A social choice theory of legitimacy

Abstract

We develop a formal theory of legitimate collective choice. In our theory a policy choice is legitimate if the process through which the final choice was determined is consistent with some principle that can be used to (perhaps partially) rank the potential policy choices. The set of principles in any choice situation is taken to be exogenous, but a decision-making process is defined so as to deal with any nontrivial set of principles. Such a process is itself referred to as legitimate if it is guaranteed to select a legitimate outcome for each possible exogenous set of principles. We characterize the class of procedures that are legitimate, prove that legitimate policy decisions consistent with principles always exist and characterize the set of policy decisions that are legitimate for a any given set of principles. As we do not require the principles to be weak orders of the alternatives, our theory provides a notion of legitimacy that can be satisfied even when the guiding principles are potentially cyclic or incomplete. Accordingly, our theory illustrates one nontautological means by which majoritarian principles can be reconciled with legitimacy.