Judgment aggregation without full rationality
Several recent results on the aggregation of judgments over logically connected propositions show that, under certain conditions, dictatorships are the only propositionwise aggregation functions generating fully rational (i.e., complete and consistent) collective judgments. A frequently mentioned route to avoid dictatorships is to allow incomplete collective judgments. We show that this route does not lead very far: we obtain oligarchies rather than dictatorships if instead of full rationality we merely require that collective judgments be deductively closed, arguably a minimal condition of rationality, compatible even with empty judgment sets. We derive several characterizations of oligarchies and provide illustrative applications to Arrowian preference aggregation and Kasher and Rubinstein’s group identification problem.
KeywordsAggregation Function Full Rationality Agenda Condition Impossibility Result Judgment Aggregation
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- Dietrich F, List C (2007b) Judgment aggregation by quota rules: majority voting generalized. J Theor Polits 19(4) (in press)Google Scholar
- Dietrich F, List C (2007c) Strategy-proof judgment aggregation. Econ Philos (in press)Google Scholar
- Dokow E, Holzman R (2005) Aggregation of binary evaluations. Working paper, Technion Israel Institute of TechnologyGoogle Scholar
- Dokow E, Holzman R (2006) Aggregation of binary evaluations with abstentions. Working paper, Technion Israel Institute of TechnologyGoogle Scholar
- Kasher A, Rubinstein A (1997) On the Question “Who is a J?”: a social choice approach. Log Anal 160:385–395Google Scholar
- List C (2007) Which worlds are possible? A judgment aggregation problem. J Philosophical Logic (in press)Google Scholar
- List C, Pettit P (2002) Aggregating sets of judgments: an impossibility result. Econ Philos 18:89–110Google Scholar
- Mongin P (2005) Factoring out the impossibility of logical aggregation. Working paper, CNRS, ParisGoogle Scholar
- Nehring K, Puppe C (2002) Strategy-proof social choice on single-peaked domains: possibility, impossibility and the space between. Working paper, University of California at DaviesGoogle Scholar
- Nehring K, Puppe C (2005) Consistent judgment aggregation: a characterization. Working paper, University of KarlsruheGoogle Scholar