ILLC-LIRa February 2020

illc-lira@list.uva.nl

1 participants
8 discussions

LIRa session: Dean McHugh
by LIRa Seminar 28 Feb '20

28 Feb '20

Dear all, We will have our next session on Thursday, March 5th. Our speaker is Dean McHugh. Please, find the details below: Speaker: Dean McHugh Date and Time: Thursday, March 5th 2020, 16:30-18:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Causality = time + modality + effective difference-making Abstract. Causal reasoning is the paradigm form of explanatory reasoning, essential to both purposeful action and the scientific method. But an adequate analysis of causal reasoning remains to be found. This talk contributes to the analysis of causal reasoning by seeking to answer two questions that any theory of causality must face. First, what kind of information do we use when we judge that a causal relation holds? That is, what kind of information should models of causality contain? Second, what does it mean for a causal claim to be true? We will address the modelling question by focusing on the role of time and modality, proposing to represent causality via dynamical systems, and comparing the resulting approach to models of causation as directed acyclic graphs (as proposed, for example, by Judea Pearl). We analyze the truth conditions of causal claims by building on the work of Carolina Sartorio, Joseph Halpern and Sander Beckers. In particular, we seek answers to the following two questions: in what sense, if any, do causes ‘make’ their effects occur? And in what sense, if any, do causes ‘make a difference’ to their effects? Hope to see you there! The LIRa team

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LIRa session: Alexandru Baltag
by LIRa Seminar 26 Feb '20

26 Feb '20

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below. Speaker: Alexandru Baltag Date and Time: Thursday, February 27th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Tell Us All You Know Abstract. I analyze the notion of ``epistemic superiority\" between agents or groups (e.g. ``She knows all they know\"), by adding epistemic comparison statements to standard epistemic logic. I show the connection of this notion with the logic of local dependence between variables (as axiomatized in my joint paper with van Benthem, recently presented at LIRa). On the dynamic side, I introduce actions by which epistemic superiority can be acquired: ``sharing all one knows\" (by e.g. giving access to one\'s information database to all or some of the other agents), or ``reading a knowledge base\" (i.e. gaining such access to another\'s information database, regardless of whether or not gave permission). I show that distributed knowledge is necessary to `pre-encode\' what happens to individual knowledge after such actions. As for dealing with common knowledge after these actions, we need to introduce a further generalization: the concept of ``common distributed knowledge\" (described for the first time in my student\'s Suzanne van Wijk\'s MoL thesis). I give an axiomatization of the logic of epistemic comparisons and common distributed knowledge, and I use it as a static base to axiomatize the dynamic logic of public and semi-public sharing/reading events. I move on to more complex such events involving privacy (e.g. hacking), and use an analogue of event models to describe and axiomatize them. I end with some related open questions. This is joint work with Sonja Smets. Hope to see you there! The LIRa team

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LIRa session: Alexandru Baltag
by LIRa Seminar 22 Feb '20

22 Feb '20

Dear all, We will our next LIRa session on Thursday, February 27th. Our speaker is Alexandru Baltag. Please, find the details below: Speaker: Alexandru Baltag Date and Time: Thursday, February 27th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Tell Us All You Know Abstract. I analyze the notion of ``epistemic superiority\" between agents or groups (e.g. ``She knows all they know\"), by adding epistemic comparison statements to standard epistemic logic. I show the connection of this notion with the logic of local dependence between variables (as axiomatized in my joint paper with van Benthem, recently presented at LIRa). On the dynamic side, I introduce actions by which epistemic superiority can be acquired: ``sharing all one knows\" (by e.g. giving access to one\'s information database to all or some of the other agents), or ``reading a knowledge base\" (i.e. gaining such access to another\'s information database, regardless of whether or not gave permission). I show that distributed knowledge is necessary to `pre-encode\' what happens to individual knowledge after such actions. As for dealing with common knowledge after these actions, we need to introduce a further generalization: the concept of ``common distributed knowledge\" (described for the first time in my student\'s Suzanne van Wijk\'s MoL thesis). I give an axiomatization of the logic of epistemic comparisons and common distributed knowledge, and I use it as a static base to axiomatize the dynamic logic of public and semi-public sharing/reading events. I move on to more complex such events involving privacy (e.g. hacking), and use an analogue of event models to describe and axiomatize them. I end with some related open questions. This is joint work with Sonja Smets. Hope to see you there! The LIRa team

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LIRa session: Maria Aloni
by LIRa Seminar 19 Feb '20

