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Author Information: Jonathan Matheson & Valerie Joly Chock, University of North Florida,

Matheson, Jonathan; Valerie Joly Chock. “Knowledge and Entailment: A Review of Jessica Brown’s Fallibilism: Evidence and Knowledge.” Social Epistemology Review and Reply Collective 7, no. 10 (2018): 55-58.

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Jessica Brown’s Fallibilism is an exemplary piece of analytic philosophy. In it, Brown engages a number of significant debates in contemporary epistemology with the aim of making a case for fallibilism about knowledge. The book is divided into two halves. In the first half (ch. 1-4), Brown raises a number of challenges to infallibilism. In the second half (ch. 5-8), Brown responds to challenges to fallibilism. Brown’s overall argument is that since fallibilism is more intuitively plausible than infallibilism, and since it fares no worse in terms of responding to the main objections, we should endorse fallibilism.

What Is Fallibilism?

In the introductory chapter, Brown distinguishes between fallibilism and infallibilism. According to her, infallibilism is the claim that one knows that p only if one’s evidence entails p, whereas fallibilism denies this. Brown settles on this definition after having examined some motivation and objections to other plausible definitions of infallibilism. With these definitions in hand, the chapter turns to examine some motivation for fallibilism and infallibilism.

Brown then argues that infallibilists face a trilemma: skepticism, shifty views of knowledge, or generous accounts of knowledge. Put differently, infallibilists must either reject that we know a great deal of what we think we know (since our evidence rarely seems to entail what we take ourselves to know), embrace a view about knowledge where the standards for knowledge, or knowledge ascriptions, vary with context, or include states of the world as part of our evidence. Brown notes that her focus is on non-skeptical infallibilist accounts, and explains why she restricts her attention in the remainder of the book to infallibilist views with generous conception of evidence.

In chapter 2, Brown lays the groundwork for her argument against infallibilism by demonstrating some commitments of non-skeptical infallibilists. In order to avoid skepticism, infallibilists must show that we have evidence that entails what we know. In order to do so, they must commit to certain claims regarding the nature of evidence and evidential support.

Brown argues that non-factive accounts of evidence are not suitable for defending infallibilism, and that infallibilists must embrace an externalist, factive account of evidence on which knowing that p is sufficient for p to be part of one’s evidence. That is, infallibilists need to endorse Factivity (p is evidence only if p is true) and the Sufficiency of knowledge for evidence (if one knows that p, then p is part of one’s evidence).

However, Brown argues, this is insufficient for infallibilists to avoid skepticism in cases of knowledge by testimony, inference to the best explanation, and enumerative induction. In addition, infallibilists are committed to the claim that if one knows p, then p is part of one’s evidence for p (the Sufficiency of knowledge for self-support thesis).

Sufficiency of Knowledge to Support Itself

Chapter 3 examines the Sufficiency of knowledge for self-support in more detail. Brown begins by examining how the infallibilist may motivate this thesis by appealing to a probabilistic account of evidential support. If probability raisers are evidence, then there is some reason to think that every proposition is evidence for itself.

The main problem for the thesis surrounds the infelicity of citing p as evidence for p. In the bulk of the chapter, Brown examines how the infallibilist may account for this infelicity by appealing to pragmatic explanations, conversational norms, or an error theory. Finding each of these explanations insufficient to explain the infelicity here, Brown concludes that the infallibilist’s commitment to the Sufficiency of knowledge for self-support thesis is indeed problematic.

Brown takes on the infallibilists’ conception of evidence in Chapter 4. As mentioned above, the infallibilist is committed to a factive account of evidence, where knowledge suffices for evidence. The central problem here is that such an account has it that intuitively equally justified agents (one in a good case and one in a bad case) are not in fact equally justified.

Brown then examines the ‘excuse maneuver’, which claims that the subject in the bad case is unjustified yet blameless in their belief, and the original intuition confuses these assessments. The excuse maneuver relies on the claim that knowledge is the norm of belief. Brown argues that the knowledge norm fails to provide comparative evaluations of epistemic positions where subjects are intuitively more or less justified, and fails to give an adequate account of propositional justification when the target proposition is not believed. In addition, Brown argues that extant accounts of what would provide the subject in the bad case with an excuse are all insufficient.

In Chapter 5 the book turns to defending fallibilism. The first challenge to fallibilism that Brown examines concerns closure. Fallibilism presents a threat to multi-premise closure since one could meet the threshold for knowledge regarding each individual premise, yet fail to meet it regarding the conclusion. Brown argues that giving up on closure is no cost to fallibilists since closure ought to be rejected on independent grounds having to do with defeat.

A subject can know the premises and deduce the conclusion from them, yet have a defeater (undercutting or rebutting) that prevents the subject from knowing the conclusion. Brown then defends such defeat counterexamples to closure from a number of recent objections to the very notion of defeat.

