful demon, that one is a brain in the vat being stimulated to think one has a body and is in a regular world, have been invoked to show that all one's experience-based beliefs might be false. Descartes in Meditation I advises that in order not to lapse into his careless everyday view of things he, or at least his meditator, should pretend that all his experience-based beliefs, (...) indeed all his …. (shrink)

(No abstract is available for this citation).

Cartesian skepticism about epistemic justification (‘skepticism’) is the view that many of our beliefs about the external world – e.g., my current belief that I have hands – aren’t justified. I examine the two most influential arguments for skepticism – the Closure Argument and the Underdetermination Argument – from an evidentialist perspective. For both arguments it is clear which premise the anti-skeptic must deny. The Closure Argument, I argue, is the better argument in that its key premise is weaker than (...) the Underdetermination Argument’s key premise. However, it’s also likely that the motivation for accepting both key premises is exactly the same. So there may be a sense in which both arguments provide exactly the same motivation for skepticism. Then I argue that if I I’m right about what the motivation for accepting the arguments’ key premises is, then neither argument succeeds in providing a good reason to accept skepticism. I conclude by explaining why I think epistemologists are right to expend a lot of time and effort on refuting these arguments, even if neither argument provides any motivation for skepticism. (shrink)

Epistemological disjunctivism in outline -- Favouring versus discriminating epistemic support -- Radical scepticsim.

In this exciting and original introduction to epistemology, Michael Williams explains and criticizes traditional philosophical theories of the nature, limits, methods, possibility, and value of knowing. All the main contemporary perspectives are explored and questioned, and the author's own theories put forward, making this new book essential reading for anyone, beginner or specialist, concerned with the philosophy of knowledge.

Sven Bernecker presents an analysis of the concept of propositional (or factual) memory, and examines a number of metaphysical and epistemological issues crucial to the understanding of memory. -/- Bernecker argues that memory, unlike knowledge, implies neither belief nor justification. There are instances where memory, though hitting the mark of truth, succeeds in an epistemically defective way. This book shows that, contrary to received wisdom in epistemology, memory not only preserves epistemic features generated by other epistemic sources but also functions (...) as a source of justification and knowledge. According to the causal theory of memory argued for in this book, the dependence of memory states on past representations supports counterfactuals of the form: if the subject hadn't represented a given proposition in the past he wouldn't represent it in the present. The book argues for a version of content externalism whereupon the individuation of memory contents depends on relations the subject bears to his past physical or social environment. Moreover, Bernecker shows that memory doesn't require identity, but only similarity, of past and present attitudes and contents. The notion of content similarity is explicated in terms of the entailment relation. (shrink)

The major divide in contemporary epistemology is between those who embrace and those who reject a priori knowledge. Albert Casullo provides a systematic treatment of the primary epistemological issues associated with the controversy. By freeing the a priori from traditional assumptions about the nature of knowledge and justification, he offers a novel approach to resolving these issues which assigns a prominent role to empirical evidence. He concludes by arguing that traditional approaches to the a priori, which focus primarily on the (...) concepts of necessity and analyticity, are misguided. (shrink)

The relation of scepticism to infallibilism and fallibilism is a contested issue. In this paper I argue that Cartesian sceptical arguments, i.e. sceptical arguments resting on sceptical scenarios, are neither tied to infallibilism nor collapse into fallibilism. I interpret the distinction between scepticism and fallibilism as a scope distinction. According to fallibilism, each belief could be false, but according to scepticism all beliefs could be false at the same time. However, to put this distinction to work sceptical scenarios have to (...) be understood as ignorance-possibilities, not as error-possibilities. To show that scepticism is not tied to infallibilism I reject the principle of unrestricted relevance according to which any error- or ignorance-possibility whatsoever is relevant. Instead I argue that the sceptic should distinguish between local and global ignorance-possibilities. Global ignorance-possibilities are relevant even though not all ignorance-possibilities are relevant. The result is a refined version of the Cartesian sceptical argument that avoids two traps other versions do not avoid. (shrink)