Speaker: Zhuanghu Liu (Professor, Department of Philosophy, Peking University)

Moderator: Zhan Su (Associate Professor, School of Humanities, University of Chinese Academy of Sciences)

Time: Friday, October 11, 2024, 14:00 - 17:00

Venue: Lecture Hall, Institute of Philosophy, Chinese Academy of Sciences (4th Floor, South Building, Building 4, Software Park, No. 4 Zhongguancun South Street)

Organizers: Institute of Philosophy, Chinese Academy of Sciences; School of Humanities, University of Chinese Academy of Sciences

Abstract:
The formalization of syllogisms has been explored extensively, but most work focuses on the axioms of syllogistic logic (i.e., the 24 valid syllogisms, referred to in this talk as the "standard syllogistic theory") rather than on syllogistic reasoning as a whole. Furthermore, most formalizations embed syllogistic reasoning into other logical systems. For example, Łukasiewicz’s axiomatic system for syllogisms essentially relies on propositional logic.

Aristotle’s work on formalizing syllogisms included an important approach: deriving all 24 valid syllogisms from the AAA form. Aristotle used the method of conversion; without it, both AAA and EAE are needed to derive all valid syllogisms. This talk will analyze the core ideas behind these methods and how they are reflected in formalization. Based on this analysis, the standard syllogistic theory will be generalized into a broader syllogistic theory.

Additionally, the talk introduces a relational model for syllogisms. Using this model, the standard syllogistic theory will be analyzed to demonstrate how it characterizes transitive relations.

Speaker Bio:
Zhuanghu Liu is a Professor and doctoral supervisor at the Department of Philosophy, Peking University. Formerly the head of the logic teaching and research section and a member of the academic committee, he is now retired. After graduating from the Department of Mathematics in 1982, he joined the Department of Philosophy, focusing on mathematical logic. His influential early work includes The Structure of Equi-Degrees and Non-Equi-Degrees and the Separation Properties of Sets in P-T Degrees, which earned him the second prize of the Jin Yuelin Academic Award in 1990.

In 1992, he shifted his focus to philosophical logic, where he initiated original research, notably extending the neighborhood semantics of modal logic to establish a universal neighborhood semantics applicable to various logics, publishing pivotal papers in this area from 1995 onward. His research spans diverse branches of logic, with impactful contributions to inductive logic, cognitive logic, and paradoxes. Recently, he has concentrated on branches related to cognition and language, exploring corresponding philosophical questions alongside his logical investigations.

Professor Liu believes that mathematical logic provides the foundational ideas and methods for modern logic research, essential for any logical branch. While emphasizing the importance of logical techniques, he also advocates attention to related philosophical issues.

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