Aula 103 (San Niccolò)
12:00-13:00; 18 Marzo 2025
Prof. Zhaokuan Hao
School of Philosophy – Fudan University – Shanghai, China
Abstract: We are focusing on Plato's method of diairesis. This is a method for discovering definitions of concepts that he developed in a series of dialogues, including Phaedrus, Sophist, Statesman, and Philebus. Interestingly, Gregory Cherlin points out that Saharon Shelah's strategy for dividing lines in contemporary model theory is a mathematical version of Plato's "cutting through the middle." John T. Baldwin puts this more specifically: a dividing line is a property that must be both a "virtuous property" and its negation. In this talk, we will focus on more fundamental philosophical questions: Why do dividing lines exist? How can a philosopher or mathematician be sure that a dividing line has been discovered? The requirements for candidate dividing lines proposed by Shelah and the strategy of using the "test problem" parallel various actual methods of dividing in Plato's dialogues. In essence, these requirements and strategies are actually intended to ensure that Plato's requirement in the Sophist is to divide according to Form, that is, objective concepts as we understand them.