This paper aims to clarify the connection between the logic of temporal distinctions and the temporal features of propositions. Contra Prior, it argues that the adoption of tense operators does not commit one to the view that propositions can change their truth value over time.

In the article "Podstawy analizy metodologicznej kanonów Milla" [2] Jerzy Łoś proposed an operator that refered sentences to temporal moments. Let us look, for example, at a sentence ‘It is raining in Toruń’. From a logical point of view it is a propositional function, which does not have any logical value, unless we point at a temporal context from a fixed set of such contexts. If the sentence was considered today as a description of a state of affairs, it could (...) be true. If it was considered yesterday, it could be false. 1 The operator enables us to connect any sentence p with any temporal context t. Such a complex sentence we read as: a sentence p is realized at a temporal context t (a point of time, an interval of some kind, etc). (shrink)

The counterfactual and regularity theories are universal accounts of causation. I argue that these should be generalized to produce local accounts of causation. A hallmark of universal accounts of causation is the assumption that apparent variation in causation between locations must be explained by differences in background causal conditions, by features of the causal-nexus or causing-complex. The local account of causation presented here rejects this assumption, allowing for genuine variation in causation to be explained by differences in location. I argue (...) that local accounts of causation are plausible, and have pragmatic, empirical and theoretical advantages over universal accounts. I then report on the use of presheaves as models of local causation. The use of presheaves as models of local variation has precedents in algebraic geometry, category theory and physics; they are here used as models of local causal variation. The paper presents this idea as stemming from an approach using presheaves as models of local truth. Finally, I argue that a proper balance between universal and local causation can be assuaged by moving from presheaves to fully-fledged sheaf models. (shrink)

A formal language is positional if it involves a positional connecitve, i.e. a connective of realization to relate formulas to points of a kind, like points of realization or points of relativization. The connective in focus in this paper is the connective “R”, first introduced by Jerzy Łoś. Formulas [Rαφ] involve a singular name α and a formula φ to the effect that φ is satisfied relative to the position designated by α. In weak positional calculi no nested occurences of (...) the connective “R” are allowed. The distribution problem in weak positional logics is actually the problem of distributivity of the connective “R” over classical connectives, viz. the problem of relation between the occurences of classical connectives inside and outside the scope of the positional connective “R”. (shrink)

The connective of realisation associates propositions with names of contexts, at which they are said to be realised. Realisation is usually understood as relativised truth-connective, thus under mo...

I consider the idea of a propositional logic of location based on the following semantic framework, derived from ideas of Prior. We have a collection L of locations and a collection S of statements such that a statement may be evaluated for truth at each location. Typically one and the same statement may be true at one location and false at another. Given this semantic framework we may proceed in two ways: introducing names for locations, predicates for the relations among (...) them and an “at” preposition to express the value of statements at locations; or introduce statement operators which do not name locations but whose truth-conditional effect depends on the truth or falsity of embedded statements at various locations. The latter is akin to Prior’s approach to tense logic. In any logic of location there will be some basic operators which we can define. By ringing the changes on the topology of locations, different logical systems may be generated, and the challenge for the logician is then in each case to find operators, axioms and rules yielding a proof theory adequate to the semantics. The generality of the approach is illustrated with familiar and not so familiar examples from modal, tense and place logic, mathematics, and even the logic of games. To the memory of Ted Dawson, who introduced me to philosophy and the writings of Arthur Prior. (shrink)

Book Reviews: Tomasz Jarmużek and Marcin Tkaczyk, Normalne logiki pozycyjne, Wydawnictwo KUL, Lublin, 2015, 202 pages, ISBN 978-838061-114-6.

O pewnym językowym rozszerzeniu logiki MR: podejście semantyczne i tabelau W artykule przedstawiamy rozszerzenie minimalnej, normalnej logiki pozycyjnej, czyli logiki z operatorem realizacji. Logika pozycyjna to logika filozoficzna, która umożliwia odniesienie zdań do kontekstów, które można rozumieć na wiele sposobów. Wzbogacamy podstawowy język minimalnej logiki pozycyjnej o dodatkowe wyrażenia zbudowane z predykatów i stałych pozycyjnych. Akceptujemy również wyrażenia zbudowane z operatorem realizacji oraz wiele pozycji, takich jak: Dzięki temu zwiększyliśmy wyrazistość minimalnej logiki pozycyjnej. W artykule wskazujemy na wiele przykładów na (...) to, że dzięki tej niewielkiej zmianie mogą powstać złożone teorie oparte na proponowanym rozszerzeniu. Jako teorię dowodu dla naszej logiki zakładamy metody tableau, pokazujące twierdzenia o poprawności i zupełności. Na koniec jednak pokazujemy, że badana tutaj logika jest tylko rozszerzeniem językowym MR: wszystkie twierdzenia o przedłużeniu mają swoje odpowiedniki w czystych twierdzeniach MR. Jednak teorie oparte na proponowanym rozszerzeniu mogą wyrazić znacznie więcej niż teorie oparte na czystej MR. (shrink)