Private Announcements on Topological Spaces

In this work, we present a multi-agent logic of knowledge and change of knowledge interpreted on topological structures. Our dynamics are of the so-called semi-private character where a group G of agents is informed of some piece of information \(\varphi \), while all the other agents observe that group G is informed, but are uncertain whether the information provided is \(\varphi \) or \(\lnot \varphi \). This article follows up on our prior work (van Ditmarsch et al. in Proceedings of the 15th TARK. pp 95-102, 2015) where the dynamics were public events. We provide a complete axiomatization of our logic, and give two detailed examples of situations with agents learning information through semi-private announcements.     

Topological-Frame Products of Modal Logics

The simplest bimodal combination of unimodal logics \(\text {L} _1\) and \(\text {L} _2\) is their fusion, \(\text {L} _1 \otimes \text {L} _2\), axiomatized by the theorems of \(\text {L} _1\) for \(\square _1\) and of \(\text {L} _2\) for \(\square _2\), and the rules of modus ponens, necessitation for \(\square _1\) and for \(\square _2\), and substitution. Shehtman introduced the frame product \(\text {L} _1 \times \text {L} _2\), as the logic of the products of certain Kripke frames: these logics are two-dimensional as well as bimodal. Van Benthem, Bezhanishvili, ten Cate and Sarenac transposed Shehtman’s idea to the topological semantics and introduced the topological product \(\text {L} _1 \times _t \text {L} _2\), as the logic of the products of certain topological spaces. For almost all well-studies logics, we have \(\text {L} _1 \otimes \text {L} _2 \subsetneq \text {L} _1 \times \text {L} _2\), for example, \(\text {S4} \otimes \text {S4} \subsetneq \text {S4} \times \text {S4} \). Van Benthem et al. show, by contrast, that \(\text {S4} \times _t \text {S4} = \text {S4} \otimes \text {S4} \). It is straightforward to define the product of a topological space and a frame: the result is a topologized frame, i.e., a set together with a topology and a binary relation. In this paper, we introduce topological-frame products \(\text {L} _1 \times _ tf \text {L} _2\) of modal logics, providing a complete axiomatization of \(\text {S4} \times _ tf \text {L} \), whenever \(\text {L} \) is a Kripke complete Horn axiomatizable extension of the modal logic D: these extensions include \(\text {T} , \text {S4} \) and \(\text {S5} \), but not \(\text {K} \) or \(\text {K4} \). We leave open the problem of axiomatizing \(\text {S4} \times _ tf \text {K} \), \(\text {S4} \times _ tf \text {K4} \), and other related logics. When \(\text {L} = \text {S4} \), our result confirms a conjecture of van Benthem et al. concerning the logic of products of Alexandrov spaces with arbitrary topological spaces.     

Arithmetical Soundness and Completeness for $$\varvec{\Sigma }_{\varvec{2}}$$ Numerations

We prove that for each recursively axiomatized consistent extension T of Peano Arithmetic and \(n \ge 2\), there exists a \(\Sigma _2\) numeration \(\tau (u)\) of T such that the provability logic of the provability predicate \(\mathsf{Pr}_\tau (x)\) naturally constructed from \(\tau (u)\) is exactly \(\mathsf{K}+ \Box (\Box ^n p \rightarrow p) \rightarrow \Box p\). This settles Sacchetti’s problem affirmatively.     

Praise,blame, and demandingness

Consequentialism has been challenged on the grounds that it is too demanding. I will respond to the problem of demandingness differently from previous accounts. In the first part of the paper, I argue that consequentialism requires us to distinguish the justification of an act \(\varphi\) from the justification of an act \(\psi\), where \(\psi\) is an act of praise or blame. In the second part of the paper, I confront the problem of demandingness. I do not attempt to rule out the objection; instead, I argue that if certain plausible empirical claims about moral motivation are true, we morally ought not to blame people for failing to meet certain very demanding obligations. With this theory, we create a space in consequentialism for intuitions questioning the plausibility of demanding obligations. I conclude the paper by showing that separate justifications for \(\varphi\) and \(\psi\) may also give us a theoretical niche for intuitions about supererogation.     

Two Kinds of Consequential Implication

The first section of the paper establishes the minimal properties of so-called consequential implication and shows that they are satisfied by at least two different operators of decreasing strength (symbolized by \(\rightarrow \) and \(\Rightarrow \)). Only the former has been analyzed in recent literature, so the paper focuses essentially on the latter. Both operators may be axiomatized in systems which are shown to be translatable into standard systems of normal modal logic. The central result of the paper is that the minimal consequential system for \(\Rightarrow \), CI\(\Rightarrow \), is definitionally equivalent to the deontic system KD and is intertranslatable with the minimal consequential system for \(\rightarrow \), CI. The main drawback ot the weaker operator \(\Rightarrow \) is that it lacks unrestricted contraposition, but the final section of the paper argues that \(\Rightarrow \) has some properties which make it a valuable alternative to \(\rightarrow \), turning out especially plausible as a basis for the definition of operators representing synthetic (i.e. context-dependent) conditionals.     

