This book provides a detailed exposition of one of the most practical and popular methods of proving theorems in logic, called Natural Deduction. It is presented both historically and systematically. Also some combinations with other known proof methods are explored. The initial part of the book deals with Classical Logic, whereas the rest is concerned with systems for several forms of Modal Logics, one of the most important branches of modern logic, which has wide applicability.

In the tradition of quantified modal logic, it was assumed that significantly different linguistic systems underlie reference to individuals, to times and to ‘possible worlds’. Various results from recent research in formal semantics suggest that this is not so, and that there is in fact apervasive symmetrybetween the linguistic means with which we refer to these three domains. Reference to individuals, times and worlds is uniformly effected through generalized quantifiers, definite descriptions, and pronouns, and in each domain grammatical features situate (...) the reference of terms as near, far or ‘further’ from the actual or from a reported speech act. We outline various directions in which a program ofontological symmetrycould be developed, and we offer in theAppendixa symmetric fragment developed in a logic that can be seen as a compromise between an extensional and an intensional system. (shrink)

In the tradition of quantified modal logic, it was assumed that significantly different linguistic systems underlie reference to individuals, to times and to 'possible worlds'. Various results from recent research in formal semantics suggest that this is not so, and that there is in fact a pervasive symmetry between the linguistic means with which we refer to these three domains. Reference to individuals, times and worlds is uniformly effected through generalized quantifiers, definite descriptions, and pronouns, and in each domain grammatical (...) features situate the reference of terms as near, far or 'further' from the actual or from a reported speech act. We outline various directions in which a program of ontological symmetry could be developed, and we offer in the Appendix a symmetric fragment developed in a logic that can be seen as a compromise between an extensional and an intensional system. (shrink)

Stalnaker ( 1978 ) made two seminal claims about presuppositions. The most influential one was that presupposition projection is computed by a pragmatic mechanism based on a notion of ‘local context’ . Due to conceptual and technical difficulties, however, the latter notion was reinterpreted in purely semantic terms within ‘dynamic semantics’ (Heim 1983 ). The second claim was that some instances of presupposition generation should also be explained in pragmatic terms . But despite various attempts, the definition of a precise (...) ‘triggering algorithm’ has remained somewhat elusive. We discuss possible extensions of both claims. First, we offer a reconstruction of ‘local contexts’ which circumvents some of the difficulties faced by Stalnaker’s original analysis. We preserve the idea that local contexts are computed by a pragmatic mechanism that aggregates the information that follows from an incomplete sentence given the global context; but we crucially rely on a modified notion of entailment (‘R-entailment’), whose plausibility should be assessed on independent grounds. Second, we speculate that local contexts might prove necessary (though by no means sufficient) to understand how some presuppositions are triggered. In a nutshell, we suggest that a presupposition is triggered when the semantic contribution of an expression to its local context is in some sense ‘heterogeneous’. Without giving an analysis of the latter notion, we note that this architecture implies that presuppositions should be triggered on the basis of the meaning that an expression has relative to its local context (what we call its ‘local meaning’); we sketch some possible consequences of this analysis. (shrink)

The purpose of this paper is to argue that the hybrid formalism fits naturally in the context of David Lewis’s counterfactual logic and that its introduction into this framework is desirable. This hybridization enables us to regard the inference “The pig is Mary; Mary is pregnant; therefore the pig is pregnant” as a process of updating local information (which depends on the given situation) by using global information (independent of the situation). Our hybridization also has the following technical advantages: (i) (...) it preserves the completeness and decidability of Lewis’s logic; (ii) it allows us to characterize the Limit Assumption as a proof-rule with some side-conditions; and (iii) it enables us to establish a general Kripke completeness result by using the proof-rule corresponding to the Limit Assumption. Keywords Counterfactual logic - David Lewis - Contextually definite description - Hybrid logic - Arthur Prior - The limit assumption - Strong completeness - Decidability - Bisimulation - Pure completeness. (shrink)

The article reviews some analyses of temporal language in logical approaches to natural language semantics. It considers some asymmetries between past and future, manifested in language, which motivate the “standard view” of the non-reversibility of time and the persistence of the past. It concludes with a puzzle about the changing past which challenges the standard view.

