JRC Joint PhD Celebration Event
Tsinghua University – University of Amsterdam Joint Research Center for Logic
12th September 2023
ILLC, Amsterdam + Online
The joint research center for Logic at both Tsinghua University and the University of Amsterdam (UvA) is proud to announce the completion of three new joint PhD theses. Each PhD thesis is the product of a very successful collaboration between our two institutions. The work reported on in these new PhD thesis projects is perfectly aligned with the main mission of the JRC centre to further broaden the interdisciplinary view of logic. We will take the opportunity in the afternoon of the 12th of September to celebrate these new achievements.
We warmly invite all interested researchers and students to attend the event which will take place at the ILLC, University of Amsterdam, Science Park on Tuesday, the 12th of September 2023. This event will be held in hybrid format.
Registration: To participate, please complete the registration form (there is no registration fee)
The new joint PhD theses:
Modality holds a central position in the fields of formal semantics and modal logic. This dissertation delves into epistemic and desiderative modalities, focusing on addressing various monotonicity puzzles in modal contexts.
Two primary topics are investigated throughout the dissertation. The first entails a systematic and unified approach to explain puzzles related to monotonicity in intensional contexts, which manifest as empirical phenomena in natural language. By these puz- zles, monotonic inferences under modal and attitude verbs appear infelicitous, thereby challenging the monotonic semantics of modalities. This dissertation suggests that these puzzles arise from pragmatic effects triggered by the typical underspecified nature of con- clusions reached by monotonic reasoning. In Chapter 4, a comprehensive analysis and a uniform account for this issue is provided.
Another focus of this dissertation is the study of modality. The thesis employs epis- temic and desiderative modalities as examples to examine whether and how the puzzles related to monotonicity influence the semantic and logical properties of the modalities. Firstly, the interactions between knowledge, beliefs, and epistemic possibilities (expressed by the English modal verb might) are systematically investigated. In Chapter 2, a Bilateral State-based Epistemic Logic (BSEL) is proposed, exploring the concepts of knowing and believing an epistemic possibility. Specifically, it investigates the phenomenon of epis- temic might and how its non-classical properties interact with the monotonicity of know and believe.
In Chapter 3, we broaden our discussion to include situations involving multiple agents, aiming to investigate how epistemic modals interact in multi-agent contexts. This extension is motivated by the argument that epistemic might is perspective-sensitive. Con- sequently, when it comes to claims involving epistemic might, different agents may eval- uate them differently, thereby requiring the inclusion of agency as a factor in their inter- pretation.
Chapter 5 shifts its focus towards desiderative modality, proposing a novel logic of desire that incorporates causal inference. This proposal combines the betterness model of preference logic with the causal model of causal inference, resulting in a desire-causality model. Furthermore, a complete logic is developed for this model.
In this dissertation, the treatment of monotonicity and modality is not conducted in isolation, but rather from the standpoint of their interaction. The investigations offer in- sights into the relationship between logic and language, semantics and pragmatics. These findings contribute to our understanding of these interrelated domains.
Games are good models for analyzing crucial notions in logical reasoning and computation. This dissertation specifically delves into game graphs, game board change, and the logical analysis of game elements across various scenarios.
First, we analyze two sorts of games. The first kind of games we consider are sabotage games. We provide a complete axiomatization for the validities in the language of sabotage modal logic slightly extended with just enough expressive devices from hybrid logic.
Our next kind of game, i.e., the distributed game, concerns the difference between players’ internal view and the modeler’s external view of the game as it proceeds. In Chapter 4, we study these ‘distributed games’ with special logical languages allowing us to describe local and global perspectives.
The remaining topics of the thesis explore two further directions.
First, in Chapter 5 we note that the sabotage model logics in our first part can be seen as instances of a much broader class of logics with modalities describing various model changes. We explore what is the precise complexity of testing for the appropriate notions of bisimulation between given finite models.
Our final topic concerns another extension of distributed games for game scenarios, namely, in the functioning of global recommender systems interacting with local individual users. In Chapter 6 we show how the filtration dynamics can be specified and analyzed completely in dynamic-epistemic logics of communication involving filtering actions.
Finally, we highlight some unresolved issues for further exploration based on existing research.