Arithmetical Completeness Theorem for Modal Logic $$\mathsf{}$$

We prove that for any recursively axiomatized consistent extension T of Peano Arithmetic, there exists a \(\Sigma _2\) provability predicate of T whose provability logic is precisely the modal logic \(\mathsf{K}\). For this purpose, we introduce a new bimodal logic \(\mathsf{GLK}\), and prove the Kripke completeness theorem and the uniform arithmetical completeness theorem for \(\mathsf{GLK}\).     

A Routley-Meyer Type Semantics for Relevant Logics Including B<Subscript>r</Subscript> Plus the Disjunctive Syllogism

Routley-Meyer type ternary relational semantics are defined for relevant logics including Routley and Meyer’s basic logic B plus the reductio rule \( \vdash A\rightarrow \lnot A\Rightarrow \vdash \lnot A\) and the disjunctive syllogism. Standard relevant logics such as E and R (plus γ) and Ackermann’s logics of ‘strenge Implikation’ Π and Π^′ are among the logics considered.     

Completeness in Hybrid Type Theory

We show that basic hybridization (adding nominals and @ operators) makes it possible to give straightforward Henkin-style completeness proofs even when the modal logic being hybridized is higher-order. The key ideas are to add nominals as expressions of type t, and to extend to arbitrary types the way we interpret \(@_i\) in propositional and first-order hybrid logic. This means: interpret \(@_i\alpha _a\) , where \(\alpha _a\) is an expression of any type \(a\) , as an expression of type \(a\) that rigidly returns the value that \(\alpha_a\) receives at the i-world. The axiomatization and completeness proofs are generalizations of those found in propositional and first-order hybrid logic, and (as is usual inhybrid logic) we automatically obtain a wide range of completeness results for stronger logics and languages. Our approach is deliberately low-tech. We don’t, for example, make use of Montague’s intensional type s, or Fitting-style intensional models; we build, as simply as we can, hybrid logicover Henkin’s logic.     

Lgbt Catholics: a paradigmatic case of intra-confessional pluralism

ABSTRACT

I will reflect on the reconciliation between “subjective” life and “objective” doctrine experienced by Catholic lgbt couples. Even though their particular experience cannot be considered as universal it can nevertheless constitute a case study for theological reflection. I will propose a theological model for the integration of lgbt Catholics into Christian communities. The case of lgbt Catholics also helps us address the theoretical difficulties of religious pluralism. Their experience of faith is an example of “lived pluralism”. In the lexicon of religious pluralism, this experience is an intra-system or intra-theistic diversity, but it also touches upon the meta-theological issue of the model of reason that is to be applied to every system. I believe that every possible case of pluralism is worth considering if we want to theorize this concept. This may lead us to consider pluralism as a premise from which to start, articulated at different levels.     

Nondeterministic three-valued logic: Isotonic and guarded truth-functions

Nondeterministic programs occurring in recently developed programming languages define nondeterminate partial functions. Formulas (Boolean expressions) of such nondeterministic languages are interpreted by a nonempty subset of {T (“true”), F (“false”), U (“undefined)}. As a semantic basis for the propositional part of a corresponding nondeterministic three-valued logic we study the notion of a truth-function over {T, F, U} which is computable by a nondeterministic evaluation procedure. The main result is that these truth-functions are precisely the functions satisfying four basic properties, called \( \subseteq \) -isotonic, \( \subseteq \) ^?-isotonic, hereditarily guarded, and hereditarily guard-using, and that a function satisfies these properties iff it is explicitly definable (in a certain normal form) from “if..then..else..fi”, binary choice, and constants.     

