Defeasibility Theory of Knowledge

Is knowledge consistent with literally any credence in the relevant proposition, including credence 0? Of course not. But is credence 0 the only credence in p that entails that you don’t know that p? Knowledge entails belief (most epistemologists think), and it’s impossible to believe that p while having credence 0 in p. Is it true that, for every value of ‘x,’ if it’s impossible to know that p while having credence x in p, this is simply because it’s impossible (...) to believe that p while having credence x in p? If so, is it possible to believe that p while having (say) credence 0.4 in p? These questions aren’t standard epistemological fare, at least in part because many epistemologists think their answers are obvious, but they have unanticipated consequences for epistemology. Let ‘improbabilism’ name the thesis that it’s possible to know that p while having a credence in p below 0.5. Improbabilism will strike many epistemologists as absurd, but careful reflection on these questions reveals that, if improbabilism is false, then all of the most plausible theories of knowledge are also false. Or so I argue in this paper. Since improbabilism is widely rejected by epistemologists (at least implicitly), this paper reveals a tension between all of the most plausible theories of knowledge and a widespread assumption in epistemology. (shrink)

This is a collection of new essays written in honor of the work of Peter D. Klein, who has had and continues to have a tremendous influence in the development of epistemology. The essays reflect the breadth and depth of Klein’s work by engaging directly with his views and with the views of his interlocutors.

Foundationalism in moral epistemology is a core tenet of ethical intuitionism. According to foundationalism, some moral beliefs can be known without inferential justification; instead, all that is required is a proper understanding of the beliefs in question. In an influential criticism against this view, Walter Sinnott-Armstrong has argued that certain psychological facts undermine the reliability of moral intuitions. He claims that foundationalists would have to show that non-inferentially justified beliefs are not subject to those defeaters, but this would already constitute (...) a form of inference and hence undermine the possibility of noninferential justification. The goal of my paper is to defend foundationalism against Sinnott-Armstrong’s criticism. After presenting his challenge, I first argue that the most promising objection to it fails. This objection makes the case that defeater-defeaters are not part of the justification, but merely preserve the justification which the original claim provides. I object to this argument by distinguishing between weak and robust defeaters; only weak defeaters, I argue, fall outside the scope of justification, and it is an open question whether Sinnott-Armstrong’s defeaters fall into that category. This leads the way to my own criticism of Sinnott-Armstrong’s challenge: foundationalists in moral epistemology are entitled to the use of defeater-defeaters as part of the justification for moral beliefs as long as those defeater-defeaters themselves do not entail moral claims. Therefore, Sinnott-Armstrong’s challenge does not undermine foundationalism. (shrink)

Materialism, reductionism, behaviorism, functionalism, dynamic systems theory and computationalism are popular views, but they were shown by Wittgenstein to be incoherent. The study of behavior encompasses all of human life, but behavior is largely automatic and unconscious and even the conscious part, mostly expressed in language (which Wittgenstein equates with the mind), is not perspicuous, so it is critical to have a framework which Searle calls the Logical Structure of Rationality (LSR) and I call the Descriptive Psychology of Higher Order (...) Thought (DPHOT). After summarizing the framework worked out by Wittgenstein and Searle, as extended by modern reasoning research, I show the inadequacies in Carruther’s views, which pervade most discussions of behavior, including contemporary behavioral sciences. I maintain that his book is an amalgam of two books, one a summary of cognitive psychology and the other a summary of the standard philosophical confusions on the mind with some new jargon added. I suggest that the latter should be regarded as incoherent or as a cartoon view of life and that taking Wittgenstein at his word, we can practice successful self therapy by regarding the mind/body issue as a language/body issue. -/- Those wishing a comprehensive up to date framework for human behavior from the modern two systems view may consult my book ‘The Logical Structure of Philosophy, Psychology, Mind and Language in Ludwig Wittgenstein and John Searle’ 2nd ed (2019). Those interested in more of my writings may see ‘Talking Monkeys--Philosophy, Psychology, Science, Religion and Politics on a Doomed Planet--Articles and Reviews 2006-2019 3rd ed (2019), The Logical Structure of Human Behavior (2019), and Suicidal Utopian Delusions in the 21st Century 4th ed (2019) . (shrink)