People inhabit a vast and intricate social network nowadays. In addition to our own decisions and actions, we confront those of various groups every day. Collective decisions and actions are more complex and bewildering compared to those made by individuals. As members of a collective, we contribute to its decisions, but our contributions may not always align with the outcome. We may also find ourselves excluded from certain groups and passively subjected to their influences without being aware of the source. We are used to being in overlapping groups and may switch identities, supporting or opposing the claims of particular groups. But rarely do we pause to think: What do we talk about when we talk about groups and their decisions?
At the heart of this dissertation is the question of collective agency, i.e., in what sense can we treat a group as a rational agent capable of its action. There are two perspectives we take: a philosophical and logical one. The philosophical perspective mainly discusses the ontological and epistemological issues related to collective agency, sorts out the relevant philosophical history, and argues that the combination of a relational view of collective agency and a dispositional view of collective intentionality provides a rational and realistic account. The logical perspective is associated with formal theories of groups, it disregards the psychological content involved in the philosophical perspective, establishes a logical system that is sufficiently formal and objective, and axiomatizes the nature of a collective.
The first topic that is addressed is the ontology of collective agency, i.e., the question what exactly is collective agency. The philosophical discussion of collective agency centres around the reduction problem of the concept of a collective. Individualism and Cartesian internalism have long influenced orthodox theories and made them face the choice between an irreducible concept of a collective and ontological reductionism. Heterodox theories such as functionalism and interpretationism reinterpret the concept of agency and accept it as also realized on the level of a collective. To adequately explain social phenomena that are essentially relational in nature, we propose a relational, holistic account of collective agency and argue that functionalism and interpretationism can be integrated into such an account.
While acknowledging the irreducibility of the concept of a collective, we find that there is a deep incompatibility between the concept of a collective and the concept of intentionality as the mark of the mental. To explain how collective intentionality nevertheless is possible and why we tend to use it analogously to how we use the concept of individual intentionality, we explore a dispositional account of intentionality which enables us to give an account of the concept of intentionality at both the individual and collective level. Specifically, we subdivide the dispositional account into three aspects: behavioral, purely mental, and cognitive. We then argue that collective intentionality is real by analyzing different forms of attributive judgments of intentionality and by introducing the perspective of indispensable collective responsibility.
We also analyze how philosophical theories about collective agency relate to central features of formal theories about collective decisions, such as game theory. Although the two fields are both concerned with collectives, there are also differences that need to be addressed. For example, game theory is clearly anti-psychologistic since its aim is a formal and objective analysis. However, from the relational and dispositional perspective, intentionality at the individual level and collective intentionality as we analyze it, inevitably involve mental content. In order to explain this difference and identify where the boundary is, we analyze the relationships between the three basic concepts involved, namely intentionality, preference, and dependency, so as to provide a unified picture of collective theory across philosophical and formal theories.
After paving the nexus between philosophical and formal perspectives, the logical perspective becomes the theme of our discussion. To be able to express game theoretical concepts and to connect them to our philosophical perspective, We present a logic of preference and functional dependence and its hybrid extension, and provide an axiomatization which is sound and strongly complete. The decidability of this logic is also proved. Its application to modeling non-cooperative and cooperative games in strategic form is explored. The resulting framework provides a unified view of Nash equilibrium, Pareto optimality, and the core. The philosophical relevance of these game-theoretical notions to discussions of collective agency is made explicit. Some critical connections with other logics are also revealed, for example, coalition logic, the logic of functional dependence, and the logic of ceteris paribus preference.
Finally, we conclude and clarify the position of our theory in the broader field of research on the topics addressed in the thesis. Also, we point out many new questions and directions suggested by our analysis, including philosophical and logical open problems.
- Workshop Venue: ILLC, room F1.15, SP107, Amsterdam + Online
|Welcome and Opening of the event
|Lei Li "Logics for Personalized Announcements"
|Jialiang Yan "Formalizing and Reasoning Epistemic Might in Multi-agent Scenarios" (online)
|Yiyan Wang "Collective Agency in Change"
|Invited talk by Sujata Ghosh "I Know Where You Are : An Epistemic Study on Hide and Seek Games"
|About the JRC (Johan van Benthem and Fenrong Liu)
|Closing words (Robert van Rooij, director of the ILLC)
|17:30 - 19:00
- Sonja Smets (ILLC, University of Amsterdam)
- Lei Li , Yiyan Wang, Jialiang Yan (Tsinghua + ILLC, University of Amsterdam)
- Sponsor: The event is sponsored by JRC@ILLC