Wlodek Rabinowicz suggested in an e-mail conversation (2001) to me that one might be able to use a particular Hats Puzzle to make a Dutch Book against a group of individually rational persons. I present a fanciful story here that has the same structure as Rabinowicz’s Dutch Book.

On the face of it both aggregation and deliberation represent alternative ways of producing a consensus. I argue, however, that the adequacy of aggregation mechanisms should be evaluated with an eye to the effects, both possible and actual, of public deliberation. Such an evaluation is undertaken by sketching a Bayesian model of deliberation as learning from others.