Justified True Belief Is Knowledge

Kritike: An Online Journal of Philosophy, 2018

In this paper, we contend that the "Smith case" in Gettier's attempt to refute the justified true belief (JTB) account of knowledge does not work. This is because the said case fails to satisfy the truth condition, and thus is not a case of JTB at all. We demonstrate this claim using the framework of Donnellan's distinction between the referential and attributive uses of definite descriptions. Accordingly, the truth value of Smith's proposition "The man who will get the job has ten coins in his pocket" partly depends on how Smith uses the definite description "the man who will get the job" when he utters the proposition. Since, upon uttering the proposition, Smith has in mind a particular individual, namely Jones, and not just whoever will fit the attribute specified in the definite description, Smith uses the definite description referentially. And so when it turns out that it is Smith who eventually gets the job, the definite description fails to refer to Jones as intended by Smith, thereby making Smith's proposition false. To think that Smith's proposition is still true, in this regard, is to use the definite description attributively-that it is about whoever will fit the definite description. Apparently, when Gettier claims that Smith's proposition is still true, to demonstrate that it is a case of JTB, he, in effect, imposes his attributive understanding of Smith's usage of the definite description on Smith's own epistemic situation.

Aspects of Knowing: Epistemological Essays, 2006

Abstract: The possibility of justified true belief without knowledge is normally motivated by informally classified examples. This paper shows that it can also be motivated more formally, by a natural class of epistemic models in which both knowledge and justified belief (in the relevant sense) are represented. The models involve a distinction between appearance and reality. Gettier cases arise because the agent's ignorance increases as the gap between appearance and reality widens.

Grazer Philosophische Studien

Edmund Gettier (1963) argued that there can be justified true belief (JTB) that is not knowledge. The correctness of Gettier’s argument is questioned by showing that Smith of Gettier's famous examples does not earn justification for his incidentally true beliefs, while a doxastically more conscientious person S would come to hold justified but false beliefs. So, Gettier’s (and analogous) cases do not result in justified and true belief. This is due to a tension between deductive closure of justification and evidential support. For being justified, any believing, disbelieving, or withholding of deductively inferred propositions must be distributed proportionally to given evidential support. This proportionality principle has primacy over deductive closure in case of conflict. Although the argument does not save the JTB-account, it explains why the intuition that subjects in Gettier situations do not earn knowledge is correct.

Philosophia, 1982

Section 1 : Introduction One of the first responses to Gettier's original paper was the suggestion made by Michael Clark [4] that S knows that p only if all of S's evidence for p is true. It soon became clear, however, 1 that this analysis was too strong for it precluded S from knowing even if a sufficient part of his evidence was true while part was false. We might then think of requiring only that p be justified for S on the basis of a set of evidence limited to only true statements. However, examples like Skyrms' barometer case [16] made it appear that this view wouldn't do either. Skyrms asks us to consider a person, S, who infers that it will rain from the statement (1) The barometer has fallen as a result of a drop in atmospheric pressure. But it happens that, though it will rain, the fall in the barometer is occasioned not by a drop in atmospheric pressure but by the fact that (2) There is a malfunction in the barometer. Our intuition here is that the person fails to know that rain will fall, though he is justified in believing that it will. Though the causal premise, (l), is false there is available to S a set of true premises, i.e. (3) It is likely that when the barometer falls, it will rain. and (4) The barometer has fallen

The possibility of justified true belief without knowledge is normally motivated by informally classified examples. This paper shows that it can also be motivated more formally, by a natural class of epistemic models in which both knowledge and justified belief (in the relevant sense) are represented. The models involve a distinction between appearance and reality. Gettier cases arise because the agent’s ignorance increases as the gap between appearance and reality widens. The models also exhibit an epistemic asymmetry between good and bad cases that sceptics seem to ignore or deny.