Reasonable Pluralism,Interculturalism, and Sterba on Question-Beggingness

In From Rationality to Equality, James Sterba (From rationality to equality. New York: Oxford University Press, 2013) argues that the non-moral, and non-controversial, principle of logic, the principle that good arguments do not beg-the-question, provides a rationally conclusive response to egoism. He calls this “the principle of non-question-beggingness” and it is supposed to justify a conception of “Morality as Compromise.” Sterba’s basic idea is that principles of morality provide a non-question-begging compromise between self-interested reasons and other-regarding reasons. I will focus, first, on Sterba’s rejection of the alternative Kantian rationalist justification of morality, and second, I discuss the logical principle of non-question-beggingness and I argue that Sterba is wrong to assume that there is a formal, logical requirement that a rational egoist must provide a non-question-begging defense of egoism. I argue that, like the Kantian, Sterba needs a more substantial conception of practical reason to derive his conclusion. My third focus is the problem of reasonable pluralism and public reason (Rawls in Political liberalism. Columbia University Press, New York, 1996; The law of peoples with the idea of public reason revisited. Harvard University Press, Cambridge, 1999). The Rawlsian principle of public reason is analogous to Sterba’s principle of non-question-beggingness. Sterba recognizes that public policies should respect competing perspectives and that a public conception of justice must be justifiable to all reasonable people. The problem is that that reasonable people disagree about fundamental moral questions. Rawls calls this the fact of reasonable pluralism. I argue that an intercultural conception of justice is necessary to provide a response to reasonable pluralism and a shared basis for public reason.     

The Category of Node-and-Choice Preforms for Extensive-Form Games

It would be useful to have a category of extensive-form games whose isomorphisms specify equivalences between games. Since working with entire games is too large a project for a single paper, I begin here with preforms, where a “preform” is a rooted tree together with choices and information sets. In particular, this paper first defines the category \(\mathbf {Tree}\), whose objects are “functioned trees”, which are specially designed to be incorporated into preforms. I show that \(\mathbf {Tree}\) is isomorphic to the full subcategory of \(\mathbf {Grph}\) whose objects are converging arborescences. Then the paper defines the category \(\mathbf {NCP}\), whose objects are “node-and-choice preforms”, each of which consists of a node set, a choice set, and an operator mapping node-choice pairs to nodes. I characterize the \(\mathbf {NCP}\) isomorphisms, define a forgetful functor from \(\mathbf {NCP}\) to \(\mathbf {Tree}\), and show that \(\mathbf {Tree}\) is equivalent to the full subcategory of \(\mathbf {NCP}\) whose objects are perfect-information preforms. The paper also shows that many game-theoretic entities can be derived from preforms, and that these entities are well-behaved with respect to \(\mathbf {NCP}\) morphisms and isomorphisms.     

Logical Pluralism from a Pragmatic Perspective

This paper presents a new view of logical pluralism. This pluralism takes into account how the logical connectives shift, depending on the context in which they occur. Using the Question-Under-Discussion Framework as formulated by Craige Roberts, I identify the contextual factor that is responsible for this shift. I then provide an account of the meanings of the logical connectives which can accommodate this factor. Finally, I suggest that this new pluralism has a certain Carnapian flavour. Questions about the meanings of the connectives or the best logic outside of a specified context are not legitimate questions.     

Human Psychophysical Functions,an Update: Methods for Identifying their form; Estimating their Parameters; and Evaluating the Effects of Important Predictors

Stevens’ power law for the judgments of sensation has a long history in psychology and is used in many psychophysical investigations of the effects of predictors such as group or condition. Stevens’ formulation \(\varPsi = {aP}^{n}\), where \(\varPsi \) is the psychological judgment, P is the physical intensity, and \(n\) is the power law exponent, is usually tested by plotting log \((\varPsi )\) against log (P). In some, but by no means all, studies, effects on the scale parameter, \(a\), are also investigated. This two-parameter model is simple but known to be flawed, for at least some modalities. Specifically, three-parameter functions that include a threshold parameter produce a better fit for many data sets. In addition, direct non-linear computation of power laws often fit better than regressions of log-transformed variables. However, such potentially flawed methods continue to be used because of assumptions that the approximations are “close enough” as to not to make any difference to the conclusions drawn (or possibly through ignorance the errors in these assumptions). We investigate two modalities in detail: duration and roughness. We show that a three-parameter power law is the best fitting of several plausible models. Comparison between this model and the prevalent two parameter version of Stevens’ power law shows significant differences for the parameter estimates with at least medium effect sizes for duration.     

Public announcement logic with distributed knowledge: expressivity,completeness and complexity

While dynamic epistemic logics with common knowledge have been extensively studied, dynamic epistemic logics with distributed knowledge have so far received far less attention. In this paper we study extensions of public announcement logic (\(\mathcal{PAL }\)) with distributed knowledge, in particular their expressivity, axiomatisations and complexity. \(\mathcal{PAL }\) extended only with distributed knowledge is not more expressive than standard epistemic logic with distributed knowledge. Our focus is therefore on \(\mathcal{PACD }\), the result of adding both common and distributed knowledge to \(\mathcal{PAL }\), which is more expressive than each of its component logics. We introduce an axiomatisation of \(\mathcal{PACD }\), which is not surprising: it is the combination of well-known axioms. The completeness proof, however, is not trivial, and requires novel combinations and extensions of techniques for dealing with \(S5\) knowledge, distributed knowledge, common knowledge and public announcements at the same time. We furthermore show that \(\mathcal{PACD }\) is decidable, more precisely that it is \(\textsc {exptime}\)-complete. This result also carries over to \(\mathcal{S 5\mathcal CD }\) with common and distributed knowledge operators for all coalitions (and not only the grand coalition). Finally, we propose a notion of a trans-bisimulation to generalise certain results and give deeper insight into the proofs.     

