Closed timelike curves (CTCs) appear in many solutions of the Einstein equation, even with reasonable matter sources. These solutions appear to violate causality and so are considered problematic. Since CTCs reflect the global properties of a spacetime, one can attempt to extend a local CTC-free patch of such a spacetime in a way that does not give rise to CTCs. One such procedure is informally known as unwrapping. However, changes in global identifications tend to lead to local effects, and unwrapping (...) is no exception, as it introduces a special kind of singularity, called quasi-regular. This “unwrapping” singularity is similar to the string singularities. We define an unwrapping of a (locally) axisymmetric spacetime as the universal cover of the spacetime after one or more of the local axes of symmetry is removed. We give two examples of unwrapping of essentially 2+1 dimensional spacetimes with CTCs, the Gott spacetime and the Gödel spacetime. We show that the unwrapped Gott spacetime, while singular, is at least devoid of CTCs. In contrast, the unwrapped Gödel spacetime still contains CTCs through every point. A “multiple unwrapping” procedure is devised to remove the remaining circular CTCs. We conclude that, based on the given examples, CTCs appearing in the solutions of the Einstein equation are not simply a mathematical artifact of coordinate identifications. Alternative extensions of spacetimes with CTCs tend to lead to other pathologies, such as naked quasi-regular singularities. (shrink)

In 1933 Godel introduced a calculus of provability (also known as modal logic S4) and left open the question of its exact intended semantics. In this paper we give a solution to this problem. We find the logic LP of propositions and proofs and show that Godel's provability calculus is nothing but the forgetful projection of LP. This also achieves Godel's objective of defining intuitionistic propositional logic Int via classical proofs and provides a Brouwer-Heyting-Kolmogorov style provability semantics for Int which (...) resisted formalization since the early 1930s. LP may be regarded as a unified underlying structure for intuitionistic, modal logics, typed combinatory logic and λ-calculus. (shrink)

Inspired by Hintikka’s ideas on constructivism, we are going to ‘effectivize’ the game-theoretic semantics for independence-friendly first-order logic, but in a somewhat different way than he did in the monograph ‘The Principles of Mathematics Revisited’. First we show that Nelson’s realizability interpretation—which extends the famous Kleene’s realizability interpretation by adding ‘strong negation’—restricted to the implication-free first-order formulas can be viewed as an effective version of GTS for FOL. Then we propose a realizability interpretation for IF-FOL, inspired by the so-called ‘trump (...) semantics’ which was discovered by Hodges, and show that this trump realizability interpretation can be viewed as an effective version of GTS for IF-FOL. Finally we prove that the trump realizability interpretation for IF-FOL appropriately generalises Nelson’s restricted realizability interpretation for the implication-free first-order formulas. (shrink)

In this paper, we provide a semantic analysis of the well-known knowability paradox stemming from the Church–Fitch observation that the meaningful knowability principle /all truths are knowable/, when expressed as a bi-modal principle F --> K♢F, yields an unacceptable omniscience property /all truths are known/. We offer an alternative semantic proof of this fact independent of the Church–Fitch argument. This shows that the knowability paradox is not intrinsically related to the Church–Fitch proof, nor to the Moore sentence upon which it (...) relies, but rather to the knowability principle itself. Further, we show that, from a verifiability perspective, the knowability principle fails in the classical logic setting because it is missing the explicit incorporation of a hidden assumption of /stability/: ‘the proposition in question does not change from true to false in the process of discovery.’ Once stability is taken into account, the resulting /stable knowability principle/ and its nuanced versions more accurately represent verification-based knowability and do not yield omniscience. (shrink)

We describe a general logical framework, Justification Logic, for reasoning about epistemic justification. Justification Logic is based on classical propositional logic augmented by justification assertions t: F that read t is a justification for F. Justification Logic absorbs basic principles originating from both mainstream epistemology and the mathematical theory of proofs. It contributes to the studies of the well-known Justified True Belief vs. Knowledge problem. We state a general Correspondence Theorem showing that behind each epistemic modal logic, there is a (...) robust system of justifications. This renders a new, evidence-based foundation for epistemic logic. As a case study, we offer a resolution of the GoldmanRed Barns in Justification Logic. Furthermore, we formalize the well-known Gettier example and reveal hidden assumptions and redundancies in Gettier’s reasoning. (shrink)

This article examines a still contentious question: how conservative and liberal elements are combined in Boris N. Chicherin’s worldview and political doctrine. It considers several points of view...

