Epistemic Logic

This book concerns the foundations of epistemic modality and hyperintensionality and their applications to the philosophy of mathematics. I examine the nature of epistemic modality, when the modal operator is interpreted as concerning both apriority and conceivability, as well as states of knowledge and belief. The book demonstrates how epistemic modality and hyperintensionality relate to the computational theory of mind; metaphysical modality and hyperintensionality; the types of mathematical modality and hyperintensionality; to the epistemic status of large cardinal axioms, undecidable propositions, and abstraction principles in the philosophy of mathematics; to the modal and hyperintensional profiles of the logic of rational intuition; and to the types of intention, when the latter is interpreted as a hyperintensional mental state. Chapter 2 argues for a novel type of expressivism based on the duality between the categories of coalgebras and algebras, and argues that the duality permits of the reconciliation between modal and hyperintensional cognitivism and modal and hyperintensional expressivism. I also develop a novel, topic-sensitive truthmaker semantics for dynamic epistemic logic, and develop a novel, dynamic two-dimensional semantics grounded in two-dimensional hyperintensional Turing machines. Chapter 3 provides an abstraction principle for epistemic (hyper-)intensions. Chapter 4 advances a topic-sensitive two-dimensional truthmaker semantics, and provides three novel interpretations of the framework along with the epistemic and metasemantic. Chapter 5 applies the fixed points of the modal μ-calculus in order to account for the iteration of epistemic states in a single agent, by contrast to availing of modal axiom 4 (i.e. the KK principle). The fixed point operators in the modal μ-calculus are rendered hyperintensional, which yields the first hyperintensional construal of the modal μ-calculus in the literature and the first application of the calculus to the iteration of epistemic states in a single agent instead of the common knowledge of a group of agents. Chapter 6 advances a solution to the Julius Caesar problem based on Fine's `criterial' identity conditions which incorporate conditions on essentiality and grounding. Chapter 7 provides a ground-theoretic regimentation of the proposals in the metaphysics of consciousness and examines its bearing on the two-dimensional conceivability argument against physicalism. The topic-sensitive epistemic two-dimensional truthmaker semantics developed in chapters 2 and 4 is availed of in order for epistemic states to be a guide to metaphysical states in the hyperintensional setting.

Chapters 8-12 provide cases demonstrating how the two-dimensional hyperintensions of hyperintensional, i.e. topic-sensitive epistemic two-dimensional truthmaker, semantics, solve the access problem in the epistemology of mathematics. Chapter 8 examines the interaction between my hyperintensional semantics and the axioms of epistemic set theory, large cardinal axioms, the Epistemic Church-Turing Thesis, the modal axioms governing the modal profile of Ω-logic, Orey sentences such as the Generalized Continuum Hypothesis, and absolute decidability. These results yield inter alia the first hyperintensional Epistemic Church-Turing Thesis and hyperintensional epistemic set theories in the literature. Chapter 9 examines the modal and hyperintensional commitments of abstractionism, in particular necessitism, and epistemic hyperintensionality, epistemic utility theory, and the epistemology of abstraction. I countenance a hyperintensional semantics for novel epistemic abstractionist modalities. I suggest, too, that higher observational type theory can be applied to first-order abstraction principles in order to make first-order abstraction principles recursively enumerable, i.e. Turing machine computable, and that the truth of the first-order abstraction principle for two-dimensional  hyperintensions is grounded in its being possibly recursively enumerable and the machine being physically implementable. Chapter 10 examines the philosophical significance of hyperintensional Ω-logic in set theory and discusses the hyperintensionality of metamathematics. Chapter 11 provides a modal logic for rational intuition and provides a hyperintensional semantics. Chapter 12 avails of modal coalgebras to interpret the defining properties of indefinite extensibility, and avails of hyperintensional epistemic two-dimensional semantics in order to account for the interaction between interpretational and objective modalities and the truthmakers thereof. This yields the first hyperintensional category theory in the literature. I invent a new mathematical trick in which first-order structures are treated as categories, and Vopenka's principle can be satisfied because of the elementary embeddings between the categories and generate Vopenka cardinals in the category of Set in category theory. Chapter 13 examines modal responses to the alethic paradoxes. Chapter 14 examines, finally, the modal and hyperintensional semantics for the different types of intention and the relation of the latter to evidential decision theory.

We draw parallels between several closely related logics that combinein different proportions -elements of game theory, computation tree logics, and epistemic logics to reason about agents and their abilities. These are: the coalition game logics CL and ECL introduced by Pauly in 2000, the alternating-time temporal logic ATL developed by Alur, Henzinger and Kupferman between 1997 and 2002, and the alternating-time temporal epistemic logic ATEL by . In particular, we establish some subsumption and equivalence results for their semantics, as well as interpretation of the alternating-time temporal epistemic logic into ATL.

