We present a complete, decidable logic for reasoning about a notion of completely trustworthy evidence and its relations to justifiable belief and knowledge, as well as to their explicit justifications. This logic makes use of a number of evidence-related notions such as availability, admissibility, and “goodness” of a piece of evidence, and is based on an innovative modification of the Fitting semantics for Artemovʼs Justification Logic designed to preempt Gettier-type counterexamples. We combine this with ideas from belief revision and awareness (...) logics to provide an account for explicitly justified knowledge based on conclusive evidence that addresses the problem of omniscience. (shrink)

We address the old question whether a logical understanding of Quantum Mechanics requires abandoning some of the principles of classical logic. Against Putnam and others (Among whom we may count or not E. W. Beth, depending on how we interpret some of his statements), our answer is a clear "no". Philosophically, our argument is based on combining a formal semantic approach, in the spirit of E. W. Beth's proposal of applying Tarski's semantical methods to the analysis of physical theories, with (...) an empirical-experimental approach to Logic, as advocated by both Beth and Putnam, but understood by us in the view of the operationalrealistic tradition of Jauch and Piron, i. e. as an investigation of "the logic of yes-no experiments" (or "questions"). Technically, we use the recently-developed setting of Quantum Dynamic Logic (Baltag and Smets 2005, 2008) to make explicit the operational meaning of quantum-mechanical concepts in our formal semantics. Based on our recent results (Baltag and Smets 2005), we show that the correct interpretation of quantum-logical connectives is dynamical, rather than purely propositional. We conclude that there is no contradiction between classical logic and (our dynamic reinterpretation of) quantum logic. Moreover, we argue that the Dynamic-Logical perspective leads to a better and deeper understanding of the "non-classicality" of quantum behavior than any perspective based on static Propositional Logic. (shrink)

This paper presents a simple decidable logic of functional dependence LFD, based on an extension of classical propositional logic with dependence atoms plus dependence quantifiers treated as modalities, within the setting of generalized assignment semantics for first order logic. The expressive strength, complete proof calculus and meta-properties of LFD are explored. Various language extensions are presented as well, up to undecidable modal-style logics for independence and dynamic logics of changing dependence models. Finally, more concrete settings for dependence are discussed: continuous (...) dependence in topological models, linear dependence in vector spaces, and temporal dependence in dynamical systems and games. (shrink)

Stalnaker, 169–199 2006) introduced a combined epistemic-doxastic logic that can formally express a strong concept of belief, a concept of belief as ‘subjective certainty’. In this paper, we provide a topological semantics for belief, in particular, for Stalnaker’s notion of belief defined as ‘epistemic possibility of knowledge’, in terms of the closure of the interior operator on extremally disconnected spaces. This semantics extends the standard topological interpretation of knowledge with a new topological semantics for belief. We prove that the belief (...) logic KD45 is sound and complete with respect to the class of extremally disconnected spaces and we compare our approach to a different topological setting in which belief is interpreted in terms of the derived set operator. We also study belief revision as well as belief dynamics by providing a topological semantics for conditional belief and belief update modalities, respectively. Our setting based on extremally disconnected spaces, however, encounters problems when extended with dynamic updates. We then propose a solution consisting in interpreting belief in a similar way based on hereditarily extremally disconnected spaces, and axiomatize the belief logic of hereditarily extremally disconnected spaces. Finally, we provide a complete axiomatization of the logic of conditional belief and knowledge, as well as a complete axiomatization of the corresponding dynamic logic. (shrink)

Ancien élève de Heidegger, Alexandru Dragomir (1916-2002) est une figure atypique de la philosophie. Abandonnant l'idée d'une carrière universitaire après la Seconde guerre mondiale, il navigua d'un métier à un autre, refusant catégoriquement d'être publié de son vivant. Il laisse aujourd'hui à nos curiosités ses Banalités métaphysiques, extraites des cahiers dans lesquels il griffonait des notes à sa propre intention. Banalités métaphysiques est la première publication de ce philosophe hors norme, tiré malgré lui de son retrait volontaire.

