The Common Structure of Paradoxes in Aggregation Theory

Abstract

In this paper we analyse some of the classical paradoxes in Social Choice Theory (namely, the Condorcet paradox, the discursive dilemma, the Ostrogorski paradox and the multiple election paradox) using a general framework for the study of aggregation problems called binary aggregation with integrity constraints. We provide a definition of paradox that is general enough to account for the four cases mentioned, and identify a common structure in the syntactic properties of the rationality assumptions that lie behind such paradoxes. We generalise this observation by providing a full characterisation of the set of rationality assumptions on which the majority rule does not generate a paradox.