For over half a century, throughout attempts to unify the standard model with general relativity, scientists have confronted the "problem of inconsistent models," which occurs when scientific models, regarded as perspectives on physical systems, make contradictory claims about things in the world. Perspectival realists have proposed to solve to this problem by showing that while scientific models are inherently perspectival, they can make true claims about one reality, relative to the perspectives they offer. Critics of this position have pointed out that this would leave us with no way to discern between benign inconsistencies between models and genuine contradictions that demand resolution; these critics, however, have also failed to find a way to do this. This paper offers a criterion for making this distinction, by way of a formal analysis of perspective and its role in scientific models and theories, without sacrificing the key insights provided by perspectival realism.

Presentamos una lógica epistémica bimodal trivaluada que tiene como objetivo, formalizar la interacción entre ciertas creencias que conducen a conocimiento. Mientras que el ejemplo presentado muestra este resultado con el simple juego de sudoku, nuestra intención es extraer lecciones para situaciones epistémicas más amplias donde aparecen revisión de creencias y agentes cognitivos imperfectos. Nuestro intento debe ser entendido como una instancia de epistemología formal, cuyo objetivo es arrojar luz sobre los problemas epistemológicos tradicionales por medio de herramientas formales.

This is my completed PhD-thesis I never had chance to defend. It studies the famous problem in epistemic logic (logical omniscience) and proposes a method to solve it using some elements of the intuitionistic logic. It is written in Ukrainian but contains an English short summary.

This article argues that, propaedeutic to the construction of an Objectivist aesthetics, scholars must refute the irrational/immoral philosophical premises that have been destroying the philosophy of art. Due to the troubling combination of its contemporaneity, extremism, and considerable influence, poststructuralism, which, since the 1960s, has served as the default philosophical foundation for philosophers of art, is the target of this article.

Preference is a basic notion in human behaviour, underlying such varied phenomena as individual rationality in the philosophy of action and game theory, obligations in deontic logic (we should aim for the best of all possible worlds), or collective decisions in social choice theory. Also, in a more abstract sense, preference orderings are used in conditional logic or non-monotonic reasoning as a way of arranging worlds into more or less plausible ones. The field of preference logic (cf. Hansson ) studies formal systems that can express and analyze notions of preference between various sorts of entities: worlds, actions, or propositions. The art is of course to design a language that combines perspicuity and low complexity with reasonable expressive power. In this paper, we take a particularly simple approach. As preferences are binary relations between worlds, they naturally support standard unary modalities. In particular, our key modality ♦ϕ will just say that is ϕ true in some world which is at least as good as the current one. Of course, this notion can also be indexed to separate agents. The essence of this language is already in [4], but our semantics is more general, and so are our applications and later language extensions. Our modal language can express a variety of preference notions between propositions. Moreover, as already suggested in [9], it can "deconstruct" standard conditionals, providing an embedding of conditional logic into more standard modal logics. Next, we take the language to the analysis of games, where some sort of preference logic is evidently needed ([23] has a binary modal analysis different from ours). We show how a qualitative unary preference modality suffices for defining Nash Equilibrium in strategic games, and also the Backward Induction solution for finite extensive games. Finally, from a technical perspective, our treatment adds a new twist. Each application considered in this paper suggests the need for some additional access to worlds before the preference modality can unfold its true power. For this purpose, we use various extras from the modern literature: the global modality, further hybrid logic operators, action modalities from propositional dynamic logic, and modalities of individual and distributed knowledge from epistemic logic. The total package is still modal, but we can now capture a large variety of new notions. Finally, our emphasis in this paper is wholly on expressive power. Axiomatic completeness results for our languages can be found in the follow-up paper [27].

Defining subalternations with the same semantic term will result in a semantic collapse of terms. If Flew's "Presumption of Atheism" is accepted, such that atheism should be thought of in the negative case, where subalternations  for both "positive atheism" and "negative atheism" are denoted by the same term of "atheism", it can then be logically demonstrated by way of a semiotic square of opposition that it will effectively result in the possibility of someone concurrently being semantically an atheist, theist and agnostic. This semantic collapse of terms lowers the axiological value of the term "atheism", and as such, is sufficient grounds to reject Flew's argument.