We present a logical calculus for reasoning about information flow in quantum programs. In particular we introduce a dynamic logic that is capable of dealing with quantum measurements, unitary evolutions and entanglements in compound quantum systems. We give a syntax and a relational semantics in which we abstract away from phases and probabilities. We present a sound proof system for this logic, and we show how to characterize by logical means various forms of entanglement (e.g. the Bell states) and various (...) linear operators. As an example we sketch an analysis of the teleportation protocol. (shrink)

We investigate the process of truth-seeking by iterated belief revision with higher-level doxastic information . We elaborate further on the main results in Baltag and Smets (Proceedings of TARK, 2009a , Proceedings of WOLLIC’09 LNAI 5514, 2009b ), applying them to the issue of convergence to truth . We study the conditions under which the belief revision induced by a series of truthful iterated upgrades eventually stabilizes on true beliefs. We give two different conditions ensuring that beliefs converge to “full” (...) (complete) truth , as well as a condition ensuring only that they converge to true (but not necessarily complete) beliefs. (shrink)

In this paper, I propose a new way to distinguish between indexicals, like “I” and “today”, and demonstratives, like “she” and “this”. The main test case is the second person singular pronoun “you”. The tradition would generally count it as a demonstrative, because the speaker’s intentions play a role in providing it with a semantic value. I present cross-linguistic data and explanations offered of the data in typology and semantics to show that “you” belongs on the indexical side, and argue (...) that they can be generalized to a novel criterion for distinguishing between indexicals and demonstratives. The central theoretical claim is that the semantic values of indexicals are objects which play certain utterance-related roles, which are fixed independently of the words being used in the utterance. For instance, the speaker plays the speaker role whether or not she uses the word “I”, and the addressee plays that role whether or not the speaker uses the word “you”. Demonstratives, on the other hand, pick out objects that play no such role, and are instead helped by the speaker’s word-specific intentions. (shrink)

We construct logical languages which allow one to represent a variety of possible types of changes affecting the information states of agents in a multi-agent setting. We formalize these changes by defining a notion of epistemic program. The languages are two-sorted sets that contain not only sentences but also actions or programs. This is as in dynamic logic, and indeed our languages are not significantly more complicated than dynamic logics. But the semantics is more complicated. In general, the semantics of (...) an epistemic program is what we call aprogram model. This is a Kripke model of ‘actions’,representing the agents' uncertainty about the current action in a similar way that Kripke models of ‘states’ are commonly used in epistemic logic to represent the agents' uncertainty about the current state of the system. Program models induce changes affecting agents' information, which we represent as changes of the state model, called epistemic updates. Formally, an update consists of two operations: the first is called the update map, and it takes every state model to another state model, called the updated model; the second gives, for each input state model, a transition relation between the states of that model and the states of the updated model. Each variety of epistemic actions, such as public announcements or completely private announcements to groups, gives what we call an action signature, and then each family of action signatures gives a logical language. The construction of these languages is the main topic of this paper. We also mention the systems that capture the valid sentences of our logics. But we defer to a separate paper the completeness proof. (shrink)

Since Kaplan : 81–98, 1979) first provided a logic for context-sensitive expressions, it has been thought that the only way to construct a logic for indexicals is to restrict it to arguments which take place in a single context— that is, instantaneous arguments, uttered by a single speaker, in a single place, etc. In this paper, I propose a logic which does away with these restrictions, and thus places arguments where they belong, in real world conversations. The central innovation is (...) that validity depends not just on the sentences in the argument, but also on certain abstract relations between contexts. This enrichment of the notion of logical form leads to some seemingly counter-intuitive results: a sequence of sentences may make up a valid argument in one sequence of contexts, and an invalid one in another such sequence. I argue that this is an unavoidable result of context sensitivity in general, and of the nature of indexicals in particular, and that reflection on such examples will lead us to a better understanding of the idea of applying logic to context sensitive expressions, and thus to natural language in general. (shrink)

We propose a new model for forming and revising beliefs about unknown probabilities. To go beyond what is known with certainty and represent the agent’s beliefs about probability, we consider a plausibility map, associating to each possible distribution a plausibility ranking. Beliefs are defined as in Belief Revision Theory, in terms of truth in the most plausible worlds. We consider two forms of conditioning or belief update, corresponding to the acquisition of two types of information: learning observable evidence obtained by (...) repeated sampling from the unknown distribution; and learning higher-order information about the distribution. The first changes only the plausibility map, but leaves the given set of possible distributions essentially unchanged; the second rules out some distributions, thus shrinking the set of possibilities, without changing their plausibility ordering.. We look at stability of beliefs under either of these types of learning, defining two related notions, as well as a measure of the verisimilitude of a given plausibility model. We prove a number of convergence results, showing how our agent’s beliefs track the true probability after repeated sampling, and how she eventually gains in a sense knowledge of that true probability. Finally, we sketch the contours of a dynamic doxastic logic for statistical learning. (shrink)