Im Zentrum der Monographie von Claudia Rapp steht die Figur des christlichen Bischofs im Kontext der spätantiken Gesellschaft. Das Buch besteht aus zwei Teilen und einem Epilog. Der erste Teil (S. 1–152) erfüllt eine zweifache Aufgabe: Er bietet (1.) eine Übersicht über die relevante Forschungsliteratur und Positionierung der vorliegenden Arbeit in der Forschungslandschaft und (2.) die Präsentation des von der Verf. entworfenen Erklärungsmodells, das die gesamte Untersuchung konzeptuell bestimmt. Im zweiten Teil (S. 155–289) betrachtet die Verf. die Entwicklung der Rolle (...) des christlichen Bischofs im Kontext spätantiker Städte und Römischen Reiches vom 3. bis zum 6. Jahrhundert anhand von archäologischem, hagiographischem und juristischem Quellenmaterial. Im Epilog (S. 290–302) wird die Figur des Bischofs im Spiegel der Grabinschriften prominenter Amtsträger skizziert. Ein Quellen- und Literaturverzeichnis sowie ein Index beschließen den Band (S. 303–346). (shrink)

Uncertainty can’t be understood without taking into account both properties of the problem situation and agent’s knowledge about it. The correspondence of knowledge and situation of decision-making is crucial for understanding the onto-epistemological nature of uncertainty. At the same time, this correspondence is the key topic in virtue epistemology, especially in its ‘non-classical’, regulatory, branch, related to works of R. Roberts and W.J. Wood. In this article, genetic consultation is chosen as an example of such a problematic situation since a (...) doctor and a patient explicitly deal with the uncertainty of genetic risks. The problems of communication and joint decision-making in the context of medical-genetic consultation are comprehensively described in bioethics. At the same time, its social dimension is limited to the direct interaction of two individual agents, that allows us to use it as a model for constructing the ethics of uncertainty. In this article, four forms of uncertainty are identified: descriptive, normative and radical uncertainties, and translation uncertainty. Referring to the approaches of virtue epistemology, the author brings each of these forms into conformity with the proposed regulatory principle. The regulations assume that generating or disseminating knowledge under conditions of uncertainty require taking into account the incompleteness of the presented model of reality in its four aspects. A modelled fragment of reality could change in a predictable (descriptive uncertainty) or unexpected (radical uncertainty) way. The goals and values of a model’s user can not be hierarchically ordered, and may also change in the future (normative uncertainty). User’s interpretations of the model may be diverse, and can never be strictly defined by the intentions of the model’s author (indeterminancy of translation, or uncertainty whether success of co-reference is achieved). (shrink)

Tracing how the logic of inoperativity works in the domains of language, law, history and humanity, 'Agamben and Politics' systematically introduces the fundamental concepts of Agamben's political thought and a critically interprets his insights in the wider context of contemporary philosophy.

Here is an account of recent investigations into the two main concepts of negation developed in the constructive logic: the negation as reduction to absurdity, and the strong negation. These concepts are studied in the setting of paraconsistent logic.

In a rather general setting, we prove a number of basic theorems concerning computational complexity of derivability in adaptive logics. For that setting, the so-called standard format of adaptive logics is suitably adopted, and the corresponding completeness results are established in a very uniform way.

