Knowledge: Undefeated Justified True Belief

Lehrer, Keith; Paxson, Thomas D.

doi:10.2307/2024435

Cited by 408 publications

(121 citation statements)

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“…Various authors identify this missing ingredient as "robustness" (Hintikka [34]), "indefeasibility" (Klein [37], Lehrer [39], Lehrer and Paxson [40], Stalnaker [51]) or "stability" (Rott [45]). According to this defeasibility theory of knowledge (or "stability theory", as formulated by Rott), a belief counts as "knowledge" if it is stable under belief revision with any new evidence: "if a person has knowledge, than that person's justification must be sufficiently strong that it is not capable of being defeated by evidence that he does not possess" (Pappas and Swain [42]).…”

Section: Safe Belief and The Defeasibility Theory Of Knowledgementioning

confidence: 99%

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A Qualitative Theory of Dynamic Interactive Belief Revision

Baltag

Smets

2016

Readings in Formal Epistemology

177

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We present a logical setting that incorporates a belief-revision mechanism within Dynamic-Epistemic logic. As the "static" basis for belief revision, we use epistemic plausibility models, together with a modal language based on two epistemic operators: a "knowledge" modality K (the standard S5, fully introspective, notion), and a "safe belief" modality 2 ("weak", non-negatively-introspective, notion, capturing a version of Lehrer's "indefeasible knowledge"). To deal with "dynamic" belief revision, we introduce action plausibility models, representing various types of "doxastic events". Action models "act" on state models via a modified update product operation: the "ActionPriority" Update. This is the natural dynamic generalization of AGM revision, giving priority to the incoming information (i.e. to "actions") over prior beliefs. We completely axiomatize this logic, and show how our update mechanism can "simulate", in a uniform manner, many different belief-revision policies.

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Section: Safe Belief and The Defeasibility Theory Of Knowledgementioning

confidence: 99%

“…The most important such notion expresses a form of "weak (non-introspective) knowledge" 2 a P , first introduced by Stalnaker in his modal formalization [49,51] of Lehrer's defeasibility analysis of knowledge [39,40]. We call this notion safe belief, to distinguish it from our (Aumann-type) concept of knowledge.…”

Section: Introductionmentioning

confidence: 99%

A Qualitative Theory of Dynamic Interactive Belief Revision

Baltag

Smets

2016

Readings in Formal Epistemology

177

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“…Facts of this 'belief-blocking' kind are known in the philosophical literature as 'defeaters'. Insisting that authentic evidence be free of all defeaters is a very strong condition indeed, because it would even rule out ordinary perception in ideal circumstances as long as some misleading contrary evidence could potentially be collected against it (Lehrer & Paxson, 1969). If we take this proposed 'no-defeater' condition at face value, having authentic evidence for the proposition p would require knowing that p on an especially stringent understanding of 'knowledge'.…”

Section: The Contrast Between Apparent and Authentic Evidencementioning

confidence: 99%

Authentic Gettier cases: A reply to Starmans and Friedman

2013

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Do laypeople and philosophers differ in their attributions of knowledge? Starmans and Friedman maintain that laypeople differ from philosophers in taking 'authentic evidence' Gettier cases to be cases of knowledge. Their reply helpfully clarifies the distinction between 'authentic evidence' and 'apparent evidence'. Using their sharpened presentation of this distinction, we contend that the argument of our original paper still stands.We would like to thank Starmans and Friedman (this issue) for their careful reading of our paper and for opening up a broader discussion regarding how some of the divergent findings that have emerged in this area might be reconciled. It is important to recognize that we all agree on a core point: both philosophers and laypeople take some Gettier cases to exemplify justified true belief without knowledge. Where we appear to differ is on the question of whether laypeople respond differently to a special subset of these cases. Starmans and Friedman maintain that 'authentic evidence' Gettier cases are seen as cases of knowledge by laypeople but not by philosophers, whereas our data do not support this assertion (Nagel, San Juan, & Mar, this issue). In their reply to our article, Starmans and Friedman raise three concerns: (1) we misconstrued their contrast between authentic and apparent evidence, (2) the authentic evidence cases we used were atypical of Gettier cases in general; and (3) our methods of questioning biased participants to deny knowledge. These three concerns are potentially quite damning and we are grateful for the opportunity to address them here. On the first point, we appreciate the clarification provided by

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“…This is the "defeasibility strategy", followed by many of those who attempted to respond to Gettier's challenge, see e.g Lehrer and Paxson [53], Swain [91], Stalnaker [87,88]. To quote Stalnaker [88], "the idea was that the fourth condition (to be added to justified true belief) should be a requirement that there would be no 'defeater' -no true proposition that, if the knower learned that it was true, would lead her to give up the belief, or to be no longer justified in holding it".…”

Section: Other Notions Of Knowledgementioning

confidence: 99%