Philosophical Perspectives, 2012

The Philosophical Quarterly, 2009

Springer eBooks, 2003

The aims of this paper are (i) to summarize the semantics of (the propositional part of) a unified epistemic/doxastic logic as it has been developed at greater length in Lenzen [1980] and (ii) to use some of these principles for the development of a semi-formal pragmatics of epistemic sentences. While a semantic investigation of epistemic attitudes has to elaborate the truth-conditions for, and the analytically true relations between, the fundamental notions of belief, knowledge, and conviction, a pragmatic investigation instead has to analyse the specific conditions of rational utterance or utterability of epistemic sentences. Some people might think that both tasks coincide. According to Wittgenstein, e.g., the meaning of a word or a phrase is nothing else but its use (say, within a certain community of speakers). Therefore the pragmatic conditions of utterance of words or sentences are assumed to determine the meaning of the corresponding expressions. One point I wish to make here, however, is that one may elaborate the meaning of epistemic expressions in a way that is largely independent of-and, indeed, even partly incompatible with-the pragmatic conditions of utterability. Furthermore, the crucial differences between the pragmatics and the semantics of epistemic expressions can satisfactorily be explained by means of some general principles of communication. In the first three sections of this paper the logic (or semantics) of the epistemic attitudes belief, knowledge, and conviction will be sketched. In the fourth section the basic idea of a general pragmatics will be developed which can then be applied to epistemic utterances in particular. 1 The Logic of Conviction Let 'C(a,p)' abbreviate the fact that person a is firmly convinced that p, i.e. that a considers the proposition p (or, equivalently, the state of affairs expressed by that proposition) as absolutely certain; in other words, p has maximal likelihood or probability for a. Using 'Prob' as a symbol for subjective probability functions, this idea can be formalized by the requirement: (PROB-C) C(a,p) ↔ Prob(a,p)=1. Within the framework of standard possible-worlds semantics <I,R,V>, C(a,p) would have to be interpreted by the following condition: (POSS-C) V(i,C(a,p))=t ↔ ∀j(iRj → V(j,p)=t). Here I is a non-empty set of (indices of) possible worlds; R is a binary relation on I such that iRj holds iff, in world i, a considers world j as possible; and V is a valuation-function assigning to each proposition p relative to each world i a truth-value V(i,p)∈{t,f}. Thus C(a,p) is true (in world i∈I) iff p itself is true in every possible world j which is considered by a as possible (relative to i). The probabilistic "definition" POSS-C together with some elementary theorems of the theory of subjective probability immediately entails the validity of the subsequent laws of conjunction and non-contradiction. If a is convinced both of p and of q, then a must also be convinced that p and q: (C1) C(a,p) ∧ C(a,q) → C(a,p∧q). For if both Prob(a,p) and Prob(a,q) are equal to 1, then it follows that Prob(a,p∧q)=1, too. Furthermore, if a is convinced that p (is true), a cannot be convinced that ¬p, i.e. that p is false: (C2) C(a,p) → ¬C(a,¬p). For if Prob(a,p)=1, then Prob(a,¬p)=0, and hence Prob(a,¬p)≠1. Just like the alethic modal operators of possibility, ◊, and necessity, , are linked by the relation ◊p ↔ ¬ ¬p, so also the doxastic modalities of thinking p to be possible-formally: P(a,p)-and of being convinced that p, C(a,p), satisfy the relation (Def. P) P(a,p) ↔ ¬C(a,¬p). Thus, from the probabilistic point of view, P(a,p) holds iff a assigns to the proposition p (or to the event expressed by that proposition) a likelihood greater than 0: (PROB-P) V(P(a,p))=t ↔ Prob(a,p)>0. Within the framework of possible-worlds semantics, one obtains the following condition: (POSS-P) V(i,P(a,p))=t ↔ ∃j(iRj ∧ V(j,p)=t), according to which P(a,p) is true in world i iff there is at least one possible world j-i.e. a world j accessible from i-in which p is true. 1 Cf., e.g., Hintikka [1970]. 2 Clearly, since C(a,p) ∨ ¬C(a,p) holds tautologically, C10 and C11 entail that C(a,C(a,p)) ∨ C(a,¬C(a,p)) is epistemic-logically true. So either way there exists a q such that C(a,q).