19 Feb '20

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Maria Aloni Date and Time: Thursday, February 20th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Pragmatic enrichments in bilateral state-based modal logic. Abstract. In a state-based modal logic, formulas are interpreted with respect to sets of possible worlds in a Kripke model rather than single worlds. In the talk I will present a bilateral version of a state-based modal logic motivated by linguistic phenomena at the semantics-pragmatics interface (including epistemic contradictions, free choice and ignorance inference). After defining the model theory and discussing some of the linguistic applications, I will present some (negative) results concerning modal definability and a first attempt towards an axiomatisation. Hope to see you there! The LIRa team

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LIRa session: Maria Aloni
by LIRa Seminar 14 Feb '20

14 Feb '20

Dear all, We will have our next LIRa session on Thursday, February 20th. Our speaker is Maria Aloni. Please, find the details below Speaker: Maria Aloni Date and Time: Thursday, February 20th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Pragmatic enrichments in bilateral state-based modal logic. Abstract. In a state-based modal logic, formulas are interpreted with respect to sets of possible worlds in a Kripke model rather than single worlds. In the talk I will present a bilateral version of a state-based modal logic motivated by linguistic phenomena at the semantics-pragmatics interface (including epistemic contradictions, free choice and ignorance inference). After defining the model theory and discussing some of the linguistic applications, I will present some (negative) results concerning modal definability and a first attempt towards an axiomatisation. Hope to see you there! The LIRa team

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LIRa session: Declan Thompson
by LIRa Seminar 12 Feb '20

12 Feb '20

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below. Speaker: Declan Thompson Date and Time: Thursday, February 13th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Local Fact Change, Memory Logic and Expressive Power Abstract. Local fact change logic (LFC) models the notion of a unilateral change in a network structure. It adds a single, innocent-looking model change operator to the basic modal logic, allowing the valuation at a single point in the model to change. This small addition results in undecidability, which can quickly be shown via a satisfaction-preserving translation from memory logic (ML). The lack of a direct translation raises the question of the relative expressive power of LFC and ML. In this talk, I will investigate the relative expressive power of LFC and ML. Such comparisons are often made by either providing a direct translation from one logic to the other, or demonstrating a pair of models which one of the logics can distinguish and the other cannot. In the case of LFC and ML, these two approaches come apart. We are left with a somewhat messy picture of how the two compare. Hope to see you there! The LIRa team

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LIRa session: Declan Thompson
by LIRa Seminar 07 Feb '20

07 Feb '20

Dear all, We will have our next LIRa session on Thursday, February 13, usual time. Our speaker is Declan Thompson. Please, find the details below: Speaker: Declan Thompson Date and Time: Thursday, February 13th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Local Fact Change, Memory Logic and Expressive Power Abstract. Local fact change logic (LFC) models the notion of a unilateral change in a network structure. It adds a single, innocent-looking model change operator to the basic modal logic, allowing the valuation at a single point in the model to change. This small addition results in undecidability, which can quickly be shown via a satisfaction-preserving translation from memory logic (ML). The lack of a direct translation raises the question of the relative expressive power of LFC and ML. In this talk, I will investigate the relative expressive power of LFC and ML. Such comparisons are often made by either providing a direct translation from one logic to the other, or demonstrating a pair of models which one of the logics can distinguish and the other cannot. In the case of LFC and ML, these two approaches come apart. We are left with a somewhat messy picture of how the two compare. Hope to see you there! The LIRa team

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LIRa session: Johan van Benthem
by LIRa Seminar 05 Feb '20

05 Feb '20

Dear all, Tomorrow we will have our next LIRa session. Please, find the details below: Speaker: Johan van Benthem Date and Time: Thursday, February 6th 2020, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: A Minimal Classical Logic of Functional Dependence Abstract. Dependence is a ubiquitous notion in science and daily life, and several logical approaches exist for capturing its basic properties. In this talk, we analyze dependence reasoning using a simple decidable logic of functional dependence LFD, based on an extension of classical propositional logic with dependence atoms and dependence quantifiers, modeled in the setting of generalized assignment semantics for FOL. The logic’s expressive strength, complete proof calculus and meta-properties are sketched. Also some language extensions are explored, as well as boundaries with undecidable logics for independence. Finally, connections are discussed with more concrete settings for dependence, including linear dependence in vector spaces, and temporal dependence in dynamical systems and games. Further technical details and topics will be presented by Alexandru Baltag in a follow-up LIRA talk. Hope to see you there! The LIRa team

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ILLC-LIRa February 2020