I will show how a metaphysical problem of Arthur Prior’s can be solved by a logical tool he developed himself, but did not put to any foundational use: metric logic. The broader context is given by the key question about the metaphysics of time: Is time tenseless, i.e., is time just a structure of instants; or is time tensed, because some facts are irreducibly tensed? I take sides with Prior and the tensed theory. Like him, I therefore I have to (...) deal with a more specific metaphysical question: How can the instants of tenseless time be reduced to tensed facts? This is the point where, on the technical level, hybrid logic and metric logic come in. For present purposes, both can be seen as species of tense logic; and both are creations of Prior. In his argument for the tensed theory of time, Prior used hybrid tense logic to reduce instants. But, as he himself pointed out, this reduction runs into deep problems, because it immediately generalizes to other categories, for example and most importantly to persons. My main aim is to show that metric logic does not run into similar difficulties: It will help the tensed theory reduce instants, but it leaves persons untouched. I will also give reasons for preferring a metric to a hybrid logic of time that are independent of the metaphysical issue of reduction, but concern temporal reasoning, natural language semantics, and the epistemic side of time-keeping. (shrink)

In the pair of articles of which this is the first, I shall present a set of problems and philosophical proposals that have in recent years been associated with the term “relativism”. All these problems and proposals concern the question of how we should represent thought and speech about certain topics. The main issue here is whether we should model such mental states or linguistic acts as involving representational contents that are absolutely correct or incorrect, or whether, alternatively, their correctness (...) should be thought of as varying with some (more or less surprising) factor. In this, first, article, I shall discuss the general issue of relativism about representational content. I shall claim that there are legitimate ways of attributing contents that are absolute truth-bearers, and there are also equally legitimate ways of attributing relativistic representational contents. In the companion piece “Relativism 2: Semantic Content”, I look in more detail at the more specific question whether semantic contents (i.e. the contents assigned to linguistic utterances in the semantics of natural language) should be construed in an absolutist or a relativist way. (shrink)

This is an extended version of the lectures given during the 12-thConference on Applications of Logic in Philosophy and in the Foundationsof Mathematics in Szklarska Poręba. It contains a surveyof modal hybrid logic, one of the branches of contemporary modal logic. Inthe first part a variety of hybrid languages and logics is presented with adiscussion of expressivity matters. The second part is devoted to thoroughexposition of proof methods for hybrid logics. The main point is to showthat application of hybrid logics (...) may remarkably improve the situation inmodal proof theory. (shrink)

Although it receives less attention, (Lewis in Noûs 13:455–476, 1979. https://doi.org/10.2307/2215339) admitted that the branching-time(-like) model fits a wide range of counterfactuals, including (Nix) ‘If Nixon had pressed the button, there would have been a nuclear war’, which was raised by (Fine in Mind 84:451–458, 1975). However, Lewis then claimed that similarity analysis is more general than temporality analysis. In this paper, we do not scrutinise his claim. Instead, we re-analyse (Nix) not only model-theoretically but also proof-theoretically from the ‘meaning-as-use’ (...) and ‘inferentialist’ points of view. Then, we re-formalise (Nix) in a natural extension of hybrid tense logic, which we refer to as hybrid tense logic for temporal conditionals (HTL$$_{TC}$$ TC ). Consequently, we find that not only among counterfactuals, but also among indicatives, there is a wide range of conditionals whose formalisation in HTL$$_{TC}$$ TC is appropriate. We refer to these conditionals as temporal conditionals. This suggests a new logical generality that temporality analysis has but similarity analysis does not, from which emerges a new logical perspective on conditionals in general: temporal ones and others. (shrink)

At the centre of Arthur Prior’s ‘Thank goodness’ argument for the A-theory of time is a particular form of relief. Time must objectively pass, Prior argues, or else the relief felt when a painful experience has ended is not intelligible. In this paper, I offer a detailed analysis of the type of relief at issue in this argument, which I call temporal relief, and distinguish it from another form of relief, which I refer to as counterfactual relief. I also argue (...) that existing discussions of the ‘Thank goodness’ argument—including Prior’s own—fail to give a satisfactory account of temporal relief, and that it needs to be seen as an emotion linked to the ability to engage in fairly sophisticated forms of planning. I also suggest that this has an impact on Prior’s claim that the idea of points in time plays no fundamental role in the semantic analysis of tenses. (shrink)