This paper argues that unusual coincidences, particularly those involving historical events, can be viewed as design patterns, suggesting an intelligent influence over the course of events. A compelling case examined in detail using probability theory concerns the presidencies of Abraham Lincoln (1809–1865) and John F. Kennedy (1917–1963). This and other coincidences involving historical figures disfavor the materialistic perspective and point to the presence of an intelligent agent acting on a global scale, beyond the arrow of time, influencing human lives and (...) the course of history. (shrink)

N4-lattices provide algebraic semantics for the logic N4, the paraconsistent variant of Nelson's logic with strong negation. We obtain the representation of N4-lattices showing that the structure of an arbitrary N4-lattice is completely determined by a suitable implicative lattice with distinguished filter and ideal. We introduce also special filters on N4-lattices and prove that special filters are exactly kernels of homomorphisms. Criteria of embeddability and to be a homomorphic image are obtained for N4-lattices in terms of the above mentioned representation. (...) Finally, subdirectly irreducible N4-lattices are described. (shrink)

We define a realizability interpretation of Aczel's Constructive Set Theory CZF into Explicit Mathematics. The final results are that CZF extended by Mahlo principles is realizable in corresponding extensions of T 0 , thus providing relative lower bounds for the proof-theoretic strength of the latter.

This work treats the problem of axiomatizing the truth and falsity consequence relations, ⊨ t and ⊨ f, determined via truth and falsity orderings on the trilattice SIXTEEN 3 (Shramko and Wansing, 2005). The approach is based on a representation of SIXTEEN 3 as a twist-structure over the two-element Boolean algebra.

The relationships between various modal logics based on Belnap and Dunn’s paraconsistent four-valued logic FDE are investigated. It is shown that the paraconsistent modal logic \, which lacks a primitive possibility operator \, is definitionally equivalent with the logic \, which has both \ and \ as primitive modalities. Next, a tableau calculus for the paraconsistent modal logic KN4 introduced by L. Goble is defined and used to show that KN4 is definitionally equivalent with \ without the absurdity constant. Moreover, (...) a tableau calculus is defined for the modal bilattice logic MBL introduced and investigated by A. Jung, U. Rivieccio, and R. Jansana. MBL is a generalization of BK that in its Kripke semantics makes use of a four-valued accessibility relation. It is shown that MBL can be faithfully embedded into the bimodal logic \ over the non-modal vocabulary of MBL. On the way from \ to MBL, the Fischer Servi-style modal logic \ is defined as the set of all modal formulas valid under a modified standard translation into first-order FDE, and \ is shown to be characterized by the class of all models for \. Moreover, \ is axiomatized and this axiom system is proved to be strongly sound and complete with respect to the class of models for \. Moreover, the notion of definitional equivalence is suitably weakened, so as to show that \ and \ are weakly definitionally equivalent. (shrink)

The word “encyclopedia” comes to us from the Greek or, more precisely, is the deformed transcription, through Latin, of a erase in which we recognize a word composed of two elements, enkyklios and paideia, found in Quintilian in the ancient editions of De institutione oratoria (I, 10, 1). The expression itself, enkyklios paideia, appears only later, in the Hellenistic Age, under Roman domination, beginning with Dionysius of Halicarnassus (around the first century B.C.), but the concept goes back to the Eleatics, (...) especially to Hippias of Elis who, if we can believe the account in Plato's Dialogues, taught this total knowledge, later known with the term enkyklopaideia. (shrink)

In the following paper we relate to the terms such as ‘true’ and ‘real’ in conjecture with dual character concepts such as ‘scientist’ and ‘artist’. They are often integrated into phrases broadly viewed as persuasive definitions. We argue that persuasive definitions are usually intended to marginalize individuals, sub-groups, and even objects, within a group. They may also be employed to elevate or preserve the status of a group by disassociating it with its marginal members, their actions, and characteristics. For example, (...) ‘true’ art may be stipulatively defined as having certain features to persuade us to accept the marginalization of those objects of art that lack them, and to elevate the social status of the authors of the objects that have them. ‘No true Scotsman is cruel’ is uttered to distance the normative Scots from those who run afoul, so that they can maintain untarnished reputation and positive identity. (shrink)