According to the Reasoning View about normative reasons, facts about normative reasons for action can be understood in terms of facts about the norms of practical reasoning. I argue that this view is subject to an overlooked class of counterexamples, familiar from debates about Subjectivist theories of normative reasons. Strikingly, the standard strategy Subjectivists have used to respond to this problem cannot be adapted to the Reasoning View. I think there is a solution to this problem, however. I argue that (...) the norms of practical reasoning, like the norms of theoretical reasoning, are characteristically defeasible, in a sense I make precise. Recognizing this property of those norms makes space for a solution to the problem. The resulting view is in a way analogous to the familiar defeasibility theory of knowledge, but it avoids a standard objection to that theory. (shrink)

John N. Williams argued that Peter Klein's defeasibility theory of knowledge excludes the possibility of one knowing that one has a posteriori knowledge. He does that by way of adding a new twist to an objection Klein himself answered more than forty years ago. In this paper I argue that Williams' objection misses its target because of this new twist.

I objected that the defeasibility theory of knowledge prohibits you from knowing that you know that p if your knowledge that p is a posteriori. Rodrigo Borges claims that Peter Klein has already satisfactorily answered a version of my objection. He attempts to defend Klein’s reply and argues that my objection fails because a principle on which it is based is false.I will show that my objection is not a version of the old one that Klein attempts (unsuccessfully) to address, (...) that Borges’ defence of Klein’s reply fails and that his argument against my new objection leaves it untouched. (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)

In Epistemic Entitlement. The Right to Believe Hannes Ole Matthiessen develops a social externalist account of epistemic entitlement and perceptual knowledge. The basic idea is that positive epistemic status should be understood as a specific kind of epistemic right, that is a right to believe. Since rights have consequences for how others are required to treat the bearer of the right, they have to be publicly accessible. The author therefore suggests that epistemic entitlement can plausibly be conceptualized as a status (...) that is grounded in a publicly observable perceptual situation, rather than in a perceptual experience as current theories of epistemic entitlement state. It is then argued that such a social externalist account of entitlement, in which the perceiver's epistemic perspective becomes relevant only in the exceptional case where an entitlement is challenged, can nevertheless do justice to our central intuitions about first-personal epistemic phenomenology. (shrink)

Defeasibility, most generally speaking, means that given some set of conditions A, something else B will hold, unless or until defeating conditions C apply. While the term was introduced into philosophy by legal philosopher H.L.A. Hart in 1949, today, the concept of defeasibility is employed in many different areas of philosophy. This volume for the first time brings together contributions on defeasibility from epistemology , legal philosophy and ethics and the philosophy of action . The volume ends with an extensive (...) bibliography. (shrink)

Richard Feldman and William Lycan have defended a view according to which a necessary condition for a doxastic agent to have knowledge is that the agent’s belief is not essentially based on any false assumptions. I call this the no-essential-false-assumption account, or NEFA. Peter Klein considers examples of what he calls “useful false beliefs” and alters his own account of knowledge in a way which can be seen as a refinement of NEFA. This paper shows that NEFA, even given Klein’s (...) refinement, is subject to counterexample: a doxastic agent may possess knowledge despite having an essential false assumption. Advocates of NEFA could simply reject the intuition that the example is a case of knowledge. However, if the example is interpreted as not being a case of knowledge, then it can be used as a potential counterexample against both safety and sensitivity views of knowledge. I also provide a further case which, I claim, is problematic for all of the accounts just mentioned. I then propose, briefly, an alternative account of knowledge which handles all these cases appropriately. (shrink)

When epistemologists talk about knowledge, the discussions traditionally include only a small class of other epistemic notions: belief, justification, probability, truth. In this paper, we propose that epistemologists should include an additional epistemic notion into the mix, namely the notion of assuming or taking for granted.