In this article we aim to reduce the force of the expensive tastes objection to equality of welfare by constructing a pluralist welfare egalitarian theory which is not defeated by it. In the first part, we argue that Cohen’s condition of responsibility-sensitiveness is not able to provide a satisfactory rebuttal of the expensive tastes objection for at least a class of theories of justice, namely those that adhere to a methodologically fact-sensitive view. In the second part, we explore the possibility (...) of constructing a welfare egalitarian theory that gives weight to both equality and efficiency. We propose two alternatives, which integrate a utilitarian constraint and a Weak Pareto constraint on equality and show that both theories consistently differentiate between compensable and non-compensable expensive tastes, but should ultimately be rejected because of other unattractive implications. Finally, we develop a fairness-constrained theory of welfare egalitarianism and suggest that it can distinguish between compensable and non-compensable expensive tastes in both a conceptually consistent and a morally plausible manner, without generating decisive additional objections. (shrink)

The classical rule of Repetition says that if you take any sentence as a premise, and repeat it as a conclusion, you have a valid argument. It's a very basic rule of logic, and many other rules depend on the guarantee that repeating a sentence, or really, any expression, guarantees sameness of referent, or semantic value. However, Repetition fails for token-reflexive expressions. In this paper, I offer three ways that one might replace Repetition, and still keep an interesting notion of (...) validity. Each is a fine way to go for certain purposes, but I argue that one in particular is to be preferred by the semanticist who thinks that there are token-reflexive expressions in natural languages. (shrink)

In this article I aim to offer a first critical assessment of the most prominent arguments in favour of restricting the voting rights of senior citizens. The first argument discussed, most thoroughly articulated by van Parijs, maintains that intergenerational justice would be improved under schemes which restrict the voting rights of senior citizens, thereby diminishing their overall electoral weight. The second argument, reconstructed from Lau's defence of child enfranchisement, maintains that the cognitive decline associated with the process of aging should (...) lead us to treat children and senior citizens identically in respect to electoral rights; thus, if we agree that children should not have the right to vote, consistency dictates that senior citizens should be disenfranchised as well. I respond to these arguments with several objections, arguing that the former relies on a number of faulty empirical premises and has deeply unattractive implications for enfranchisement once consistently applied, and that the latter fails to make empirically salient distinctions between children and senior citizens when it comes to the political domain. (shrink)

The present article represents an attempt to argue in the favor of the thesis that, in the First Meditation, in the fragment where the problem of madness is spoken of, Descartes’ view aims to exclude the possibility that the knowing subject, the Cogito, could be insane, and not only to avoid the problem of madness because of various reasons or to replace the madness-example with a dreaming-example. In other words, this research aims to expose and to argue for Michel Foucault’s (...) point of view regarding the Cartesian problem of madness, and also to argue against Jacques Derrida’s view on the same issue. More broadly speaking, beyond the highlight of a possible different approach to Descartes’ text or the analysis of the Derrida-Foucault controversy, the main aim of this article is to emphasize a problem maybe less discussed of the act of knowing: beyond the proper usage of a wrong method, the misusage of a correct method or the poor practice of some spiritual exercises, the errors in the act of knowledge could as well follow from a deficiency in the knowing subject itself. (shrink)

In this article I aim to provide the first normative discussion of barter voting markets, namely markets which allow the trading of votes on issues/elections for votes on other issues/elections. The article is framed within the wider literature on the legal permissibility of vote buying, with a particular focus on the recent debate between Christopher Freiman and James Stacey Taylor. I argue that while Taylor's objections successfully defeat Freiman's case in favour of standard voting markets, they are unable to also (...) defeat the type of voting markets outlined here. Furthermore, I argue that there are at least two plausible prima facie reasons in favour of barter voting markets, grounded in their capacity to contribute to the alleviation of injustice for systematically disadvantaged socio‐economic groups and to their capacity to reduce one form of bad voting, i.e. voting from ignorance. (shrink)

In this annotated critical edition of Aristotle’s Metaphysics Lambda Stefan Alexandru draws upon many hitherto unexplored sources of the direct and indirect tradition, inter alia upon an independent Greek manuscript he has discovered in the Vatican Library.