Duality Theory and Skeleta for Semisimple MV-Algebras

We start from Marra–Spada duality between semisimple MV-algebras and Tychonoff spaces, and we consider the particular cases when the \(\omega \)-skeleta of the MV-algebras are restricted in some way. In particular we consider antiskeletal MV-algebras, that is, the ones whose \(\omega \)-skeleton is trivial.     

Axiomatizing Jaśkowski’s Discussive Logic $$\mathbf {D_2}$$

We outline the rather complicated history of attempts at axiomatizing Ja?kowski’s discussive logic \(\mathbf {D_2}\) and show that some clarity can be had by paying close attention to the language we work with. We then examine the problem of axiomatizing \(\mathbf {D_2}\) in languages involving discussive conjunctions. Specifically, we show that recent attempts by Ciuciura are mistaken. Finally, we present an axiomatization of \(\mathbf {D_2}\) in the language Ja?kowski suggested in his second paper on discussive logic, by following a remark of da Costa and Dubikajtis. We also deal with an interesting variant of \(\mathbf {D_2}\), introduced by Ciuciura, in which negation is also taken to be discussive.     

Sequent Calculi for Semi-De Morgan and De Morgan Algebras

A contraction-free and cut-free sequent calculus \(\mathsf {G3SDM}\) for semi-De Morgan algebras, and a structural-rule-free and single-succedent sequent calculus \(\mathsf {G3DM}\) for De Morgan algebras are developed. The cut rule is admissible in both sequent calculi. Both calculi enjoy the decidability and Craig interpolation. The sequent calculi are applied to prove some embedding theorems: \(\mathsf {G3DM}\) is embedded into \(\mathsf {G3SDM}\) via Gödel–Gentzen translation. \(\mathsf {G3DM}\) is embedded into a sequent calculus for classical propositional logic. \(\mathsf {G3SDM}\) is embedded into the sequent calculus \(\mathsf {G3ip}\) for intuitionistic propositional logic.     

The essential invisibility of trauma and the need for repetition commentary on Shabad's “resentment,indignation, entitlement”;

This paper assesses the implications of Grünbaum's critique of Freud's “science”; for a discussion of the relation between theory and practice in psychoanalytically oriented psychotherapy. Guided by the work of the French sociologist, Bourdieu, it places Grünbaum's argument within a logic of intellectualism—a framework that tends to instrumentalize reason and romanticize practice, delineating the well‐known territories of objectivism and subjectivism. Grünbaum's arguments within this logic are taken to be rhetorical maneuvers—such as valorizing the tally argument and then debunking it—aimed at rejuvenating an objectivistic approach to theory and practice. Grünbaum is successful insofar as much of the debate generated by his views accepts the terms of his intellectualist bias. It is suggested, however, that these are terms that have long been suspect; that, indeed, it was Freud who helped bring them into question; and that there is a broader framework of discourse that relativizes intellectualism within a dialectical opposition to “participationism.”; A form of rationality founded in a nonconceptual knowledge of practice has begun to emerge within this more inclusive discourse under such rubrics as “social constructivist”; and “relational”; approaches to psychotherapy. It is argued that within the therapy situation a kind of “practical reason”; can mitigate the controlling, instrumental authority of intellectualism as well as the collusive, sentimental servility of participationism.

[T]he theoretician's claim to an absolute viewpoint, the “perspec‐tiveless view of all perspectives”; as Leibnitz would have put it, contains the claim to a power, founded in reason, over particular individuals, who are condemned to error by the partisan partiality of their individual viewpoints [Bourdieu, 1990, pp. 28–29]1 ^lThe work of sociologist Pierre Bourdieu (1977, 1990; Bourdieu and Wacquant, 1992) focuses on a scientific study of human interaction that is cognizant of the pitfalls of the conflicting poles within intellectualism of “objectivism”; and “subjectivism"—both of which are rejected. and redefined relative to the recognition of a distinct “logic of practice.”; I hope that the perceived significance of this work to the understanding of psychoanalytic practice will justify my extensive use of quotations.      

Truth,Partial Logic and Infinitary Proof Systems

In this paper we apply proof theoretic methods used for classical systems in order to obtain upper bounds for systems in partial logic. We focus on a truth predicate interpreted in a Kripke style way via strong Kleene; whereas the aim is to connect harmoniously the partial version of Kripke–Feferman with its intended semantics. The method we apply is based on infinitary proof systems containing an \(\omega \)-rule.