Time: Wed 13 May 2026, at 15:10

Place: Room 109, Building 3, Lee Shau Kee Humanities Hall

Speaker: FAN Yao, Sun Yat-sen University

This event is part of the Seminar Series on Frontier Issues in Logic.

Abstract:

The Condorcet Jury Theorem (CJT) was originally proposed by Marquis de Condorcet in 1785, and was later expanded and developed in the second half of the twentieth century by scholars such as Duncan Black and Peyton Young, becoming one of the most important theorems in the field of social epistemology. The theorem states that, under the three assumptions of honesty, competence, and independence, collective cognitive decision-making can effectively converge toward truth.

In recent years, the basic assumptions of the theorem have been widely discussed in political theory, economics, philosophy, and related disciplines. Since David Austen-Smith and Jeffrey S. Banks (1996), economists have generally rejected the assumption of honesty. More recent philosophical studies, while focusing on the tension between the assumptions of competence and independence, have continued to uphold the honesty assumption. My recent work offers an in-depth analysis of the roots of this disagreement: economists have unreflectively applied Nash Equilibrium to the CJT framework. By examining the conditions under which Nash equilibrium is applicable, one can see that it is in fact unsuitable for the CJT, thereby allowing the honesty assumption to be defended. In addition, I propose using another solution concept, Focal Point, to understand individual behavior within the CJT framework.

This work provides an opportunity to reconsider the many dimensions of collective decision-making. From the perspective of social epistemology, this lecture will explore a range of issues related to the CJT and collective decision-making, including but not limited to: the cognitive burdens borne by individuals in group decision-making, the relationship and tension between competence and independence, the use and interpretation of formal theories, and the roots of disagreement between individuals etc..