Alvin Plantinga, analitik felsefe düşüncesi içerisinde yetişmiş ve bu gelenek içinde teistik din felsefesinin oluşumuna katkıda bulunmuş bir filozoftur. Ayrıca teizmin savunusu için yaptığı çalışmalarla, çeşitli üniversitelerden aldığı onur ödülleri ve 2017 yılında kazandığı Templeton Prize ödülüyle, haklı bir üne kavuşmuş bir şahsiyettir.  Bu çalışmayı yapmamızdaki en önemli amaç, Plantinga’nın dini epistemoloji üzerine yaptığı çalışmaları analiz edip bu düşüncelerinin ardalanına dair bir tespitte bulunmaktır. Bu çalışmada yararlandığımız öncelikli kaynaklar, Plantinga’nın Nicholas Wolterstorff ile birlikte kaleme aldığı “Faith and Rationality” adlı eser ile birlikte son dönem epistemik fikirlerinin çerçevesini belirleyen üç ciltlik “Warrant and Proper Function”, “Warrant: The Current Debate”, “Warranted: Christian Belief”  isimli eserler olmuştur. Plantinga’nın ilk dönem epistemoloji çalışmalarının gayesini bir tür olumsuzlama diyebileceğimiz klasik temelciliğin ve evidentializmin eleştirisi oluştururken, ikinci döneminde bu eleştirilerden yola çıkarak Tanrı inancının haklı bir temelde ve güvenceye sahip olduğunu gösterme amacına yönelmiştir. Plantinga’nın teolojik fikirlerini oluşturan Kalvinci ekol, onun dini epistemolojisinin de özünü oluşturmaktadır. Plantinga’nın dini epistemolojisini iki boyutlu olarak değerlendirdiğimizde, içe dönük olarak Hristiyan inancıyla ilgilense de çalışmalarının dışsal yönünü daha genel olarak teizmin Tanrı’sı ve onun rasyonelliği oluşturmaktadır.  Açıkçası Plantinga’nın epistemolojik külliyatı bir tür kavram zenginliğini de beraberinde getirmektedir. Çalışmamız içerisinde ele aldığımız kadarıyla uygun işlevsellik, tasarım planı, güvence (warrant) gibi kavramlar onun Tanrı inancının epistemik mahiyetini ortaya koymak için ne derece kararlı olduğunu göstermektedir.  Netice itibariyle Tanrı inancının ve onun bilgisinin rasyonel olabileceğini ifade eden Plantinga, her ne kadar Hristiyan inancının belli bir koluna mensup olsa da diğer mezhepleri dışlamaz. Ayrıca Plantinga, birçok çalışmasında belirttiği üzere projesinin Yahudilik, İslam gibi diğer teistik dinlere yönelik olduğunu da belirtmektedir.

"Pluralistic ignorance" is a phenomenon mainly studied in social psychology. Viewed as an epistemic phenomenon, one way to define it is as a situation where "no one believes, but everyone believes that everyone else believes". In this paper various versions of pluralistic ignorance are formalized using epistemic/doxastic logic (based on plausibility models). The motive is twofold. Firstly, the formalizations are used to show that the various versions of pluralistic ignorance are all consistent, thus there is nothing in the phenomenon that necessarily goes against logic. Secondly, pluralistic ignorance, is on many occasions, assumed to be fragile. In this paper, however, it is shown that pluralistic ignorance need not be fragile to announcements of the agents' beliefs. Hence, to dissolve pluralistic ignorance in general, something more than announcements of the subjective views of the agents is needed. Finally, suggestions to further research are outlined.