We compare the logic HYPE recently suggested by H. Leitgeb as a basic propositional logic to deal with hyperintensional contexts and Heyting-Ockham logic introduced in the course of studying logical aspects of the well-founded semantics for logic programs with negation. The semantics of Heyting-Ockham logic makes use of the so-called Routley star negation. It is shown how the Routley star negation can be obtained from Dimiter Vakarelov’s theory of negation and that propositional HYPE coincides with the logic characterized by the (...) class of all involutive Routley star information frames. This result provides a much simplified semantics for HYPE and also a simplified axiomatization, which shows that HYPE is identical with the modal symmetric propositional calculus introduced by G. Moisil in 1942. Moreover, it is shown that HYPE can be faithfully embedded into a normal bi-modal logic based on classical logic. Against this background, we discuss the notion of hyperintensionality. (shrink)

ABSTRACT In 1933 Gödel introduced an axiomatic system, currently known as S4, for a logic of an absolute provability, i.e. not depending on the formalism chosen ([God 33]). The problem of finding a fair provability model for S4 was left open. The famous formal provability predicate which first appeared in the Gödel Incompleteness Theorem does not do this job: the logic of formal provability is not compatible with S4. As was discovered in [Art 95], this defect of the formal provability (...) predicate can be bypassed by replacing hidden quantifiers over proofs by proof polynomials in a certain finite basis. The resulting Logic of Proofs enjoys a natural arithmetical semantics and provides an intended provability model for S4, thus answering a question left open by Gödel in 1933. Proof polynomials give an intended semantics for some other constructions based on the concept of provability, including intuitionistic logic with its Brouwer- Heyting- Kolmogorov interpretation, ?-calculus and modal ?-calculus. In the current paper we demonstrate how the intuitionistic propositional logic Int can be directly realized by proof polynomials. It is shown, that Int is complete with respect to this proof realizability. (shrink)

The article analyzes the philosophical concept of the “porous self” of J. Rivera. The originality of this concept in the post-phenomenological project is determined by the role of theological constructions that modify the primal experience of self-consciousness. This modification allows us to interpret the phenomenological description of the human self as different from the classical — “porous” temporality, i.e., correlating through “two entrances”—the internal and external—with eternity. Within this approach, the primary phenomenon of the constitution of the "porous" self becomes (...) the inner word, which in the appeal to eternity turns out to be the original self-awareness of the self as a temporality. The secondary phenomenon of the constitution of the “porous” self is not the mundane temporality of M. Heidegger, but Epektasis as an intense striving towards the end of time in General. The worldly temporality of the self, transformed by faith, is phenomenologically revealed as open to eternity in each of its moments. The third phenomenon of the temporality of the self is Memoria, whose interpretation reveals how the structure of the inner consciousness of time by E. Husserl can be framed ontologically and harmoniously integrated into the theological concept. The article shows how, based on this understanding of both the internal and external openness of the “porous” self for eternity, the integral structure of its temporality is formed. The temporality of the porous self is a modification of Husserl’s time diagrams and the intertwining of two streams of temporality at the same time from past to future and from future to past, which itself constitutes a phenomenal field of events of self. This understanding of temporality sets new perspectives for the phenomenological analysis of subjectivity. (shrink)

One of the main fields of consciousness studies is the search for the function of consciousness. The article deals with the hypothesis of the function of imagination as an attribute of consciousness. In the regard of the issues of the attributes of consciousness, the author analyzes the phenomenon of aphantasia, that is, lack of imagination. Despite the lack of formalized ideas about the function of consciousness and despite the scientific trend of the narrowing research areas where subjective experience is necessary (...) for a normal behavior of brain, there is a tendency to expand the presence of consciousness in the world in the modern Western philosophy of consciousness. The result of this “emancipation of consciousness” is the idea of the theoretical essential closeness of a human being and other agents: animals, artificial intelligence, plants. A consequence of the “emancipation of consciousness” is the emergence of modern versions of panpsychism, which propose expanding the space of consciousness to the world as a whole. However, studies in the field of conscious cognitive processes show that the processes that need the participation of consciousness, according to the standard intuitions, in some cases successfully performed without it. For example, the phenomenon of aphantasia shows that the tasks of imagination are performed in the absence of the ability to imagine. Therefore, it is important to take also into account the theoretical possibility of the lack of the realization of the function of consciousness. This makes it possible to ask a question about the presence of consciousness in the space that is traditionally endowed with consciousness, according to the dominant views in philosophy. Therefore, by approaching the question of the attributes of consciousness, the author demonstrates the limitations of the program for the emancipation of consciousness and offers an alternative solution to the question of the scale of the presence of consciousness in the world. (shrink)