This book is a puzzle inspired by the fresh, colourful rolling landscapes of Gruyère, where a wise man once asked me, “Does the castle over the mountain exist if nobody sees it?” “Yes,” I answered, “as we have all learned that what we know is not always what reality is.” We agree that theoretical ‘knowledge’ needs practical confirmation within reality. But what if we find reality in its very essence, intelligence or knowledge, as Neoplatonists did? The unknown would become unreal, (...) void. When investigating the existence of a cause of all things—the One origin—Damascius, the last head of Plato’s Academy (which closed in 529), writes about its complete ineffability: its lack of position and absence in relation to reality, whether intelligible or not. This void is further reversed into a theoretical framework that defines causality as a global, systemic condition of the world as a whole.About the author: Alexandru Pelin is a philosopher and cyber security professional. (shrink)

Synonymy, at its most basic, is sameness of meaning. A token-reflexive expression is an expression whose meaning assigns a referent to its tokens by relating each particular token of that particular expression to its referent. In doing so, the formulation of its meaning mentions the particular expression whose meaning it is. This seems to entail that no two token-reflexive expressions are synonymous, which would constitute a strong objection against token-reflexive semantics. In this paper, I propose and defend a notion of (...) synonymy for token-reflexive expressions that allows such expressions to be synonymous, while being a fairly conservative extension of the customary notion of synonymy. (shrink)

This paper discusses the reception of Frankfurt School critical theory in Communist Romania. After some opening remarks concerning the relevance of this topic, Section 2 sketches the evolving political and historical contexts that circumscribed this philosophical reception. The content and configuration of the Romanian reception of critical theory is then discussed in a double sequence: first (Section 3), by surveying and analysing the main clusters of arguments developed in these texts, which are filtered and classified into four categories: a) general (...) considerations and strategic approach to critical theory; b) positive assessments; c) philosophical critiques; d) politico-practical critiques. Then, Section 4 attempts to delineate the divergent paths adumbrated in this field of critical reception, which it illustrates through the specific authorial trajectories of the main Romanian interpreters (Tertulian, Marga and Tismăneanu). Finally, the concluding remarks are devoted to some brief comparative and historical considerations on the meaning, value and amplitude of this critical reception. (shrink)

In this paper we aim to examine a novel view on distributive justice, i.e. limitarianism, which claims that it is morally impermissible to be rich. Our main goal is to assess the two arguments provided by Ingrid Robeyns in favour of limitarianism, namely the democratic argument and the argument from unmet urgent needs and the two distinct limitarian views which these arguments give rise to. We claim that strong limitarianism, which is supported by the democratic argument, should be rejected as (...) it fails to fully instantiate the value of political equality, while having some other unattractive implications as well. By contrast, we argue that weak limitarianism, which is supported by the argument from unmet urgent needs, should be endorsed, albeit in a qualified version which also takes responsibility constraints into consideration. (shrink)

We take a logical approach to threshold models, used to study the diffusion of opinions, new technologies, infections, or behaviors in social networks. Threshold models consist of a network graph of agents connected by a social relationship and a threshold value which regulates the diffusion process. Agents adopt a new behavior/product/opinion when the proportion of their neighbors who have already adopted it meets the threshold. Under this diffusion policy, threshold models develop dynamically towards a guaranteed fixed point. We construct a (...) minimal dynamic propositional logic to describe the threshold dynamics and show that the logic is sound and complete. We then extend this framework with an epistemic dimension and investigate how information about more distant neighbors’ behavior allows agents to anticipate changes in behavior of their closer neighbors. Overall, our logical formalism captures the interplay between the epistemic and social dimensions in social networks. (shrink)

In this paper, we investigate the social herding phenomenon known as informational cascades, in which sequential inter-agent communication might lead to epistemic failures at group level, despite availability of information that should be sufficient to track the truth. We model an example of a cascade, and check the correctness of the individual reasoning of each agent involved, using two alternative logical settings: an existing probabilistic dynamic epistemic logic, and our own novel logic for counting evidence. Based on this analysis, we (...) conclude that cascades are not only likely to occur but are sometimes unavoidable by "rational" means: in some situations, the group’s inability to track the truth is the direct consequence of each agent’s rational attempt at individual truth-tracking. Moreover, our analysis shows that this is even so when rationality includes unbounded higher-order reasoning powers, as well as when it includes simpler, non-Bayesian forms of heuristic reasoning. (shrink)

The goal of this paper is to present a collection of properties of the set of atoms and the set of finite injective tuples of atoms, as well as of the powersets of atoms in the framework of finitely supported structures. Some properties of atoms are obtained by translating classical Zermelo–Fraenkel results into the new framework, but several important properties are specific to finitely supported structures.

