Abstract

ABSTRACT The notion of consensus plays an important epistemological role in modern welfare economics, in that unanimous consent is a (unique) conceptual test for those changes that are ‘Pareto-desirable’ (that is, make someone better off and no-one else worse). In this paper, we seek to show that unanimous consent does not logically imply Pareto-desirability—that a rational individual may fail to veto policy changes that make him/her worse off. The central element in the proof of this proposition is the observation that in social agreements involving a significant number of participants, any one individual's veto is decisive if it is the only veto. If the individual does not expect to be decisive, he will rationally exercise his vote ‘expressively’, and without sole regard to its consequences. When all individuals so act, a sort of prisoners' dilemma interaction may emerge, even under explicit consensus.