A liberal paradox for judgment aggregation

In the emerging literature on judgment aggregation over logically connected propositions, expert rights or liberal rights have not been investigated yet. A group making collective judgments may assign individual members or subgroups with expert knowledge on, or particularly affected by, certain propositions the right to determine the collective judgment on those propositions. We identify a problem that generalizes Sen’s ‘liberal paradox’. Under plausible conditions, the assignment of rights to two or more individuals or subgroups is inconsistent with the unanimity principle, whereby unanimously accepted propositions are collectively accepted. The inconsistency can be avoided if individual judgments or rights satisfy special conditions. Earlier versions of this paper were presented at the LGS-4 Conference in Caen, June 2005, and at the World Congress of the Econometric Society in London, August 2005. We are grateful for the comments we received at both occasions as well as from anonymous referees. Franz Dietrich acknowledges financial support from the European Commission-DG Research Sixth Framework Programme (CIT-2-CT-2004-506084 / Polarization and Conflict Project). Christian List acknowledges the hospitality of the Social and Political Theory Program, RSSS, Australian National University.