Some philosophical aspects of reasoning about knowledge

Philosophical Writings, 2014

It is largely admitted that the tripartite conception as Justified True Belief knowledge implying truth is possible but truth is not recognisable per se, that is, knowledge implying self-awareness of having the truth (which is not to be conflated with certainty) is impossible. Borrowing from the theory of meaning I intend to redefine knowledge with the immanence principle and the implicitness principle, which impose the recognisability of the knowledge conditions. Second, I argue that since truth is not directly recognisable it must be inferred. Hence, knowledge is the product of an inference from a belief and a justification to the truthascription of the henceforth-acknowledged belief. The seminal Gettier problems take thus an almost trivial aspect, or at least it is no obstacle to the possibility of knowledge thus defined.

Journal of Logic and Computation, 2015

In this article, we introduce an epistemic modal operator modelling knowledge over distributive non-associative full Lambek calculus with a negation. Our approach is based on the relational semantics for substructural logics: we interpret the elements of a relational frame as information states consisting of collections of data. The principal epistemic relation between the states is the one of being a reliable source of information, on the basis of which we explicate the notion of knowledge as information confirmed by a reliable source. From this point of view it is natural to define the epistemic operator formally as the backward-looking diamond modality. The framework is a generalization and extension of the system of relevant epistemic logic proposed by Majer and Peliš (2009, college Publications, 123-135) and developed by Bílková et al. (2010, college Publications, 22-38). The system is modular in the sense that the axiomatization of the epistemic operator is sound and complete with respect to a wide class of background logics, which makes the system potentially applicable to a wide class of epistemic contexts. Our system admits a weak form of logical omniscience (the monotonicity rule), but avoids stronger ones (a necessitation rule and a K-axiom) as well as some closure properties discussed in normal epistemic logics (like positive and negative introspection). For these properties we provide characteristic frame conditions, so that they can be present in the system if they are considered to be appropriate for some specific epistemic context. We also prove decidability of the weakest epistemic logic we consider, using a filtration method. Finally, we outline further extensions of our framework to a multiagent system.

Minds and Machines - MIND MACH, 1997

My book is about how-possible questions in epistemology. I focus on three such questions, 'How is knowledge of the external world possible?', 'How is knowledge of other minds possible?', and 'How is a priori knowledge possible?'. I explain how questions of this form arise and suggest how they should be answered. The basic idea is that we start by assuming that knowledge of the kind in question is possible but then encounter apparent obstacles to its existence or acquisition. So the issue is: how is knowledge of such-and-such a kind possible given the factors that make it look impossible? Since such questions are obstacle-dependent a satisfying response will need to be an obstacle-removing response, one that shows how the obstacles that led to the question being asked in the first place can be overcome or dissipated.

Journal of Philosophical Logic, 2019

We propose a solution to the problem of logical omniscience in what we take to be its fundamental version: as concerning arbitrary agents and the knowledge attitude per se. Our logic of knowledge is a spin-off from a general theory of thick content, whereby the content of a sentence has two components: (i) an intension, taking care of truth conditions; and (ii) a topic, taking care of subject matter. We present a list of plausible logical validities and invalidities for the logic of knowledge per se for arbitrary agents, and isolate three explanatory factors for them: (1) the topic-sensitivity of content; (2) the fragmentation of knowledge states; (3) the defeasibility of knowledge acquisition. We then present a novel dynamic epistemic logic that yields precisely the desired validities and invalidities, for which we provide expressivity and completeness results. We contrast this with related systems and address possible objections.

Synthese, 2006

Where is the justificatory boundary between a true belief's not being knowledge and its being knowledge? Even if we put to one side the Gettier problem, this remains a fundamental epistemological question, concerning as it does the matter of whether we can provide some significant defence of the usual epistemological assumption that a belief is knowledge only if it is well justified. But can that question be answered non-arbitrarily? BonJour believes that it cannot be-and that epistemology should therefore abandon the concept of knowledge. More optimistically, this paper does attempt to answer that question, by applying-and thereby refining-a non-absolutist theory of knowledge.

Ratio, 2010

In this paper an improved formulation of the classical tripartite view of knowledge is proposed and defended. This formulation solves Gettier's problem by making explicit what is concealed by the symbolic version of the tripartite definition, namely, the perspectival context in which concrete knowledge claims are evaluated. Knowledge is not simply justified true belief, but it is justified true belief justifiably arrived at.

Philosophical Issues, 2008

What is the connection between knowledge and certainty? The question is vexed, in part because there are at least two distinct senses of "certainty". According to the first sense, subjective certainty, one is certain of a proposition if and only if one has the highest degree of confidence in its truth. According to the second sense of "certainty", which we may call epistemic certainty, one is certain of a proposition p if and only if one knows that p (or is in a position to know that p) on the basis of evidence that gives one the highest degree of justification for one's belief that p. The thesis that knowledge requires certainty in either of these two senses has been the basis for skeptical arguments. For example, according to one kind of skeptical argument, knowledge requires epistemic certainty, and being epistemically certain of a proposition requires having independent evidence that logically entails that proposition. Since we do not have such evidence for external world propositions, we do not know external world propositions. According to another kind of skeptical argument, due to Peter Unger (1975), knowledge requires subjective certainty, and we are never subjectively certain of any proposition. So, we never know any proposition. Some authors have responded to these skeptical arguments by adopting fallibilism about certainty, the doctrine that having the highest degree of justification for a belief does not involve the possession of logically entailing, non-question begging grounds for that belief (Miller (1978), Klein (1981, Chapter 3)). But my interest in this paper does not lie in rebutting skeptical arguments based upon the assumption that knowledge entails certainty. Rather, my purpose is to establish that knowledge does not require certainty in either of these two senses. Even if we are certain of many things, knowing that p does not entail subjective or epistemic certainty. Since the claim that knowledge requires certainty (in either sense) is closely associated with detrimental conclusions, the central case for the phis_136 phis2007.cls (1994/07/13 v1.2u Standard LaTeX document class) 7-22-2008 :809 Jason Stanley phis_136 phis2007.cls (1994/07/13 v1.2u Standard LaTeX document class) 7-22-2008 :809

Proceedings of the 10th conference on Theoretical …, 2005

Abstract: Two difficult issues for the logic of knowledge have been logical omniscience and common knowledge. Our existing logics of knowledge based on Kripke structures seem to justify logical omniscience, but we know that in real life it does not exist. Also, common knowledge ...