Willem Blok and Modal Logic

We present our personal view on W.J. Blok's contribution to modal logic.     

A Formal Characterisation of Hamblin’s Action-State Semantics

Hamblin’s Action-State Semantics provides a sound philosophical foundation for understanding the character of the imperative. Taking this as our inspiration, in this paper we present a logic of action, which we call ST, that captures the clear ontological distinction between being responsible for the achievement of a state of affairs and being responsible for the performance of an action. We argue that a relativised modal logic of type RT founded upon a ternary relation over possible worlds integrated with a basic tense logic captures intuitions of the Hamblinian model of imperatives. The logic implements a direct mapping of each of Hamblin’s key concepts: strategies, partial strategies and wholehearted satisfaction.     

The Relevant Equivalence Property

The pure implicational and the multiplicative fragments of arange of propositional relevant (and other) logics are shownto have the property that any two formulas equivalent in sucha logic are constructed from exactly the same propositionalvariables – as opposed to merely having (as the definitionof relevance itself would require) some propositional variablein common.     

Combinatory Logic and the Semantics of Substructural Logics

The results of this paper extend some of the intimate relations that are known to obtain between combinatory logic and certain substructural logics to establish a general characterization theorem that applies to a very broad family of such logics. In particular, I demonstrate that, for every combinator X, if LX is the logic that results by adding the set of types assigned to X (in an appropriate type assignment system, TAS) as axioms to the basic positive relevant logic B∘T, then LX is sound and complete with respect to the class of frames in the Routley-Meyer relational semantics for relevant and substructural logics that meet a first-order condition that corresponds in a very direct way to the structure of the combinator X itself. Presented by Rob Goldblatt     

Two for the show: Anti-luck and virtue epistemologies in consonance

This essay extends my side of a discussion begun earlier with Duncan Pritchard, the recent author of Epistemic Luck.Pritchard’s work contributes significantly to improving the “diagnostic appeal” of a neo-Moorean philosophical response to radical scepticism. While agreeing with Pritchard in many respects, the paper questions the need for his concession to the sceptic that the neo-Moorean is capable at best of recovering “‘brute’ externalist knowledge”. The paper discusses and directly responds to a dilemma that Pritchard poses for virtue epistemologies (VE). It also takes issue with Pritchard’s “merely safety-based” alternative. Ultimately, however, the criticisms made here of Pritchard’s dilemma and its underlying contrast of “anti-luck” and “virtue” epistemologies are intended to help realize his own aspirations for a better diagnosis of radical scepticism to inform a still better neo-Moorean response.     

Analytic Tableau Systems and Interpolation for the Modal Logics KB, KDB, K5, KD5

We give complete sequent-like tableau systems for the modal logics KB, KDB, K5, and KD5. Analytic cut rules are used to obtain the completeness. Our systems have the analytic superformula property and can thus give a decision procedure. Using the systems, we prove the Craig interpolation lemma for the mentioned logics.     

Knowledge-telling and knowledge-transforming arguments in mock jurors' verdict justifications

According to the “story model” a juror constructs an implicit mental model of a story telling what happened as the basis for the verdict choice. But the explicit justification of a verdict choice could take the form of a story (knowledge telling) or the form of a relational (knowledge-transforming) argument structure that brings together diverse, non-chronologically related pieces of evidence. The study investigates whether people tend towards knowledge telling or knowledge transforming, and whether use of these argument structure types are related to skilled argument and epistemic understanding. A sample of people on jury duty chose and justified verdicts in two abridged cases. Participants tended to display the same argument structure and argument skill across cases. Those using knowledge-transforming structures were more successful at the juror argument skills task and had a higher level of epistemic understanding. The discussion suggests that jurors approach their task with an epistemic orientation towards knowledge telling or knowledge transforming.     

Adults see vision to be more informative than it is

Humans gain a wide range of knowledge through interacting with the environment. Each aspect of our perceptual experiences offers a unique source of information about the world—colours are seen, sounds heard and textures felt. Understanding how perceptual input provides a basis for knowledge is thus central to understanding one's own and others' epistemic states. Developmental research suggests that 5-year-olds have an immature understanding of knowledge sources and that they overestimate the knowledge to be gained from looking. Without evidence from adults, it is not clear whether the mature reasoning system outgrows this overestimation. The current study is the first to investigate whether an overestimation of the knowledge to be gained from vision occurs in adults. Novel response time paradigms were adapted from developmental studies. In two experiments, participants judged whether an object or feature could be identified by performing a specific action. Adult participants found it disproportionately easy to accept looking as a proposed action when it was informative, and difficult to reject looking when it was not informative. This suggests that adults, like children, overestimate the informativeness of vision. The origin of this overestimation and the implications that the current findings bear on the interpretation of children's overestimation are discussed.