World Logic Day Workshop 2025

World Logic Day Workshop 2025

Introduction:

The World Logic Day Workshop 2025 serves as a platform to celebrate World Logic Day and explore the diverse applications of logic across various disciplines. By inviting scholars from different fields in Hong Kong, we aim to foster interdisciplinary dialogue and collaboration, highlighting the relevance of logical frameworks in contemporary research.

Date & Time:

10^th January (Friday) 2025, 9:00 a.m. to 6:00 p.m.

Venue:

WLB211, Shaw Campus

Enquries:

pangtinkuen@life.hkbu.edu.hk

Speakers:

• Prof. HAWKE, Peter Michael (Lingnan University)
• Prof. LO, Tien-Chun (The Chinese University of Hong Kong)
• Prof. PIETARINEN, Ahti-Veikko (Hong Kong Baptist University)
• Prof. ZHANG, Jiji (The Chinese University of Hong Kong)
• Mr. LIN, Zerong (Hong Kong Baptist University)
• Mr. PANG, Tin Kuen (Hong Kong Baptist University)
• Mr. YANG, Hao (The Chinese University of Hong Kong)
• Mr. YU, Sibo (The Chinese University of Hong Kong)

Schedule

9:00-9:15: Opening Ceremony

9:15-10:00: ZHANG Jiji - Abstract Do-calculus 

10:05-10:50: YU Sibo - Modeling Higher-Order Uncertainty 

10:55-11:40: YANG Hao - Computability, Modal Idealization, and Determinate Arithmetic

11:45-13:30: Lunch - Bistro NTT (Dr. Ng Tor Tai International House, G/F)

13:30-14:15: LO Tien-Chun - Symmetry Lost: An Anselmian Argument for Atheism (co-authored with Peter Fritz (University College London) and Joseph Schmid (Princeton University))

14:20-15:05: Peter Michael HAWKE - An Acceptance Semantics for Stable Modal Knowledge

15:10-15:55: LIN Zerong - Are There Abstract Mathematical Entities?

15:55-16:10: Tea Break

16:10-16:55: PANG Tin Kuen - Simplicity of Proof-Theoretic Semantics for Natural Logic

17:00-17:45: Ahti-Veikko PIETARINEN - Monadic Existential Graphs: Logic and Algebra

17:45-18:00 Closing Remark

Title and Abstract

Abstract Do-calculus

ZHANG Jiji, The Chinese University of Hong Kong

I outline a way to develop an abstract version of Judea Pearl's celebrated do-calculus for identifying intervention effects, using category theory. The abstract version reveals the "causal core" of the do-calculus, which can be formulated as a single master rule about the composablility of causal processes.

Modeling Higher-Order Uncertainty

YU Sibo, The Chinese University of Hong Kong

In this presentation, I will begin with a brief introduction to how formal epistemologists model higher-order epistemic uncertainty. The models involved are called modal probabilistic models. These models aim to represent the epistemic situation of an agent at a given time.

Using these models, many epistemologists have recently been investigating a phenomenon known as higher-order uncertainty. An agent experiences higher-order uncertainty when they are uncertain how much confidence is rational for them to hold regarding a particular subject matter. Our central question is whether such higher-order uncertainty can be rational.

For example, consider you are uncertain about whether it will rain in Hong Kong on May 25 next year. Formal epistemologists typically assign a real number, say 0.8, to represent your confidence in this proposition. If you experience higher-order uncertainty, you would be uncertain about which number represents the degree of belief that is rational for you to hold.

I will conclude my presentation by examining the philosophical implications of allowing rational higher-order uncertainty. Specifically, I will investigate its connections with (i) reflection principles; (ii) evidence externalism; and (ii) the value of evidence.

Computability, Modal Idealization, and Determinate Arithmetic

YANG Hao, The Chinese University of Hong Kong

This paper aims to defend the viability of the computationalist approach (CA) to address the longstanding philosophical challenge to the determinacy of arithmetic, particularly the referential determinacy from arithmetical language to the standard structure of natural numbers. This challenge, akin to Putnam’s famous challenge to moderate realism, underscores the explanatory puzzle posed by the existence of non-standard models and the naturalistic constraints on human’s capacity. CA adopts Church-Turing Thesis (CTT) and Tannenbaum theorem to pin down the reference to the standard structure. But recently, authors criticize that CA falls prey to a dilemma: our grasp of the notion of effective computability either violates naturalistic constraints, or circularly involves arithmetical vocabulary at issue. In defense of CA, I refute the last disjunct by developing a purely modal analysis of the notion of effective computability. Then, there is no reason to believe that effective computability inevitably involves arithmetical vocabulary. And I conclude that CA is still a viable but not #nal solution to the Putnamian challenge to arithmetical determinacy.

Symmetry Lost: An Anselmian Argument for Atheism

LO Tien-Chun, The Chinese University of Hong Kong

(co-authored with Peter Fritz (University College London) and Joseph Schmid (Princeton University))

The modal ontological argument for God’s (necessary) existence faces the problem that a seemingly equally plausible reverse modal ontological argument can be given for God’s (necessary) non-existence. This problem arises from the inconsistency of conjoining the arguments’ premises together in modal system KTB. We propose resolving this inconsistency not by rejecting one of the premises but by weakening KTB. If this solution is accepted, then there is an interesting new logical asymmetry between modal ontological arguments for theism and reverse modal ontological arguments for atheism that favors the latter over the former. Our proposed solution therefore represents a new pathway to atheism.

An Acceptance Semantics for Stable Modal Knowledge

Peter Michael HAWKE, Lingnan University

We observe some puzzling linguistic data concerning ordinary knowledge ascriptions that embed an epistemic (im)possibility claim. We conclude that it is untenable to jointly endorse both classical logic and a pair of intuitively attractive theses: the thesis that knowledge ascriptions are always veridical and a ‘negative transparency’ thesis that reduces knowledge of a simple negated ‘might’ claim to an epistemic claim without modal content. We motivate a strategy for answering the trade-off: preserve veridicality and (generalized) negative transparency, while abandoning the general validity of contraposition. We survey and criticize various approaches to incorporating veridicality into domain semantics, a paradigmatic ‘information-sensitive’ framework for capturing negative transparency and, more generally, the non-classical behavior of sentences with epistemic modals. We then present a novel information-sensitive semantics that successfully executes our favored strategy: stable acceptance semantics.

Are There Abstract Mathematical Entities?

LIN Zerong, Hong Kong Baptist University

Simplicity of Proof-Theoretic Semantics for Natural Logic

PANG Tin Kuen, Hong Kong Baptist University

This presentation aims to introduce and defend proof-theoretic semantics (PTS) for natural logic. PTS, different from model-theoretic semantics (MTS), aims to define the meaning of linguistic expression in terms of proof rather than truth. Due to the criticism of MTS from Nissim Francez, I advocate that PTS has various theoretical advantages, especially its simplicity, compared to MTS for natural logic. In this presentation, I will first introduce natural logic and PTS first. Then, I will defend PTS by (1) demonstrating Nissim Francez's framework of PTS for monotonicity, and (2) extending Peter Ludlow's argument about simplicity of linguistic theory to natural logic.

Monadic Existential Graphs: Logic and Algebra

Ahti-Veikko PIETARINEN, Hong Kong Baptist University