Sin dagli inizi della riflessione filosofica, di particolare interesse è stato il comprendere il modo attraverso il quale viene argomentata una tesi che si vuol sostenere. Generalmente, gli argomenti sono descritti come il prodotto dell’argomentazione: ciò significa che, quando si vuol asserire una determinata tesi, occorre fornire delle ragioni a sostegno della tesi asserita. Alla luce di ciò un argomento è articolato in premesse dell’argomento, le quali forniscono il sostegno alla conclusione dell’argomento, che è la tesi asserita.
Ciò che interessa alla logica è la relazione che intercorre tra premesse e conclusione dell’argomento. Sulla base di tale relazione è opportuno distinguere due tipi di argomenti diversi: da un lato si hanno gli argomenti deduttivi, dall’altro gli argomenti induttivi. Gli argomenti deduttivi sono caratterizzati dal fatto che tra premesse e conclusione dell’argomento vige una relazione necessaria: ciò significa che, se l’argomento è valido e le premesse sono vere, la conclusione non può che essere vera, ossia la verità della conclusione è implicata dalla verità delle premesse. Invece, in un argomento induttivo non vige questa relazione necessaria tra premesse e conclusione: le premesse possono fornire un sostegno solamente parziale alla conclusione. Infatti, alcuni logici del Novecento hanno parlato di implicazione logica parziale.
Il presente lavoro si pone l’obiettivo di comprendere il funzionamento di un argomento induttivo, cercando di interpretare la relazione tra premesse e conclusione di esso, ricorrendo alla nozione di probabilità. In secondo luogo si analizza l’approccio logicista a tale nozione, il quale si è sviluppato a partire dal XX secolo.
Nel primo capitolo si ripercorre lo sviluppo storico-filosofico del problema dell’induzione. Già nell’Organon aristotelico si ritrova la prima distinzione tra deduzione e induzione; tuttavia, nel corso della filosofia antica e medievale è evidente una connotazione negativa di questa tipologia di ragionamento. Sarà Bacone, nel XVII secolo, a impegnarsi in una riabilitazione del ragionamento induttivo, in special modo nell’indagine scientifica. Secondo Bacone, l’induzione consiste nella conferma di un’ipotesi basandosi sui dati derivanti dall’osservazione empirica e dal loro seguente confronto.
Nel XVIII secolo, Hume si impegnò nella trattazione specifica dell’induzione, cercando di formulare, in maniera maggiormente chiara, il problema: non a caso egli parla esplicitamente di “problema dell’induzione”. Nel Trattato sulla Natura Umana, Hume sottolinea che negli argomenti in cui le premesse sono basate su dati empirici, ossia su dati osservabili, non vi può essere un nesso necessario che unisce le premesse alla conclusione; ciò accade perché egli non condivide il principio dell’uniformità della natura: questo significa che gli eventi futuri non necessariamente si ripresentano come nel passato.
In un tipico argomento deduttivo, la relazione logica che intercorre tra premesse e conclusione è quello dell’implicazione logica. Invece, in un argomento induttivo, la relazione tra premesse e conclusione può essere chiamata implicazione logica parziale. Una delle strade intraprese al fine di chiarire tale relazione logica consiste nell’applicazione della nozione di probabilità.
Gli albori della riflessione intorno alla probabilità possono essere rintracciati nel corso del XVII secolo, grazie anche ai contributi dati in ambito matematico; importante è il contribuito dato da Leibniz. Inoltre occorre sottolineare che la riflessione circa la nozione di probabilità nasce con il proposito di risolvere questioni afferenti al gioco d’azzardo. Leibniz, ad esempio, narrava che il Cavalier De Mére, offrì occasioni di studio sfidando, su questioni di probabilità, i principali studiosi del tempo. Importanti spunti sul tema sono stati offerti da Christian Huygens, Jacob Bernoulli, Blaise Pascal, Laplace e altri.
Nel secondo capitolo dell’elaborato si affronta specificatamente l’approccio logicista alla nozione di probabilità, il quale prende avvio specificatamente negli anni venti del Novecento, grazie alle riflessioni di J. M. Keynes e, in particolare, L. Wittgenstein.
Keynes, in A Treatise on Probability, delinea un sistema logico-formale in cui la probabilità interviene quale nesso logico tra le proposizioni di un’inferenza induttiva. Dato l’insieme h delle premesse e la conclusione x, è possibile formulare un argomento x/h; se questo è un argomento induttivo, è possibile inferire x da h con un certo grado di credenza razionale p: p si identifica con la probabilità di x dato h (p=x/h).
Importante è la distinzione keynesiana tra probabilità e peso di un argomento. La probabilità è legata alla valutazione del rapporto che intercorre tra le premesse e la conclusione di un argomento induttivo; invece, il peso dell’argomento è una nozione che esprime un giudizio oggettivo e complessivo sull’argomento. Keynes formalizza il peso dell’argomento nel rapporto tra la conoscenza rilevante e la somma della conoscenza rilevante e dell’ignoranza rilevante [V(x/h)=K/(K+I)]. Come ricordato, il principale contributo allo sviluppo dell’approccio logicista alla probabilità è stato dato da L. Wittgenstein. Nello scritto viene delineata la teoria raffigurativa del linguaggio sviluppata da Wittgenstein nel Tractatus logico- philosophicus: vengono altresì spiegate, in linea generale, le principali nozioni presenti nell’opera al fine di introdurre la proposizione 5.15 del Tractatus in cui Wittgenstein propone la sua posizione circa la probabilità. Egli definisce la probabilità di una proposizione h, data un’altra proposizione e, in termini di fondamenti di verità. Pertanto, la probabilità che e dà ad h è eguale al rapporto tra il numero dei fondamenti di verità comuni a e e ad h, e il numero dei fondamenti di verità di e.
Il pensiero di Wittgenstein influenza particolarmente le riflessioni dei pensatori che partecipano al cosiddetto Wiener Kreis. Particolarmente importante fu l’influsso di Wittgenstein sulla filosofia di Friedrich Waismann. Egli, per definire la probabilità, ricorre alla nozione, già presente nel Tractatus, di raggio d’azione (spielraum), asserendo che la probabilità di un ipotesi h, data l’evidenza e, è uguale al rapporto tra la congiunzione dei raggi d’azione dell’ipotesi h e dell’evidenza e, e il raggio d’azione dell’evidenza e.
Il terzo capitolo del presente lavoro è interamente dedicato alla filosofia di Rudolf Carnap. Nella prima parte del capitolo si cerca di evidenziare i punti salienti del pensiero di Carnap, citando le sue principali opere: tra queste vi sono Der Logische Aufbau der Welt, Logische Syntax der Sprache, Testability and Meaning, Introduction to Semantics e Meaning and Necessity.
Nella seconda parte del capitolo ci si sofferma sull’interpretazione carnapiana della nozione di probabilità e sul problema dell’induzione in Carnap. Egli associa la probabilità alla nozione di grado di conferma e, quindi, parla della probabilità condizionale di h data e come del grado di conferma dell’ipotesi h, data l’evidenza osservativa e. Sviluppando e precisando le idee di Wittgenstein e Waismann nel quadro teorico della sua semantica dei mondi possibili, Carnap definisce la probabilità di h data e, ossia il grado di conferma che e conferisce ad h, come il rapporto tra l’intersezione insiemistica degli ambiti di h e di e, e l’ambito di e.