The paper considers contemporary models of presumption in terms of their ability to contribute to a working theory of presumption for argumentation. Beginning with the Whatelian model, we consider its contemporary developments and alternatives, as proposed by Sidgwick, Kauffeld, Cronkhite, Rescher, Walton, Freeman, Ullmann-Margalit, and Hansen. Based on these accounts, we present a picture of presumptions characterized by their nature, function, foundation and force. On our account, presumption is a modal status that is attached to a claim and has the (...) effect of shifting, in a dialogue, a burden of proof set at a local level. Presumptions can be analysed and evaluated inferentially as components of rule-based structures. Presumptions are defeasible, and the force of a presumption is a function of its normative foundation. This picture seeks to provide a framework to guide the development of specific theories of presumption. (shrink)

Applying a theory of psychological modularity, I argue for a theory of defeasibility conditions for the epistemic justification of perceptual beliefs. My theory avoids the extremes of holism (e.g., coherentism and confirmation holism) and of foundationalist theories of non-inferential justification.

John Hawthorne’s marvelous book contains a wealth of arguments and insights based on an impressive knowledge and understanding of contemporary discussion. We can address only a small aspect of the topic. In particular, we will offer our own answers to two questions about knowledge that he discusses.

In this paper I discuss the relation between various properties that have been regarded as important for determining whether or not a belief constitutes a piece of knowledge: its stability, strength and sensitivity to truth, as well as the strength of the epistemic position in which the subject is with respect to this belief. Attempts to explicate the relevant concepts more formally with the help of systems of spheres of possible worlds (à la Lewis and Grove) must take care to (...) keep apart the very different roles that systems of spheres can play. Nozicks sensitivity account turns out to be closer to the stability analysis of knowledge (versions of which I identify in Plato, Descartes, Klein and Lehrer) than one might have suspected. (shrink)

Philosophers have sought to characterize a type of knowledge — what I call real knowledge — which is significantly different from the ordinary concept of knowledge. The concept of knowledge as true, justified belief — what I call knowledge simpliciter — failed to depict the sought after real knowledge because the necessary and jointly sufficient conditions of knowledge simpliciter can be felicitously but accidentally fulfilled. Real knowledge is knowledge simpliciter plus a set of requirements which guarantee that the truth, belief (...) and justification conditions are not accidentally conjoined. Two of those requirements have received considerable attention in recent literature by the defeasibility theorists and the causal theorists. I argue that a third requirement is needed to block the merely coincidental cosatisfaction of the belief and justification conditions and to capture our intuitions about the epistemic agent who possesses real knowledge. That condition ascribes a disposition to the real knower to believe all and only justified propositions in virtue of his/her belief that the propositions are justified. Two consequences of that requirement are discussed: (1) if S really knows that p, then S knows simpliciter that S knows simpliciter that p and (2) the iterative feature of real knowledge mentioned in (1) provides a basis for the rejection of a particularly pernicious form of scepticism. (shrink)

Rich with historical and cultural value, these works are published unaltered from the original University of Minnesota Press editions.

There have been many attempts of late to formulate a satisfactory theory of knowledge with which to replace the traditional justified true belief analysis. Almost all agree that it must be the case that in order for S to know that p; i.) p be true, and ii.) S believe that p. Although many argue that there must be a condition stating that S has adequate evidence for p, requirements other than i.) and ii.) are controversial. The most popular approach (...) taken, however, is the addition of a requirement to the effect that for S to know that p there must be no other evidence against p strong enough to undermine S's belief that p, should this evidence come to S's attention. I shall call such a requirement a “defeasibility condition” and any theory containing such a requirement a defeasibility theory.Defeasibility theories are quite effective in handling a certain kind of difficulty to which theories of knowledge are subject, namely problems dealing with what Harman has termed the social aspect of knowledge. (shrink)

The recently offered, Purported counter-Examples to justified, True belief analyses of knowledge are looked at with some care and all found to be either incoherent or inconclusive. It is argued that justified, True belief analyses are based on sound insight into the concept of knowledge. The distinction between having been justified in claiming to know something and actually having known it is used in an effort to get the discussion of knowledge back on the right track.