Introduction. The article analyzes the problem of substantiating morality in revolutionary activity using the example of L. D. Trotsky’s articles. The relevance of the article is connected with its consideration of ethical ideas, which are largely common to Marxist and generally left-radical philosophy. In addition, the works of L. D. Trotsky that we are considering, for political reasons, entered into free scientific circulation relatively recently, and to date have not received a sufficient amount of versatile academic commentary, primarily philosophical. The (...) purpose of the study is to analyze the position of L. D. Trotsky regarding the use of violence as a means of achieving political goals, to identify the main arguments and principles underlying his approach to this problem, and also to assess its influence on political thought and practice. As a result of the analysis, the authors strive to provide readers with a deeper understanding of the problematic ethical aspects of using violence in politics through the prism of the ideas and views of Leo Trotsky. Methods. The authors use historical and hermeneutic methods. The first allows us to explore the context of the time in which the ethical views of L. D. Trotsky developed, and the second allows us to identify in his texts the basic principles and ideas characteristic of revolutionary radicalism. In addition, general scientific methods were used: analysis, synthesis, comparison and generalization, which made it possible to organize the material, identify patterns and draw conclusions based on a comparison of the ethical views of L. D. Trotsky with various ethical systems, highlighting their strengths and weaknesses in these views. Scientific novelty of the research. The authors focus on the problematic substantiation of morality in the articles of L. D. Trotsky, primarily such as “Terrorism and Communism” (1920) and “Their Morality and Ours” (1938, written in exile). At the same time, Western research on this topic is analyzed, as well as the controversy that unfolded between Trotsky and Bertrand Russell. It is noted that based on the statements of F.M. Dostoevsky that building a just society is impossible with the help of immoral means, since the goal can be transformed depending on the methods of achieving it. The problematic nature of the concept of conscience and possible options for its inadequate interpretation are revealed: (1) when it replaces the moral and metaphysical ideal (I. Kant, L. Tolstoy), or (2) it is completely declared a “chimera”, identified with selfish aspirations, the need to capture and retain power, hiding behind some ideals. It is indicated that the second position is characteristic of L. Trotsky, who tried to “morally” justify total revolutionary violence. Results. The authors come to the conclusion that Trotsky’s position is essentially an extremely utilitarian and revolutionary version of Machiavellianism, when, for the sake of an allegedly good goal, it becomes possible to carry out mass repressions, to sacrifice not only people, but also entire nations. It turned out that sworn political opponents, Stalin and Trotsky, assessed the role of violence in politics in a similar way. At the same time, the launched flywheel of violence cannot be stopped so easily; it destroyed Trotsky himself. Nevertheless, the fact that Trotsky addressed this item speaks to the importance of resolving the moral problems associated with revolutionary practice. (shrink)

'Ontological Semantics' introduces a comprehensive approach to the treatment of text meaning by computer, arguing that being able to use meaning is crucial to the success of natural language processing applications.

Justification Logic provides an axiomatic description of justifications and delegates the question of their nature to semantics. In this note, we address the conceptual issue of the logical type of justifications: we argue that justifications in the logical setting are naturally interpreted as sets of formulas which leads to a class of epistemic models that we call modular models . We show that Fitting models for Justification Logic naturally encode modular models and can be regarded as convenient pre-models of the (...) former. (shrink)

The present paper is devoted to computational aspects of propositional inconsistency-adaptive logics. In particular, we prove (relativized versions of) some principal results on computational complexity of derivability in such logics, namely in cases of CLuN r and CLuN m , i.e., CLuN supplied with the reliability strategy and the minimal abnormality strategy, respectively.

