Acyclic choice and group veto

The Arrow Impossibility Theorem assumes transitivity. Acyclicity is a more appropriate rationality condition for collective decision procedures. Many impossibility theorems for acyclic choice need to assume that there are more alternatives than individuals. In this paper we show that by considering circumstances under which groups (or coalitions) have veto it is possible to prove impossiblity theorems without making such an assumption. Our results extend recent theorems by Blau and Deb, and Blair and Pollak.I would like to thank my research supervisor Amartya Sen, the referee and the editor of this journal for their comments on earlier drafts of this paper.