(The Impossibility of ) Deliberation-Consistent Social Choice

There is now a growing consensus among democratic theorists that we should incorporate both ‘democratic deliberation’ and ‘aggregative voting’ into our democratic processes, where democratic deliberation precedes aggregating people’s votes. But how should the two democratic mechanisms of deliberation and voting interact? The question we wish to ask in this paper is which social choice rules are consistent with successful deliberation once it has occurred. For this purpose, we introduce a new axiom, which we call “Non-Negative Response toward Successful Deliberation (NNRD).” The basic idea is that if some individuals change their preferences toward other individuals’ preferences through successful deliberation, then the social choice rule should not make everybody who has successfully persuaded others through reasoned deliberation worse-off than what s/he would have achieved without deliberation. We prove an impossibility theorem that shows that there exists no aggregation rule that can simultaneously satisfy (NNRD) along with other mild axioms that reflect deliberative democracy’s core commitment to unanimous consensus and democratic equality. We offer potential escape routes: however, it is shown that each escape route can succeed only by compromising some core value of deliberative democracy.