We need to understand the impossible. Francesco Berto and Mark Jago start by considering what the concepts of meaning, information, knowledge, belief, fiction, conditionality, and counterfactual supposition have in common. They are all concepts which divide the world up more finely than logic does. Logically equivalent sentences may carry different meanings and information and may differ in how they're believed. Fictions can be inconsistent yet meaningful. We can suppose impossible things without collapsing into total incoherence. Yet for the leading philosophical theories of meaning, these phenomena are an unfathomable mystery. To understand these concepts, we need a metaphysical, logical, and conceptual grasp of situations that could not possibly exist: Impossible Worlds. This book discusses the metaphysics of impossible worlds and applies the concept to a range of central topics and open issues in logic, semantics, and philosophy. It considers problems in the logic of knowledge, the meaning of alternative logics, models of imagination and mental simulation, the theory of information, truth in fiction, the meaning of conditional statements, and reasoning about the impossible. In all these cases, impossible worlds have an essential role to play.

Cette thèse est le résultat d'une longue et tumultueuse réflexion, conduite pendant plus de cinq années au sein des Archives Poincaré. Je ne peux que remercier vivement tous ceux qui, durant cette période, ont su m'entourer de leur bienveillance, me stimuler par leurs remarques, me renforcer par leurs compétences. Igor, Amirouche, Philippe, Manu, Pidou, Scott, Prosper, Eric … à tous, ma partie reconnaissante.

Simandan D (2005) "Pragmatic Scepticism and the Possibilities of Knowledge" Timisoara, Editura Universitatii de Vest/West University Press, 256 pp.

This book distiled my own way of understanding the relation between epistemology, ontology, and politics, and the best name I found for labelling that way is pragmatic scepticism. Throughout the book, I stay away from the temptation to give a dictionary-like definition of this philosophy. I do not even like to think of it as a philosophy. Instead, I see pragmatic scepticism as a way of being and as a way of relating. A way of being human, i.e. enmeshed in language and limited by our senses; and a way of relating, i.e. crafted by the happy and sad encounters with theories, things, and lifeís happenings. The book is structured in three parts, which together give a sense of the potentials of pragmatic scepticism: as a way of thinking about the world, as a way of approaching theoretical dilemmas, as a way of mapping one's inner contradictions. The first part of the book introduces pragmatic scepticism in relation to the general questions underwriting the philosophy of knowledge and the study of science. The second part is more specific in that it deploys the pragmatic sceptical attitude to the central metatheoretical questions of the discipline of geography. The last part of the book groups under the heading "philosophies of struggle" two more applied essays on the political economy and the political epistemology of conflicts over knowledge in the globalised landscape of higher education in general and geography in particular.

This article is focused on answering the question to what extent one can be a sceptic. Sextus Empiricus’s Outlines of Scepticism serves as a guide. In section 1, it is investigated whether three logical laws have a certain foundation or are subject to doubt. In section 2, Sextus’s way to deal with these laws is examined; the question arises how dogmatic his approach is. After that, a possible ‘reply’ by Sextus to the criticism receives attention. Section 3 is concentrated on a possible alternative to Sextus’s approach. Besides logical laws, some important methods are concerned.

Current epistemic logic models are mostly limited to either binary or prob-abilistic interpretation of knowledge. We present a logic which allows for degrees/strength of knowledge/knowing independent of probabilities. Namely, we assign fuzzy values to both the atomic propositions and accessibility relationships. We first discuss why a fuzzy approach is necessary in some scenarios. Then we present the static and dynamic version of the logic. Lastly we use it to model a logically non-omniscient agent's knowledge over a decidable theory to illustrate the usefulness and some philosophical issue of the logic.

In this paper I look at Fred Dretske’s account of information and knowledge as developed in Knowledge and The Flow of Information. In particular, I translate Dretske’s probabilistic definition of information to a modal logical framework and subsequently use this to explicate the conception of information and its flow which is central to his account, including the notions of channel conditions and relevant alternatives. Some key products of this task are an analysis of the issue of information closure and an investigation into some of the logical properties of Dretske’s account of information flow.