In this paper we argue that Prior and Reichenbach are best viewed as allies, not antagonists. We do so by combining the central insights of Prior and Reichenbach in the framework of hybrid tense logic. This overcomes a well-known defect of Reichenbach’s tense schema, namely that it gives multiple representations to sentences in the future perfect and the future-in-the-past. It also makes it easy to define an iterative schema for tense that allows for multiple points of reference, a possibility noted (...) by Prior and demanded by Comrie, and we sketch how this schema can be generalized to a shift-and-restrict pattern in which special propositional symbols act as restrictors on the range of tense operators. (shrink)

Hybrid languages have both modal and first-order characteristics: a Kripke semantics, and explicit variable binding apparatus. This paper motivates the development of hybrid languages, sketches their history, and examines the expressive power of three hybrid binders. We show that all three binders give rise to languages strictly weaker than the corresponding first-order language, that full first-order expressivity can be gained by adding the universal modality, and that all three binders can force the existence of infinite models and have undecidable satisfiability (...) problems. (shrink)

Contemporary hybrid logic is based on the idea of using formulas as terms, an idea invented and explored by Arthur Prior in the mid-1960s. But Prior’s own work on hybrid logic remains largely undiscussed. This is unfortunate, since hybridisation played a role that was both central to and problematic for his philosophical views on tense. In this paper I introduce hybrid logic from a contemporary perspective, and then examine the role it played in Prior’s work.

Este artigo canta uma canção — uma canção criada ao unir o trabalho de quatro grandes nomes na história da lógica: Hans Reichenbach, Arthur Prior, Richard Montague, e Leon Henkin. Embora a obra dos primeiros três desses autores tenha sido previamente combinada, acrescentar as ideias de Leon Henkin é o acréscimo requerido para fazer com que essa combinação funcione no nível lógico. Mas o presente trabalho não se concentra nas tecnicalidades subjacentes (que podem ser encontradas em Areces, Blackburn, Huertas, e (...) Manzano [no prelo]), e sim nos instrumentos subjacentes e no modo como trabalham em conjunto. Esperamos que o leitor fique tentado a cantar junto. DOI:10.5007/1808-1711.2011v15n2p225. (shrink)

This paper outlines a truth-conditional view of logical form, that is, a view according to which logical form is essentially a matter of truth-conditions. The main motivation for the view is a fact that seems crucial to logic. As _§_1 suggests, fundamental logical relations such as entailment or contradiction can formally be explained only if truth-conditions are formally represented.§2 spells out the view. _§_3 dwells on its anity with a conception of logical form that has been defended in the past. (...) _§§_4-6 draw attention to its impact on three major issues that concern, respectively, the extension of the domain of formal explanation, the semantics of tensed discourse, and the analysis of quantication. (shrink)

Can we solve the problem of the essential indexical, and account for de se belief, by appealing to 'relativized propositions' (functions from rich indices to truth-values)? According to John Perry, we cannot. This paper offers a detailed examination and a critique of Perry's argument.

The Linda paradox is a key topic in current debates on the rationality of human reasoning and its limitations. We present a novel analysis of this paradox, based on the notion of verisimilitude as studied in the philosophy of science. The comparison with an alternative analysis based on probabilistic confirmation suggests how to overcome some problems of our account by introducing an adequately defined notion of verisimilitudinarian confirmation.

Nuestro principal objetivo en este trabajo es el de analizar si es posible construir sistemas lógicos temporales-epistémicos lo suficientemente satisfactorios. Sin embargo, las principales dificultades para lograr este propósito provienen del hecho de tener que combinar una perspectiva temporal absoluta con una perspectiva epistémica relativa a cada agente; es decir, por un lado, los instantes de tiempo vienen determinados desde el punto de vista de un observador situado fuera del mundo, y, por otro lado, las alternativas epistémicas de cada agente (...) son relativas a dicho agente. Pensamos que algunas de estas dificultades podrían ser superadas con la ayuda de las lógicas híbridas, puesto que este tipo de lógicas simplifica la combinación de sistemas temporales y epistémicos, y así podemos evitar tener que construir modelos excesivamente complicados. Our main goal in this paper is to analyse if it is possible to build some suitable Temporal-Epistemic Systems. However, the main difficulties in order to aim this goal come from the fact of having to combine an absolute temporal perspective with a relative epistemic perspective; that is, on one hand, temporal points are determined from the point of view of an observer placed outside the world, and, on the other hand, the epistemic alternatives of each agent are relative to that agent. We think that some of these difficulties could be solved with the help of hybrid logics, because this kind of logics simplifies the combination of temporal and epistemic systems, and so we can avoid building highly complicated models. (shrink)