Knowledge and epistemic necessity

2019

The philosophically popular name of 'epistemic possibility' is a misnomer and the ideas based on it are mistaken. ~ White (1975, 86

Principia: an international journal of epistemology, 2010

Although epistemic possibility figures in several debates, those debates have had relatively little contact with one another. G. E. Moore focused squarely upon analyzing epistemic uses of the phrase, 'It's possible that p', and in doing so he made two fundamental assumptions. First, he assumed that epistemic possibility statements always express the epistemic position of a community, as opposed to that of an individual speaker. Second, he assumed that all epistemic uses of 'It's possible that p' are analyzable in terms of knowledge, not belief. A number of later theorists, including Keith DeRose, provide alternative accounts of epistemic possibility, while retaining Moore's two assumptions. Neither assumption has been explicitly challenged, but Jaakko Hintikka's analysis provides a basis for doing so. Drawing upon Hintikka's analysis, I argue that some epistemic possibility statements express only the speaker's individual epistemic state, and that contra DeRose, they are not degenerate community statements but a class in their own right. I further argue that some linguistic contexts are belief-rather than knowledge-based, and in such contexts, what is possible for a speaker depends not upon what she knows, but upon what she believes.

KRITERION – Journal of Philosophy

I am concerned with epistemic possibility expressions (EPEs) such as \It might be raining." Much of the discussion of EPEs has concerned the fact that a given EPE can seem true in one context and false in another. Motivated by this data, contextualists have argued that modal expressions are sensitive to information at a context of use. Contextualist analyses encounter problems when it comes to disagreements centered on EPEs. Relativists such as John Mac- Farlane argue that epistemic modals are sensitive to information available to an assessor at a circumstance of evaluation. I side with a relativistic account of epistemic possibility, on which the truth conditions of EPEs depend not only on a context of use but also as on a context of assessment. The stipulation of contexts of assessments explains why third parties can judge an interlocutor's utterance false, and why the interlocutor will retract her previous utterance. However, judgements of falsity and retraction seem to ...

In spite of an evolving contemporary debate over the concept of “epistemic possibility,” nearly every philosopher assumes that the concept is equivalent to a mere absence of epistemic impossibility, that a proposition is epistemically possible as long as it is not inconsistent with some relevant body of knowledge. I suggest that we challenge this deeply entrenched assumption. I assemble an array of data that singles out the distinctive meaning and function of the attitude of taking propositions as epistemically possible, and suggest that this data is best explained by a positive evidentialist conception of epistemic possibility. On this conception, a proposition is epistemically possible to a subject if and only if the subject has cognitive access to evidence that specifically supports that proposition.

Philosophia, 1974

How much can we turn the screw on counter-examples to the KK principle? The principle, also sometimes called “positive introspection”, says that if one knows that P, one knows that one knows that P. It is widely, although not universally, acknowledged that the KK principle is false, and not just for the boring reason that one can know that P without having formed the belief that one knows that P. One can know that P, and believe that one knows that P, without knowing that one knows that P, because one is not in a strong enough epistemic ...

… manuscript, University of …, 2010

Most epistemologists hold that knowledge entails belief. However, proponents of this claim rarely offer a positive argument in support of it. Rather, they tend to treat the view as obvious and assert that there are no convincing counterexamples. We find this strategy to be problematic. We do not find the standard view obvious, and moreover, we think there are cases in which it is intuitively plausible that a subject knows some proposition P without -or at least without determinately -believing that P. Accordingly, we present five plausible examples of knowledge without (determinate) belief, and we present empirical evidence suggesting that our intuitions about these scenarios are not atypical.

Synthese 2010, Vol. 174, 385-395.

Recently, Yalcin (2007) put forward a novel account of epistemic modals. It is based on the observation that sentences of the form `&Might:' do not embed under `suppose' and `if'. Yalcin concludes that such sentences must be contradictory and develops a notion of informational consequence which validates this idea. I will show that informational consequence is inadequate as an account of the logic of epistemic modals: it cannot deal with reasoning from uncertain premises. Finally, I o er an alternative way of explaining the relevant linguistic data.

Journal of Philosophy, 2015

Many epistemologists call themselves ‘fallibilists’. But many philosophers of language hold that the meaning of epistemic usages of ‘possible’ ensures a close knowledge-(epistemic) possibility link (KPL): a subject’s utterance of ‘it’s possible that not-p’ is true only if the subject does not know that p. This seems to suggest that whatever the core insight behind fallibilism is, it can’t be that a subject could have knowledge which is, for them, possibly false. I argue that, on the contrary, subjects can have such possibly false knowledge. My ultimate aim, then, is to vindicate a very robust form of fallibilism. Uniquely, however, the account I offer does this while also allowing that concessive knowledge attributions – sentences of the form “I know that p, but it’s possible that not-p” – are not only infelicitous but actually false whenever uttered. The account predicts this result without conceding KPL. I argue that my account has the resources to explain some related cases for which the KPL account yields the wrong predictions. Taken as a whole, the linguistic data not only do not support the proposal that subjects cannot have possibly false knowledge, but indeed positively favor the proposal that they can.

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).