Arrow's Theorem in Judgment Aggregation

Abstract

In response to recent work on the aggregation of individual judgments on logically connected propositions into collective judgments, it is often asked whether judgment aggregation is a special case of Arrowian preference aggregation. We argue the op- posite. After proving a general impossibility result on judgment aggregation, we construct an embedding of preference aggregation into judgment aggregation and prove Arrow's theorem as a corollary of our result. Although we provide a new proof of Arrow's theorem, our main aim is to identify the analogue of Arrow's theorem in judgment aggregation, to clarify the relation between judgment and preference aggregation and to illustrate the generality of the judgment aggregation model.

JEL Classification: D70, D71