Chapter 6 focuses on undermining defeat and recent challenges that come to it from ‘level-splitting’ views. According to level-splitting views, rational akrasia is possible—i.e., it is possible to be rational in simultaneously believing both p and that your evidence does not support p. Brown argues that level-splitting views face problems when applied to theoretical and practical reasoning. She then examines and rejects attempts to respond to these objections to level-splitting views.

Brown considers objections to fallibilism from practical reasoning and the infelicity of concessive knowledge attributions in Chapter 7. She argues that these challenges are not limited to fallibilism but that they also present a problem for infallibilism. In particular, Brown examines how (fallibilist or infallibilist) non-skeptical views have difficulty accommodating the knowledge norm for practical reasoning (KNPR) in high-stakes cases.

She considers two possible responses: to reject KNPR or to maintain KNPR by means of explain-away maneuvers. Brown claims that one’s response is related to the notion of probability one takes as relevant to practical reasoning. According to her, fallibilists and infallibilists tend to respond differently to the challenge from practical reasoning because they adopt different views of probability.

However, Brown argues, both responses to the challenge are in principle available to each because it is compatible with their positions to adopt the alternative view of probability. Thus, Brown concludes that practical reasoning and concessive knowledge attributions do not provide reasons to prefer infallibilism over fallibilism, or vice versa.

Keen Focus, Insightful Eyes

Fallibilism is an exemplary piece of analytic philosophy. Brown is characteristically clear and accessible throughout. This book will be very much enjoyed by anyone interested in epistemology. Brown makes significant contributions to contemporary debates, making this a must read for anyone engaged in these epistemological issues. It is difficult to find much to resist in this book.

The arguments do not overstep and the central thesis is both narrow and modest. It’s worth emphasizing here that Brown does not argue that fallibilism is preferable to infallibilism tout court, but only that it is preferable to a very particular kind of infallibilism: non-skeptical, non-shifty infallibilism.  So, while the arguments are quite strong, the target is more narrow.

One of the central arguments against fallibilism that Brown considers concerns closure. While she distinguishes multi-premise closure from single-premise closure, the problems for fallibilism concern only the former, which she formulates as follows:

Necessarily, if S knows p1-n, competently deduces, and thereby comes to believe q, while retaining her knowledge of p1-n throughout, then S knows q. (101)

The fallibilist threshold condition is that knowledge that p requires that the probability of p on one’s evidence be greater than some threshold less than 1. This threshold condition generates counterexamples to multiple-premise closure in which S fails to know a proposition entailed by other propositions she knows. Where S’s evidence for each premise gives them a probability that meets the threshold, S knows each of the premises.

If together these premises entail q, then S knows premises p1-n that jointly entail conclusion q. The problem is that S knowing the premises in this way is compatible with the probability of the conclusion on S’s evidence not meeting the threshold. Thus, this presents possibility for counterexamples to closure and a problem for fallibilism.

As the argument goes, fallibilists must deny closure and this is a significant cost. Brown’s reply is to soften the consequence of denying closure by arguing that it is implausible due to alternative (and independent) reasons concerning defeat. Brown’s idea is that closure gives no reason to reject fallibilism, or favor infallibilism, given that defeat rules out closure in a way that is independent of the fallibilism-infallibilism debate.

After laying out her response, Brown moves on to consider and reply to objections concerning the legitimacy of defeat itself. She ultimately focuses on defending defeat against such objections and ignores other responses that may be available to fallibilists when dealing with this problem. Brown, though, is perhaps a little too quick to give up on closure.

Consider the following alternative framing of closure:

If S knows [p and p entails q] and believes q as the result of a competent deduction from that knowledge, then S knows q.

So understood, when there are multiple premises, closure only applies when the subject knows the conjunction of the premises and that the premises entail the conclusion. Framing closure in this way avoids the threshold problem (since the conjunction must be known). If S knows the conjunction and believes q (as the result of competent deduction), then S’s belief that q cannot be false. This is the case because the truth of p entailing q, coupled with the truth of p itself, guarantees that q is true. This framing of closure, then, eliminates the considered counterexamples.

Framing closure in this way not only avoids the threshold problem, but plausibly avoids the defeat problem as well. Regarding undercutting defeat, it is at least much harder to see how S can know that p entails q while possessing such a defeater. Regarding rebutting defeat, it is implausible that S would retain knowledge of the conjunction if S possesses a rebutting defeater.

However, none of this is a real problem for Brown’s argument. It simply seems that she has ignored some possible lines of response open to the fallibilist that allows the fallibilist to keep some principle in the neighborhood of closure, which is an intuitive advantage.

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Brown, Jessica. Fallibilism: Evidence and Knowledge. Oxford: Oxford University Press, 2018.

Author Information: Stefano Bigliardi, Foundation for Interreligious and Intercultural Research and Dialogue, Geneva; Center for Middle Eastern Studies, Lund University; ITESM Campus Santa Fe, Mexico City,

Bigliardi, Stefano. “I’Jāz, Conspiracy Theories, and Ufology—Some Suggestions with a Touch of Latour.” Social Epistemology Review and Reply Collective 4, no. 11 (2015): 1-7.

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