In this paper, I present a way to model systems of mystical reasoning using category theory. I propose that we take mystical reasoning to be mundane reasoning, lifted into a mystical context, where a mystical context is any reasoning context where God or the divinity is directly present. Mystical contexts can be modeled as monads over categories of mundane reasoning, which yield Kleisli categories that represent lifted (mystical) systems of reasoning, each equipped with its own logic.

"It is a venerable slogan due to David Hume, and inherited by the empiricist tradition, that the impossible cannot be believed, or even conceived. In Positivismus und Realismus, Moritz Schlick claimed that, while the merely practically impossible is still conceivable, the logically impossible, such as an explicit inconsistency, is simply unthinkable.

An opposite philosophical tradition, however, maintains that inconsistencies and logical impossibilities are thinkable, and sometimes believable, too. In the Science of Logic, Hegel already complained against “one of the fundamental prejudices of logic as hitherto understood”, namely that “the contradictory cannot be imagined or thought” (Hegel 1931: 430). Our representational capabilities are not limited to the possible, for we appear to be able to imagine and describe also impossibilities — perhaps without being aware that they are impossible.

Such impossibilities and inconsistencies are what this entry is about..."

One sense of 'imagination' that matters in epistemology has the word mean 'reality-oriented mental simulation' (ROMS): we suppose that something is the case; develop the supposition by importing background knowledge and beliefs; and check what is true in the imagined scenario.
What is the logic of ROMS? Imagination has a reputation for being logically anarchic. In particular, it's hyperintensional: we can imagine A without imagining a necessarily equivalent B. This work considers a Principle of Equivalence in Imagination which, if accepted, will limit the anarchy: when A and B are equivalent in imagination, one will imagine the same things after supposing either in ROMS.
What is equivalence in imagination? It is suggested that it's cognitive equivalence. A and B are cognitively equivalent for one when they play the same role in one's cognitive life: whatever one understands, concludes, etc., given either, one does, given the other. ROMS is logically modelled via variably strict modals. Two formal semantics are proposed for them: one uses possible worlds plus an algebra of topics; the other resorts to impossible worlds. The two deal with equivalence in imagination in subtly different ways.

I want to model a finite, fallible cognitive agent who imagines that p in the sense of mentally representing a scenario – a configuration of objects and properties – correctly described by p. I propose to capture imagination, so understood, via variably strict world quantifiers, in a modal framework including both possible and so-called impossible worlds. The latter secure lack of classical logical closure for the relevant mental states, while the variability of strictness captures how the agent imports information from actuality in the imagined non-actual scenarios. Imagination turns out to be highly hyperintensional, but not logically anarchic.
§1 sets the stage and impossible worlds are quickly introduced in §2. §3 proposes to model imagination via variably strict world quantifiers. §4 introduces the formal semantics. §5 argues that imagination has a minimal mereological structure validating some logical inferences. §6 deals with how imagination under-determines the represented contents. §7 proposes additional constraints on the semantics, validating further inferences. §8 describes some welcome invalidities. §9 examines the effects of importing false beliefs into the imag- ined scenarios. Finally, §10 hints at possible developments of the theory in the direction of two-dimensional semantics.

A Topic-Sensitive Intentional Modal (TSIM) is a two-place, variably strict modal with an aboutness or topicality constraint, of the form ‘X^φψ’ (read: ‘Given φ, the agent X’s that ψ’, X being some mental state or act). TSIMs do nice things for mainstream and formal epistemology, belief revision theory, and mental simulation theory. I present a basic formal semantics for TSIMs and explore three readings of ‘X^φψ’ one gets by imposing different constraints on their truth conditions: (1) as expressing knowability relative to information (‘Given total information φ, one is in the position to know that ψ’), inspired by Dretske’s view that what one can know depends on the available (empirical) information; (2) as a mental simulation operator (‘In mental simulation starting with input φ, one imagines that ψ’) capturing features of mainstream mental simulation theories, like that of Nichols and Stich; (3) as a hyperintensional belief revision operator (‘After (statically) revising by φ, one believes that ψ’), reducing the idealization of cognitive agents one finds in standard doxastic logics and AGM. I close by mentioning developments of TSIM theory currently in progress.

The work of Luciano Floridi lies at the interface of philosophy, information science and technology, and ethics, an intersection whose existence and significance he was one of the first to establish. His closely related concepts of a philosophy of information (PI), informational structural realism, information logic (IL), and information ethics (IE) provide a new ontological perspective from which moral concerns

