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The Problem of Constrained Judgment Aggregation

Chapter
Part of the The Philosophy of Science in a European Perspective book series (PSEP, volume 1)

Abstract

Group decisions must often obey exogenous constraints. While in a preference aggregation problem constraints are modelled by restricting the set of feasible alternatives, this paper discusses the modelling of constraints when aggregating individual yes/no judgments on interconnected propositions. For example, court judgments in breach-of-contract cases should respect the constraint that action and obligation are necessary and sufficient for liability, and judgments on budget items should respect budgetary constraints. In this paper, we make constraints in judgment aggregation explicit by relativizing the rationality conditions of consistency and deductive closure to a constraint set, whose variation yields more or less strong notions of rationality. This approach of modelling constraints explicitly contrasts with that of building constraints as axioms into the logic, which turns compliance with constraints into a matter of logical consistency and thereby conflates requirements of ordinary logical consistency (such as not to affirm both a proposition and its negation) and requirements dictated by the environment (such as budgetary constraints). We present some general impossibility results on constrained judgment aggregation; they are immediate corollaries of known results on (unconstrained) judgment aggregation.

Keywords

Binary Relation Social Choice Aggregation Function Balance Budget Judgment Aggregation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Netherlands 2010

Authors and Affiliations

  1. 1.Department of Philosophy, Logic and Scientific MethodLondon School of EconomicsLondonUK
  2. 2.Departments of Government and PhilosophyLondon School of EconomicsLondonUK

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