Economics and Philosophy

Essay

JUDGMENT AGGREGATION AND SUBJECTIVE DECISION-MAKING*

Michael K. Millera1

a1 Princeton University

Abstract

I present an original model in judgment aggregation theory that demonstrates the general impossibility of consistently describing decision-making purely at the group level. Only a type of unanimity rule can guarantee a group decision is consistent with supporting reasons, and even this possibility is limited to a small class of reasoning methods. The key innovation is that this result holds when individuals can reason in different ways, an allowance not previously considered in the literature. This generalizes judgment aggregation to subjective decision situations, implying that the discursive dilemma persists without individual agreement on the logical constraints. Notably, the model mirrors the typical method of choosing political representatives, and thus suggests that no voting procedure other than unanimity rule can guarantee representation that reflects electorate opinion. Finally, I apply the results to a normative argument for unanimity rule in contract theory and juries, as well as to problems posed for deliberative democratic theory and the concept of representation.

Footnotes

* Thanks to Christian List for introducing me to the subject of judgment aggregation. Thanks also to Torun Dewan, Jessica Flanigan, Sarah Goff, Lisa Camner, Jared Klyman, Javier Hidalgo, Ben Lauderdale, Christine Percheski, Daniel Osherson, and Franz Dietrich, as well as Editor Luc Bovens and two anonymous reviewers, for their comments.