Current dynamic epistemic logics for analyzing effects of informational events often become cumbersome and opaque when common knowledge is added for groups of agents. Still, postconditions involving common knowledge are essential to successful multi-agent communication. We propose new systems that extend the epistemic base language with a new notion of 'relativized common knowledge', in such a way that the resulting full dynamic logic of information flow allows for a compositional analysis of all epistemic postconditions via perspicuous 'reduction axioms'. We also show how such systems can deal with factual alteration, rather than just information change, making them cover a much wider range of realistic events. After a warm-up stage of analyzing logics for public announcements, our main technical results are expressivity and completeness theorems for a much richer logic that we call LCC. This is a dynamic epistemic logic whose static base is propositional dynamic logic (PDL), interpreted epistemically. This system is capable of expressing all modelshifting operations with finite action models, while providing a compositional analysis for a wide range of informational events. This makes LCC a serious candidate for a standard in dynamic epistemic logic, as we illustrate by analyzing some complex communication scenarios, including sending successive emails with both 'cc' and 'bcc' lines, and other private announcements to subgroups. Our proofs involve standard modal techniques, combined with a new application of Kleene's Theorem on finite automata, as well as new Ehrenfeucht games of model comparison.

Three classic distinctions specify that truths can be necessary versus contingent, analytic versus synthetic, and a priori versus a posteriori. The philosopher reading this article knows very well both how useful and ordinary such distinctions are in our conceptual work and that they have been subject to many and detailed debates, especially the last two. In the following pages, I do not wish to discuss how far they may be tenable. I shall assume that, if they are reasonable and non problematic in some ordinary cases, then they can be used in order to understand what kind of knowledge the maker's knowledge is. By this I mean the sort of knowledge that Alice enjoys when she holds the information (true content) that Bob's coffee is sweetened because she just put two spoons of sugar in it herself. The maker's knowledge tradition is quite important but it is not mainstream in modern and analytic epistemology and lacks grounding in terms of exactly what sort of knowledge one is talking about. My suggestion is that this grounding can be provided by a minimalist approach, based on an information-theoretical analysis. In the article, I argue that (a) we need to decouple a fourth distinction, namely informative versus uninformative, from the previous three and, in particular, from its implicit association with analytic versus synthetic and a priori versus a posteriori; (b) such a decoupling facilitates, and is facilitated by, moving from a monoagent to a multiagent approach: the distinctions qualify a proposition, a message, or some information not just in themselves but relationally, with respect to an informational agent; (c) the decoupling and the multiagent approach enable a re-mapping of currently available positions in epistemology (Classic, Innatist, Kant's and Kripke's) on these four dichotomies; (d) within such a re-mapping, two positions, capturing the nature of a witness' knowledge and of a maker's knowledge, can best be described as contingent, synthetic, a posteriori, and uninformative and as
contingent, synthetic, weakly a priori (ab anteriori), and uninformative respectively. In the conclusion, I indicate why the analysis of the maker’s knowledge has important consequences in all those cases in which the poietic (constructive) intervention on a system determines the truth of the model of that system.

This paper develops the model theory of normal modal logics based on partial “possibilities” instead of total “worlds,” following Humberstone [1981] instead of Kripke [1963]. Possibility semantics can be seen as extending to modal logic the semantics for classical logic used in weak forcing in set theory, or as semanticizing a negative translation of classical modal logic into intuitionistic modal logic. Thus, possibility frames are based on posets with accessibility relations, like intuitionistic modal frames, but with the constraint that the interpretation of every formula is a regular open set in the Alexandrov topology on the poset. The standard world frames for modal logic are the special case of possibility frames wherein the poset is discrete. The analogues of classical Kripke frames, i.e., full world frames, are full possibility frames, in which propositional variables may be interpreted as any regular open sets.

We develop the beginnings of duality theory, definability/correspondence theory, and completeness theory for possibility frames. The duality theory, relating possibility frames to Boolean algebras with operators (BAOs), shows the way in which full possibility frames are a generalization of Kripke frames. Whereas Thomason [1975a] established a duality between the category of Kripke frames with p-morphisms and the category of complete (C), atomic (A), and completely additive (V) BAOs with complete BAO-homomorphisms (these categories being dually equivalent), we establish a duality between the category of full possibility frames with possibility morphisms and the category of CV-BAOs, i.e., allowing non-atomic BAOs, with complete BAO-homomorphisms (the latter category being dually equivalent to a reflective subcategory of the former). This parallels the connection between forcing posets and Boolean-valued models in set theory, but now with accessibility relations and modal operators involved. Generalizing further, we introduce a class of principal possibility frames that capture the generality of V-BAOs. If we do not require a full or principal frame, then every BAO has an equivalent possibility frame, whose possibilities are proper filters in the BAO. With this filter representation, which does not require the ultrafilter axiom, we are lead to a notion of filter-descriptive possibility frames. Whereas Goldblatt [1974] showed that the category of BAOs with BAO-homomorphisms is dually equivalent to the category of descriptive world frames with p-morphisms, we show that the category of BAOs with BAO-homomorphisms is dually equivalent to the category of filter-descriptive possibility frames with p-morphisms. Applying our duality theory to definability theory, we prove analogues for possibility semantics of theorems of Goldblatt [1974] and Goldblatt and Thomason [1975] characterizing modally definable classes of frames. In addition, we discuss analogues for possibility semantics of first-order correspondence results in the style of Lemmon and Scott [1977], Sahlqvist [1975], and van Benthem [1976a]. Finally, applying our duality theory to completeness theory, we show that there are continuum many normal modal logics that can be characterized by full possibility frames but not by Kripke frames, that all Sahlqvist logics can be characterized by full possibility frames that contain no worlds, and that all normal modal logics can be characterized by filter-descriptive possibility frames.

