Igor Sedlár

The paper relates evidence and justification logics, both philosophically and technically. On the philosophical side, it is suggested that the difference between the approaches to evidence in the two families of logics can be explained as a result of their focusing on two different notions of support provided by evidence. On the technical side, a justification logic with operators pertaining to both kinds of support is shown to be sound and complete with respect to a special class of awareness models. In addition, a realization theorem with respect to K is shown to hold for the logic.

The paper offers an argument against Kripke’s assertion, that it is valid for all names of natural species, that they have no connotations. The argumentation has is roots in the semantic conception of S. Kripke as articulated in his Naming and necessity. i.e., it is an „argument from inside“ the conception itself. The argument consists of two parts: setting the conditions under which the name of a natural species has a connotation; constructing a situation, in which these conditions are fulfilled

The paper outlines a generalisation of the awareness-based epistemic semantics by Fagin and Halpern. Awareness is construed as a relation between agents and pieces of information instead of formulas. The main motive for introducing the generalisation is that it shows substructural logics to be a natural component of information-based epistemic logic: substructural logics can be seen as describing the logical behaviour of pieces of information. Substructural epistemic logics are introduced and some of their properties are discussed. In addition, extensions of substructural epistemic logics invoking group-epistemic and dynamic modalities are sketched.

Pavel Cmorej has argued that the existence of unverifiable and unfalsifiable empirical propositions follows from certain plausible assumptions concerning the notions of possibility and verification. Cmorej proves, it the context of a bi-modal alethic-epistemic axiom system AM4, that (1) p and it is not verified that p is unverifiable; (2) p or it is falsified that p is unfalsifiable; (3) every unverifiable p is logically equivalent to p and it is not verifiable that p; (4) every unverifiable p entails that p is unverifiable. This article elaborates on Cmorej’s results in three ways. Firstly, we formulate a version of neighbourhood semantics for AM4 and prove completeness. This allows us to replace Cmorej’s axiomatic derivations with simple model-theoretic arguments. Secondly, we link Cmorej’s results to two well-known paradoxes, namely Moore’s Paradox and the Knowability Paradox. Thirdly, we generalise Cmorej’s results, show them to be independent of each other and argue that results (3) and (4) are independent of any assumptions concerning the notion of verification.

The paper provides an alternative interpretation of ‘pair points’, discussed in Beall et al., "On the ternary relation and conditionality", J. of Philosophical Logic 41(3), 595-612. Pair points are seen as points viewed from two different ‘perspectives’ and the latter are explicated in terms of two independent valuations. The interpretation is developed into a semantics using pairs of Kripke models (‘pair models’). It is demonstrated that, if certain conditions are fulfilled, pair models are validity-preserving copies of positive substructural models. This yields a general soundness and completeness result for a variety of (positive) substructural logics with respect to multimodal Kripke frames with binary accessibility relations. In addition, an epistemic interpretation of pair models is provided.

The primary aim of the paper is to introduce a new notion of relevance of the antecedent of a true implication statement to its consequent, and to sketch a formalization of the new notion. The formalization is set up in the framework of the so called Logic of Strict Processes , as articulated by the author in collaboration with J. Podroužek. Their approach to the relevance is presented as a natural part of a wider specter of logics, including modal and relevance logics. The formalization is compared with consequence relations in normal modal logic and in the relevance logic R. In conclusion the author outlines the most important problems of LSP, which still remain open