The article conveys the portrait of a man for whom understanding was a matter of the highest spiritual intimacy, a man who continuously disregarded his possible engagement in the public life as a philosopher, finally a man whom we find, in the twilight of his life, concerned with the intricate tension between the “muteness” of philosophy (as being able “only” to double life by means of rational discourse) and religion. Alexandru Dragomir’s portrait is portrayed in comparison to another important (...) Romanian philosopher, Constantin Noica. The comparison is not accidental, since they both come to represent two paradigmatic ways of making philosophy: traditional ontology (centered around Descartes – Kant – Hegel) vs. modern phenomenology (centered around Husserl – Heidegger). (shrink)

We study the learning power of iterated belief revision methods. Successful learning is understood as convergence to correct, i.e., true, beliefs. We focus on the issue of universality: whether or not a particular belief revision method is able to learn everything that in principle is learnable. We provide a general framework for interpreting belief revision policies as learning methods. We focus on three popular cases: conditioning, lexicographic revision, and minimal revision. Our main result is that conditioning and lexicographic revision can (...) drive a universal learning mechanism, provided that the observations include only and all true data, and provided that a non-standard, i.e., non-well-founded prior plausibility relation is allowed. We show that a standard, i.e., well-founded belief revision setting is in general too narrow to guarantee universality of any learning method based on belief revision. We also show that minimal revision is not universal. Finally, we consider situations in which observational errors may occur. Given a fairness condition, which says that only finitely many errors occur, and that every error is eventually corrected, we show that lexicographic revision is still universal in this setting, while the other two methods are not. (shrink)

We present a semantic analysis of the Ramsey test, pointing out its deep underlying flaw: the tension between the “static” nature of AGM revision (which was originally tailored for revision of only purely ontic beliefs, and can be applied to higher-order beliefs only if given a “backwards-looking” interpretation) and the fact that, semantically speaking, any Ramsey conditional must be a modal operator (more precisely, a dynamic-epistemic one). Thus, a belief about a Ramsey conditional is in fact a higher-order belief, hence (...) the AGM revision postulates are not applicable to it, except in their “backwards-looking” interpretation. But that interpretation is consistent only with a restricted (weak) version of Ramsey’s test (in-applicable to already revised theories). The solution out of the conundrum is twofold: either accept only the weak Ramsey test; or replace the AGM revision operator ∗ by a truly “dynamic” revision operator ⊗, which will not satisfy the AGM axioms, but will do something better: it will “keep up with reality”, correctly describing revision with higher-order beliefs. (shrink)

The study of a pragmatic dimension of semiotics appears only late in the history of this discipline. “Pragmatics” seems the last one called into the dispute of signs. The following study focusses on semiotics and the theory of action, stressing the distinction between “pragmatism” and “practical” matters within this philosophical discipline. The theory of “speech acts” is investigated and related to the new perspectives opened in the semiotics in order to highlight furtheravenues for research.

Can we still talk today about a therapeutically dimension of philosophy? To what extent does Heidegger's philosophy exhibit such a dimension? And how can we reconcile this aspect of Heidegger's thought with his political involvement in 1933? These are some of the questions starting from which I will try to show that Heidegger's philosophical thought presupposes indeed a therapeutic that the thinker assumed even in his own life, a life that is not reducible to his 'unforgivable failure' in 1933. I (...) will begin with an account of Being and Time's existential analytic, the main thread of which is the distinction between Dasein's authenticity and inauthenticity. Next I will try to grasp some of the importance of Heidegger's investigation regarding Dasein's determination as a 'thinker and speaker of being (Sein)', that is, regarding ec-sistence. I will then try to account for the meaning of the 'question regarding technology' and implicitly Heidegger's solution regarding overcoming the condition of a 'gregarious slave of Ge-stell' through cultivation of the so-called 'poetic theology.' I will conclude by signaling some life-file elements of the 'faithless monk from the Black Forest' (as Heidegger is sometimes called), elements that signal a certain correspondence between the philosopher's life and the therapeutic aspect present implicitly in his philosophy. (shrink)