The single most important statement that can be made with regard to the logical status of human and physical geographical reasoning is that it belongs to the class of non-monotonic reasoning. In other words,  geographical reasoning is defeasible (i.e. earlier drawn conclusions can be defeated by the addition of new facts, some of which are generated by the very application of our ideas outside academe) and non-demonstrative (i.e. our beliefs about reality cannot be demonstrated once and for ever; we must do with building provisional arguments based on the current weight of the evidence, which itself changes with the times). Indeed, unlike mathematics, which is a closed world of formalisms that relies heavily on deduction, demonstration, and proof, geography studies and attempts to improve the real, messy world out there. Because that wild, unruly world is always in a process of becoming, the conclusions drawn yesterday may have to be abandoned today, and so on, without end in sight. The core virtue of geographical reasoning is not certainty, but adaptability. As the world changes, so do geography’s entertained beliefs about how to improve it. The point we are trying to make is that an alternative window into the nature of geographical reasoning, besides the one provided by the discipline’s key concepts, offers an opening toward the more subtle problematic of the mechanisms by which the updating of geographical beliefs operate.

Agradeço, primeiramente, a Deus, sem o qual não haveria o que pudesse ser estudado ou conhecido ou mesmo quem pudesse dar-se ao trabalho de fazê-lo. Sou grato a Jesus Cristo por ter se sacrificado em meu lugar para que meus pecados pudessem ser expiados e para que eu pudesse ser justificado a fim de ganhar a vida eterna;

La paradoja de la cognoscibilidad, o paradoja de Fitch, es un argumento que prueba, en caso de que se lo acepte como correcto, que si todas las verdades son cognoscibles, entonces todas las verdades son de hecho conocidas. Dicho de otro modo, la cognoscibilidad colapsa con la omnisciencia:

Doxastic voluntarism maintains that we have voluntary control over our beliefs. It is generally denied by contemporary philosophers. I argue that doxastic voluntarism is true: normally, and insofar as we are rational, we are able to suspend belief and, provided we have a natural inclination to believe, we are able to rescind that suspension, and thus to choose to believe. I show that the arguments that have been offered against doxastic voluntarism fail; and that, if the denial of doxastic voluntarism is part of a strategy to defeat scepticism, it is inept, because knowledge presupposes doubt.

Backward and forward induction can be viewed as two styles of reasoning in dynamic games. Since each prescribes taking a different attitude towards the past moves of the other player(s), the strategies  they identify as rational are sometimes  incompatible. Our goal is to study players who are able to deliberate between backward and forward induction, as well as conditions under which one is superior to the other. This extended abstract is our first step towards this goal. We present an extension of Stalnaker's game models, in which the players can make ``trembling hand'' mistakes. This means that when a player observes an unexpected move, she has to figure out whether it is a result of a deliberate choice or a mistake, thereby committing herself to one of the two styles of reasoning.

O presente artigo visa estabelecer uma ponte entre a dimensão semântica dos preceitos da lei natural e a matriz lógica e semiótica de suas proposições normativas. Partimos do suposto de que há uma trajetória lógica entre a norma e seu campo designativo, a partir da qual a proposição normativa é forjada e constitui-se como veículo de inteligibilidade do âmbito referencial dos primeiros princípios da razão prática.

This article provides a theoretical and philosophical analysis of the account of rational expectations in games recently developed by Aumann and Dreze (Aumann and Dreze 2008) on the basis of the correlated equilibrium solution concept. Aumann and Dreze identify a player's rational expectation with his conditional payoff to a correlated equilibrium in a given " game situation ". This definition depends on the satisfaction of several assumptions in an epistemic game-theoretic framework: the Information Partition Assumption, the Common Prior Assumption and the Common Knowledge of Bayesian Rationality Assumption. I evaluate these three assumptions on the basis of a particular view about intentionality, Daniel Dennett's intentional stance functionalism. Once rational expectations are interpreted along this Dennettian view, one is no longer committed with endowing the players with implausible cognitive abilities. They rather reflect and explain real patterns at the behavioral level. I argue that as an instantiation of externalism in the philosophy of mind, the Dennettian view provides a plausible defense of the Information Partition Assumption and also offers a new – though not entirely convincing – interpretation of the Common Prior Assumption. However, it fails to provide a satisfactory rationale for the Common Knowledge of Bayesian Rationality Assumption.