A liberal paradox for judgment aggregation

In the emerging literature on judgment (as opposed to preference) aggregation, expert rights or liberal rights have not been investigated yet. When a group forms collective beliefs, it may assign group members with expert knowledge on certain propositions the right to determine the collective judgment on those propositions; and, when a group forms collective goals or desires, it may assign members specially affected by certain propositions similar rights on those propositions. We identify a problem similar to Sen’s ‘liberal paradox’: Under plausible conditions, the assignment of such rights to two or more individual group members (or subgroups) is inconsistent with the unanimity principle, whereby propositions accepted by all individuals must be collectively accepted. So a group respecting its members’ expert or liberal rights on certain propositions must sometimes overrule its unanimous judgments on others. The inconsistency does not arise if either different individuals’ rights are ‘disconnected’ or individuals are ‘agnostic/tolerant’ or ‘deferring/empathetic’ towards other individuals’ rights. Our findings have implications for the design of mechanisms by which groups (societies, committees, expert panels, organizations) can reach decisions on systems of interconnected propositions.