Michael Müller

We develop a novel argument scheme tailored to debates surrounding public votes on a state action. It can be used to propose reasons for voting “yes” or “no” and allows for natural reconstructions of such debates. These reconstructions are of particular use to voters trying to weigh the pros and cons of the proposed state action. The scheme for proposing reasons helps answering two questions: What changes will the proposed state action bring with it? And are these changes good or not? Using the scheme, we derive a three-layered structure of public debates surrounding votes that aides in constructing systematic and comprehensive overviews. The scheme for proposing reasons also lends itself to concise summaries for voter information and can be incorporated into more general deliberation dialogues.

An important appeal of strategy-proofness is the robustness that it implies. Under a strategy-proof voting rule, every individual has an optimal strategy independently of the behavior of all other voters, namely truth-telling. In particular, optimal play is robust with respect to the beliefs voters may have about the type and the behavior of the other voters. Following Blin and Satterthwaite (Economet J Economet Soc 45(4):881–888, 1977), we call this logically weaker property “belief-independence.” In this paper, we give a number of examples of voting rules that are belief-independent but not strategy-proof. However, we also show that belief-independence implies strategy-proofness under a few natural additional conditions. The notion of belief-independence naturally leads to a the strengthening of strategy-proofness to “robust” strategy-proofness which requires that no voter whose true preference may come from a restricted domain can benefit by submitting any unrestricted preference ordering given any unrestricted preference profile for all other voters. There are examples of strategy-proof voting rules (on a restricted domain) that are not robustly strategy-proof, but under natural additional conditions the two properties are shown to be equivalent.