The present study aims to elucidate whether insight problem solving could be facilitated by the cognitive component of humour. The authors take interest in whether the logical mechanisms of humour can affect how fast insight problems are solved. To that end, the authors conducted two experiments where participants solved insight problems after watching visual humorous stimuli such as videos and slideshows. The first experiment demonstrated the overall impact of facilitation by humour on insight problem solving; however, it did not show (...) any difference in how particular logical mechanisms of humour affect the solution time of insight problems. The second experiment showed that the cognitive component of humour could selectively affect insight problems whose difficulty stems from different sources. These results suggest that the cognitive component of humour, when operationalised as logical mechanisms and schema switching, contributes to solving insight problems. (shrink)

The publication of The Use of Bodies, the final volume in Giorgio Agamben’s Homo Sacer series, makes it possible to take stock of Agamben’s project as a whole. Having started with a powerful critique of the biopolitical sovereignty as the essence of modern politics, Agamben concludes his project with an affirmative vision of inoperative politics of form-of-life, in which life is not negated or sacrificed to the privileged form it must attain, but rather remains inseparable from the form that does (...) nothing but express it. The article begins by reconstituting the non-relational logic that Agamben develops in order to render inoperative the existing apparatuses of ontology, ethics and politics. We then address the dimension of lifestyle as a new key domain of Agamben’s work, in which biopolitics may be recast in an affirmative key of form-of-life. While Agamben is better known for sceptical and scornful statements about contemporary liberal democracies, we shall argue that his affirmative biopolitics, characterized by destituent power, resonates with Claude Lefort’s understanding of democracy as structured around the ontological void and epistemic indeterminacy. In the conclusion we question the viability of this biopolitical democracy, focusing on Agamben’s example of the Nocturnal Council in Plato’s Laws. (shrink)

The article takes Giorgio Agamben’s declaration of his optimism with regard to the possibilities of global political transformation as a point of departure for the inquiry into the affirmative aspects of Agamben’s political thought, frequently overshadowed by his more famous critical claims. We reconstitute three principles grounding Agamben’s optimism that pertain respectively to the total crisis of the contemporary biopolitical apparatuses, the possibility of a radically different form-of-life on the basis of their residue and the minimalist character of this transformation (...) that consists entirely in the subtraction of existence from these apparatuses. While the first two principles are unproblematic in the wider context of Agamben’s work, the third principle introduces the problematic of will that remains highly ambiguous in his philosophy. In the remainder of the article we address this ambiguity in an analysis of Agamben’s reading of Melville’s ‘Bartleby the Scrivener’ and conclude that Agamben’s optimism ultimately consists in the affirmation of absolute contingency, beyond both will and necessity. (shrink)

We study unification problem and problem of admissibility for inference rules in minimal Johanssonsʼ logic J and positive intuitionistic logic IPC+. This paper proves that the problem of admissibility for inference rules with coefficients is decidable for the paraconsistent minimal Johanssonsʼ logic J and the positive intuitionistic logic IPC+. Using obtained technique we show also that the unification problem for these logics is also decidable: we offer algorithms which compute complete sets of unifiers for any unifiable formula. Checking just unifiability (...) of formulas with coefficients also works via verification of admissibility. (shrink)

Neuroscience has established several brain pathways that process visual information. Distinct neural circuits analyze body appearance and movement providing information about the person’s cognitive and emotional states. The activity of the pathways depends on the salience of visual stimuli for the organism in the given circumstances. Since ballet performances are not among the crucial events for the viewer’s organism, not all viewers perceive and interpret bodily signs that express the mental state of the dancer. Treatment of the dancer as close (...) other activates the neural circuits that elaborate emotions, this enables the viewer to feel the internal state of the dancer and enrich the interpretation of the scenic action. (shrink)